zig/stage0/astgen.c

// astgen.c — AST to ZIR conversion, ported from lib/std/zig/AstGen.zig.
//
// Structural translation of AstGen.zig into C.
// Each function corresponds to a Zig function with the same name,
// with line references to Zig 0.15.1 AstGen.zig.

#include "astgen.h"
#include "common.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>

// --- Declaration.Flags.Id enum (Zir.zig:2724) ---

typedef enum {
    DECL_ID_UNNAMED_TEST,
    DECL_ID_TEST,
    DECL_ID_DECLTEST,
    DECL_ID_COMPTIME,
    DECL_ID_CONST_SIMPLE,
    DECL_ID_CONST_TYPED,
    DECL_ID_CONST,
    DECL_ID_PUB_CONST_SIMPLE,
    DECL_ID_PUB_CONST_TYPED,
    DECL_ID_PUB_CONST,
    DECL_ID_EXTERN_CONST_SIMPLE,
    DECL_ID_EXTERN_CONST,
    DECL_ID_PUB_EXTERN_CONST_SIMPLE,
    DECL_ID_PUB_EXTERN_CONST,
    DECL_ID_EXPORT_CONST,
    DECL_ID_PUB_EXPORT_CONST,
    DECL_ID_VAR_SIMPLE,
    DECL_ID_VAR,
    DECL_ID_VAR_THREADLOCAL,
    DECL_ID_PUB_VAR_SIMPLE,
    DECL_ID_PUB_VAR,
    DECL_ID_PUB_VAR_THREADLOCAL,
    DECL_ID_EXTERN_VAR,
    DECL_ID_EXTERN_VAR_THREADLOCAL,
    DECL_ID_PUB_EXTERN_VAR,
    DECL_ID_PUB_EXTERN_VAR_THREADLOCAL,
    DECL_ID_EXPORT_VAR,
    DECL_ID_EXPORT_VAR_THREADLOCAL,
    DECL_ID_PUB_EXPORT_VAR,
    DECL_ID_PUB_EXPORT_VAR_THREADLOCAL,
} DeclFlagsId;

// --- Import tracking (AstGen.zig:265) ---

typedef struct {
    uint32_t name; // NullTerminatedString index
    uint32_t token; // Ast.TokenIndex
} ImportEntry;

// --- AstGen internal context (mirrors AstGen struct, AstGen.zig:153) ---

typedef struct {
    const Ast* tree;
    ZirInstTag* inst_tags;
    ZirInstData* inst_datas;
    uint32_t inst_len;
    uint32_t inst_cap;
    uint32_t* extra;
    uint32_t extra_len;
    uint32_t extra_cap;
    uint8_t* string_bytes;
    uint32_t string_bytes_len;
    uint32_t string_bytes_cap;
    // String dedup table: stores positions in string_bytes that are
    // registered for deduplication (mirrors AstGen.string_table).
    // Only strings added via identAsString/strLitAsString (non-embedded-null)
    // are registered. Multiline strings are NOT registered.
    uint32_t* string_table;
    uint32_t string_table_len;
    uint32_t string_table_cap;
    uint32_t source_offset;
    uint32_t source_line;
    uint32_t source_column;
    ImportEntry* imports;
    uint32_t imports_len;
    uint32_t imports_cap;
    // Shared dynamic array for GenZir instructions (AstGen.zig:11796).
    // Sub-blocks share this array and track their slice via
    // instructions_top.
    uint32_t* scratch_instructions;
    uint32_t scratch_inst_len;
    uint32_t scratch_inst_cap;
    // Scratch extra array for call arguments (mirrors AstGen.scratch in Zig).
    // Used to collect body lengths + body instructions before copying to
    // extra.
    uint32_t* scratch_extra;
    uint32_t scratch_extra_len;
    uint32_t scratch_extra_cap;
    // Return type ref for the current function (set during fnDecl/testDecl).
    uint32_t fn_ret_ty; // ZirInstRef
    // Pointer to the fn_block GenZir for the current function (AstGen.zig:45).
    void* fn_block; // GenZir*
    // ref_table: deferred REF instructions (AstGen.zig:58-68).
    // Key = operand inst index, Value = ref inst index.
    uint32_t* ref_table_keys;
    uint32_t* ref_table_vals;
    uint32_t ref_table_len;
    uint32_t ref_table_cap;
    // nodes_need_rl: set of AST node indices that need result locations.
    // Populated by astRlAnnotate() pre-pass (AstRlAnnotate.zig).
    uint32_t* nodes_need_rl;
    uint32_t nodes_need_rl_len;
    uint32_t nodes_need_rl_cap;
    bool has_compile_errors;
    bool within_fn; // AstGen.zig:49
    bool fn_var_args; // AstGen.zig:46
} AstGenCtx;

static void setCompileError(AstGenCtx* ag) { ag->has_compile_errors = true; }
#define SET_ERROR(ag) setCompileError(ag)

// Set fn_block pointer on AstGenCtx. The caller is responsible for saving
// and restoring the previous value before the pointed-to GenZir goes out
// of scope (AstGen.zig:45).
static void setFnBlock(AstGenCtx* ag, void* block) { ag->fn_block = block; }

// --- ref_table operations (AstGen.zig:58-68) ---
// Simple linear-scan hash table for deferred REF instructions.

// Returns pointer to existing value if key found, NULL if not found.
static uint32_t* refTableGet(AstGenCtx* ag, uint32_t key) {
    for (uint32_t i = 0; i < ag->ref_table_len; i++) {
        if (ag->ref_table_keys[i] == key)
            return &ag->ref_table_vals[i];
    }
    return NULL;
}

// getOrPut: returns pointer to value slot; sets *found to true if existed.
static uint32_t* refTableGetOrPut(AstGenCtx* ag, uint32_t key, bool* found) {
    for (uint32_t i = 0; i < ag->ref_table_len; i++) {
        if (ag->ref_table_keys[i] == key) {
            *found = true;
            return &ag->ref_table_vals[i];
        }
    }
    *found = false;
    if (ag->ref_table_len >= ag->ref_table_cap) {
        uint32_t new_cap = ag->ref_table_cap == 0 ? 16 : ag->ref_table_cap * 2;
        ag->ref_table_keys
            = realloc(ag->ref_table_keys, new_cap * sizeof(uint32_t));
        ag->ref_table_vals
            = realloc(ag->ref_table_vals, new_cap * sizeof(uint32_t));
        ag->ref_table_cap = new_cap;
    }
    uint32_t idx = ag->ref_table_len++;
    ag->ref_table_keys[idx] = key;
    return &ag->ref_table_vals[idx];
}

// fetchRemove: if key exists, remove it and return true with *val set.
static bool refTableFetchRemove(AstGenCtx* ag, uint32_t key, uint32_t* val) {
    for (uint32_t i = 0; i < ag->ref_table_len; i++) {
        if (ag->ref_table_keys[i] == key) {
            *val = ag->ref_table_vals[i];
            // Swap with last element.
            ag->ref_table_len--;
            if (i < ag->ref_table_len) {
                ag->ref_table_keys[i] = ag->ref_table_keys[ag->ref_table_len];
                ag->ref_table_vals[i] = ag->ref_table_vals[ag->ref_table_len];
            }
            return true;
        }
    }
    return false;
}

// --- Result location (AstGen.zig:11808) ---
// Simplified version of ResultInfo.Loc.
// Defined here (before GenZir) because GenZir.break_result_info uses it.

// ResultInfo.Context (AstGen.zig:371-386).
typedef enum {
    RI_CTX_NONE,
    RI_CTX_RETURN,
    RI_CTX_ERROR_HANDLING_EXPR,
    RI_CTX_SHIFT_OP,
    RI_CTX_FN_ARG,
    RI_CTX_CONST_INIT,
    RI_CTX_ASSIGNMENT,
} ResultCtx;

// DestructureComponent: mirrors Zig's ResultInfo.Loc.DestructureComponent.
typedef enum {
    DC_DISCARD,
    DC_TYPED_PTR,
    DC_INFERRED_PTR,
} DestructureComponentTag;

typedef struct {
    DestructureComponentTag tag;
    uint32_t inst; // ZIR inst ref (for DC_TYPED_PTR and DC_INFERRED_PTR).
    uint32_t src_node; // Only for DC_TYPED_PTR.
} DestructureComponent;

typedef enum {
    RL_NONE, // Just compute the value.
    RL_REF, // Compute a pointer to the value.
    RL_DISCARD, // Compute but discard (emit ensure_result_non_error).
    RL_TY, // Coerce to specific type.
    RL_COERCED_TY, // Coerce to specific type, result is the coercion.
    RL_PTR, // Store result to typed pointer. data=alloc inst, src_node=node.
    RL_INFERRED_PTR, // Store result to inferred pointer. data=alloc inst.
    RL_REF_COERCED_TY, // Ref with pointer type. data=ptr_ty_inst.
    RL_DESTRUCTURE, // Destructure into multiple pointers.
} ResultLocTag;

typedef struct {
    ResultLocTag tag;
    uint32_t data; // ZirInstRef: ty_inst for TY/COERCED_TY, alloc inst for
                   // PTR/INFERRED_PTR.
    uint32_t src_node; // Used for RL_PTR and RL_DESTRUCTURE.
    ResultCtx ctx; // ResultInfo.Context (AstGen.zig:371).
    DestructureComponent* components; // Only for RL_DESTRUCTURE.
    uint32_t components_len; // Only for RL_DESTRUCTURE.
} ResultLoc;

#define RL_NONE_VAL                                                           \
    ((ResultLoc) { .tag = RL_NONE,                                            \
        .data = 0,                                                            \
        .src_node = 0,                                                        \
        .ctx = RI_CTX_NONE,                                                   \
        .components = NULL,                                                   \
        .components_len = 0 })
#define RL_REF_VAL                                                            \
    ((ResultLoc) { .tag = RL_REF,                                             \
        .data = 0,                                                            \
        .src_node = 0,                                                        \
        .ctx = RI_CTX_NONE,                                                   \
        .components = NULL,                                                   \
        .components_len = 0 })
#define RL_DISCARD_VAL                                                        \
    ((ResultLoc) { .tag = RL_DISCARD,                                         \
        .data = 0,                                                            \
        .src_node = 0,                                                        \
        .ctx = RI_CTX_NONE,                                                   \
        .components = NULL,                                                   \
        .components_len = 0 })
#define RL_IS_REF(rl) ((rl).tag == RL_REF || (rl).tag == RL_REF_COERCED_TY)

// --- Scope types (AstGen.zig:11621-11768) ---

typedef enum {
    SCOPE_GEN_ZIR,
    SCOPE_LOCAL_VAL,
    SCOPE_LOCAL_PTR,
    SCOPE_DEFER_NORMAL,
    SCOPE_DEFER_ERROR,
    SCOPE_NAMESPACE,
    SCOPE_TOP,
    SCOPE_LABEL,
} ScopeTag;

typedef struct Scope {
    ScopeTag tag;
} Scope;

// --- GenZir scope (mirrors GenZir struct, AstGen.zig:11772) ---
//
// Sub-blocks share the parent AstGenCtx's scratch_instructions array and
// record their starting offset (instructions_top). This mirrors the upstream
// GenZir.instructions / instructions_top design (AstGen.zig:11796-11850).

typedef struct {
    Scope base; // tag = SCOPE_GEN_ZIR
    Scope* parent;
    AstGenCtx* astgen;
    uint32_t decl_node_index;
    uint32_t decl_line;
    bool is_comptime;
    bool is_inline; // true for inline for/while, labeled blocks in comptime
    bool c_import; // true inside @cImport block
    bool is_typeof; // true inside @TypeOf scope
    uint32_t instructions_top; // start index in shared array
    uint32_t break_block; // UINT32_MAX = none (AstGen.zig:11780)
    uint32_t continue_block; // UINT32_MAX = none (AstGen.zig:11784)
    // Label for labeled blocks (AstGen.zig:11800, 11869-11874).
    uint32_t label_token; // UINT32_MAX = no label
    uint32_t label_block_inst; // the BLOCK instruction index
    ResultLoc break_result_info; // RL for break values
    uint32_t any_defer_node; // UINT32_MAX = none (AstGen.zig:11812)
} GenZir;

// Scope.LocalVal (AstGen.zig:11682).
// This is always a `const` local and the `inst` is a value type, not a
// pointer.
typedef struct {
    Scope base; // tag = SCOPE_LOCAL_VAL
    Scope* parent;
    GenZir* gen_zir;
    uint32_t inst; // ZirInstRef
    uint32_t token_src; // Ast.TokenIndex
    uint32_t name; // NullTerminatedString (string table index)
    bool* is_used_or_discarded; // NULL if not tracking (AstGen.zig:11691)
} ScopeLocalVal;

// Scope.LocalPtr (AstGen.zig:11704).
// This could be a `const` or `var` local. It has a pointer instead of a value.
typedef struct {
    Scope base; // tag = SCOPE_LOCAL_PTR
    Scope* parent;
    GenZir* gen_zir;
    uint32_t ptr; // ZirInstRef
    uint32_t token_src; // Ast.TokenIndex
    uint32_t name; // NullTerminatedString (string table index)
    bool maybe_comptime;
} ScopeLocalPtr;

// Scope.Defer (AstGen.zig:11741).
typedef struct {
    Scope base; // tag = SCOPE_DEFER_NORMAL or SCOPE_DEFER_ERROR
    Scope* parent;
    uint32_t index;
    uint32_t len;
} ScopeDefer;

// Scope.Label — for labeled blocks and loops.
typedef struct {
    Scope base; // tag = SCOPE_LABEL
    Scope* parent;
    uint32_t label_name; // NullTerminatedString
    uint32_t block_inst; // instruction index (not ref)
} ScopeLabel;

// Scope.Namespace (AstGen.zig:11737-11762) — represents a type declaration
// scope (struct, enum, union, opaque) that has declarations in it.
typedef struct {
    Scope base; // tag = SCOPE_NAMESPACE
    Scope* parent;
    uint32_t node; // AST node of the container decl
    uint32_t inst; // instruction index of the container decl
    GenZir* declaring_gz; // the GenZir containing this namespace
    bool maybe_generic; // true if inside a function (astgen.within_fn)
    // Per-namespace declaration table (maps name string index → node index).
    uint32_t* decl_names;
    uint32_t* decl_nodes;
    uint32_t decl_len;
    uint32_t decl_cap;
    // Captures (populated by tunnelThroughClosure).
    // Keys are packed Capture u32 values, values are NullTerminatedString.
    uint32_t* capture_keys;
    uint32_t* capture_vals;
    uint32_t captures_len;
    uint32_t captures_cap;
} ScopeNamespace;

// Initialize a ScopeNamespace on the stack.
static void scopeNamespaceInit(ScopeNamespace* ns, Scope* parent,
    uint32_t node, uint32_t inst, GenZir* declaring_gz, bool maybe_generic) {
    memset(ns, 0, sizeof(*ns));
    ns->base.tag = SCOPE_NAMESPACE;
    ns->parent = parent;
    ns->node = node;
    ns->inst = inst;
    ns->declaring_gz = declaring_gz;
    ns->maybe_generic = maybe_generic;
}

// Free dynamic arrays in a ScopeNamespace.
static void scopeNamespaceDeinit(ScopeNamespace* ns) {
    free(ns->decl_names);
    free(ns->decl_nodes);
    free(ns->capture_keys);
    free(ns->capture_vals);
}

// Add a declaration to a namespace's decl table.
static void scopeNamespaceAddDecl(
    ScopeNamespace* ns, uint32_t name_str, uint32_t decl_node) {
    if (ns->decl_len >= ns->decl_cap) {
        uint32_t new_cap = ns->decl_cap > 0 ? ns->decl_cap * 2 : 8;
        uint32_t* n = realloc(ns->decl_names, new_cap * sizeof(uint32_t));
        uint32_t* d = realloc(ns->decl_nodes, new_cap * sizeof(uint32_t));
        if (!n || !d)
            exit(1);
        ns->decl_names = n;
        ns->decl_nodes = d;
        ns->decl_cap = new_cap;
    }
    ns->decl_names[ns->decl_len] = name_str;
    ns->decl_nodes[ns->decl_len] = decl_node;
    ns->decl_len++;
}

// Look up a name in a namespace's decl table. Returns the node index,
// or UINT32_MAX if not found.
static uint32_t scopeNamespaceFindDecl(
    const ScopeNamespace* ns, uint32_t name_str) {
    for (uint32_t i = 0; i < ns->decl_len; i++) {
        if (ns->decl_names[i] == name_str)
            return ns->decl_nodes[i];
    }
    return UINT32_MAX;
}

// Add a capture to a namespace. Returns the capture index (position).
// If the capture already exists, returns the existing index.
// key is a packed Capture u32 (3-bit tag | 29-bit data).
static uint32_t scopeNamespaceAddCapture(
    ScopeNamespace* ns, uint32_t key, uint32_t name_str) {
    // Check for existing capture with same key.
    for (uint32_t i = 0; i < ns->captures_len; i++) {
        if (ns->capture_keys[i] == key)
            return i;
    }
    if (ns->captures_len >= ns->captures_cap) {
        uint32_t new_cap = ns->captures_cap > 0 ? ns->captures_cap * 2 : 4;
        uint32_t* k = realloc(ns->capture_keys, new_cap * sizeof(uint32_t));
        uint32_t* v = realloc(ns->capture_vals, new_cap * sizeof(uint32_t));
        if (!k || !v)
            exit(1);
        ns->capture_keys = k;
        ns->capture_vals = v;
        ns->captures_cap = new_cap;
    }
    uint32_t idx = ns->captures_len;
    ns->capture_keys[idx] = key;
    ns->capture_vals[idx] = name_str;
    ns->captures_len++;
    return idx;
}

// Walk to a scope's parent. Returns NULL if there is no parent.
static Scope* scopeParent(Scope* s) {
    switch (s->tag) {
    case SCOPE_GEN_ZIR:
        return ((GenZir*)s)->parent;
    case SCOPE_LOCAL_VAL:
        return ((ScopeLocalVal*)s)->parent;
    case SCOPE_LOCAL_PTR:
        return ((ScopeLocalPtr*)s)->parent;
    case SCOPE_DEFER_NORMAL:
    case SCOPE_DEFER_ERROR:
        return ((ScopeDefer*)s)->parent;
    case SCOPE_NAMESPACE:
        return ((ScopeNamespace*)s)->parent;
    case SCOPE_LABEL:
        return ((ScopeLabel*)s)->parent;
    case SCOPE_TOP:
        return NULL;
    }
    return NULL;
}

// --- GenZir instruction helpers (AstGen.zig:11830-11850) ---

// Returns the number of instructions in this scope.
static uint32_t gzInstructionsLen(const GenZir* gz) {
    return gz->astgen->scratch_inst_len - gz->instructions_top;
}

// Returns pointer to start of this scope's instructions in the shared array.
static const uint32_t* gzInstructionsSlice(const GenZir* gz) {
    return gz->astgen->scratch_instructions + gz->instructions_top;
}

// Mirrors GenZir.instructionsSliceUpto (AstGen.zig:11835).
// Returns instructions from gz up to (but not including) stacked_gz's start.
static uint32_t gzInstructionsLenUpto(
    const GenZir* gz, const GenZir* stacked_gz) {
    return stacked_gz->instructions_top - gz->instructions_top;
}

static const uint32_t* gzInstructionsSliceUpto(
    const GenZir* gz, const GenZir* stacked_gz) {
    (void)stacked_gz; // used only for length computation
    return gz->astgen->scratch_instructions + gz->instructions_top;
}

// Mirrors GenZir.unstack (AstGen.zig:11822).
// Restores the shared array length to this scope's start.
static void gzUnstack(GenZir* gz) {
    gz->astgen->scratch_inst_len = gz->instructions_top;
}

// Append an instruction index to this scope's portion of the shared array.
static void gzAppendInstruction(GenZir* gz, uint32_t inst_idx) {
    AstGenCtx* ag = gz->astgen;
    if (ag->scratch_inst_len >= ag->scratch_inst_cap) {
        uint32_t new_cap
            = ag->scratch_inst_cap > 0 ? ag->scratch_inst_cap * 2 : 64;
        uint32_t* p
            = realloc(ag->scratch_instructions, new_cap * sizeof(uint32_t));
        if (!p)
            exit(1);
        ag->scratch_instructions = p;
        ag->scratch_inst_cap = new_cap;
    }
    ag->scratch_instructions[ag->scratch_inst_len++] = inst_idx;
}

// Mirrors GenZir.makeSubBlock (AstGen.zig:11852).
static GenZir makeSubBlock(GenZir* parent, Scope* scope) {
    GenZir sub;
    memset(&sub, 0, sizeof(sub));
    sub.base.tag = SCOPE_GEN_ZIR;
    sub.parent = scope;
    sub.astgen = parent->astgen;
    sub.decl_node_index = parent->decl_node_index;
    sub.decl_line = parent->decl_line;
    sub.is_comptime = parent->is_comptime;
    sub.c_import = parent->c_import;
    sub.is_typeof = parent->is_typeof;
    sub.instructions_top = parent->astgen->scratch_inst_len;
    sub.break_block = UINT32_MAX;
    sub.continue_block = UINT32_MAX;
    sub.label_token = UINT32_MAX;
    sub.any_defer_node = parent->any_defer_node;
    return sub;
}

// --- Capacity helpers ---

static void ensureExtraCapacity(AstGenCtx* ag, uint32_t additional) {
    uint32_t needed = ag->extra_len + additional;
    if (needed > ag->extra_cap) {
        uint32_t new_cap = ag->extra_cap * 2;
        if (new_cap < needed)
            new_cap = needed;
        uint32_t* p = realloc(ag->extra, new_cap * sizeof(uint32_t));
        if (!p)
            exit(1);
        ag->extra = p;
        ag->extra_cap = new_cap;
    }
}

static void ensureInstCapacity(AstGenCtx* ag, uint32_t additional) {
    uint32_t needed = ag->inst_len + additional;
    if (needed > ag->inst_cap) {
        uint32_t new_cap = ag->inst_cap * 2;
        if (new_cap < needed)
            new_cap = needed;
        ZirInstTag* t = realloc(ag->inst_tags, new_cap * sizeof(ZirInstTag));
        ZirInstData* d
            = realloc(ag->inst_datas, new_cap * sizeof(ZirInstData));
        if (!t || !d)
            exit(1);
        ag->inst_tags = t;
        ag->inst_datas = d;
        ag->inst_cap = new_cap;
    }
}

static void ensureStringBytesCapacity(AstGenCtx* ag, uint32_t additional) {
    uint32_t needed = ag->string_bytes_len + additional;
    if (needed > ag->string_bytes_cap) {
        uint32_t new_cap = ag->string_bytes_cap * 2;
        if (new_cap < needed)
            new_cap = needed;
        uint8_t* p = realloc(ag->string_bytes, new_cap * sizeof(uint8_t));
        if (!p)
            exit(1);
        ag->string_bytes = p;
        ag->string_bytes_cap = new_cap;
    }
}

// --- Extra data helpers ---

static uint32_t addExtraU32(AstGenCtx* ag, uint32_t value) {
    ensureExtraCapacity(ag, 1);
    uint32_t idx = ag->extra_len;
    ag->extra[ag->extra_len++] = value;
    return idx;
}

// --- Instruction helpers ---

// Mirrors AstGen.reserveInstructionIndex (AstGen.zig:12902).
static uint32_t reserveInstructionIndex(AstGenCtx* ag) {
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    memset(&ag->inst_datas[idx], 0, sizeof(ZirInstData));
    ag->inst_tags[idx] = (ZirInstTag)0;
    ag->inst_len++;
    return idx;
}

// Forward declarations.
static int32_t tokenIndexToRelative(const GenZir* gz, uint32_t token);
static uint32_t firstToken(const Ast* tree, uint32_t node);
static bool nodesNeedRlContains(const AstGenCtx* ag, uint32_t node);

// Mirrors GenZir.makeUnTok (AstGen.zig:12520).
// Allocates an instruction but does NOT add to GenZir body.
// Returns the raw instruction INDEX (not a Ref).
static uint32_t makeUnTok(
    GenZir* gz, ZirInstTag tag, uint32_t operand, uint32_t abs_tok_index) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ZirInstData data;
    data.un_tok.src_tok = tokenIndexToRelative(gz, abs_tok_index);
    data.un_tok.operand = operand;
    ag->inst_tags[idx] = tag;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    return idx; // Raw index, NOT a Ref.
}

// Mirrors GenZir.add (AstGen.zig:13162).
// Appends an instruction and records it in the GenZir body.
// Returns the instruction index as a Ref (index + ZIR_INST_REF_START_INDEX).
static uint32_t addInstruction(GenZir* gz, ZirInstTag tag, ZirInstData data) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = tag;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    // Record in sub-block body.
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX; // toRef()
}

// Mirrors GenZir.addInt (AstGen.zig:12238).
static uint32_t addInt(GenZir* gz, uint64_t integer) {
    ZirInstData data;
    data.int_val = integer;
    return addInstruction(gz, ZIR_INST_INT, data);
}

// Mirrors GenZir.add for bin data (Zir.zig:1877).
// Creates an instruction with bin data (lhs + rhs stored in inst_datas).
static uint32_t addBin(
    GenZir* gz, ZirInstTag tag, uint32_t lhs, uint32_t rhs) {
    ZirInstData data;
    data.bin.lhs = lhs;
    data.bin.rhs = rhs;
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addPlNode (AstGen.zig:12308).
// Creates an instruction with pl_node data and 2-word payload.
static uint32_t addPlNodeBin(
    GenZir* gz, ZirInstTag tag, uint32_t node, uint32_t lhs, uint32_t rhs) {
    AstGenCtx* ag = gz->astgen;
    ensureExtraCapacity(ag, 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = lhs;
    ag->extra[ag->extra_len++] = rhs;
    ZirInstData data;
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    return addInstruction(gz, tag, data);
}

// Mirrors addPlNode for 3-operand payloads (e.g. ArrayTypeSentinel).
static uint32_t addPlNodeTriple(GenZir* gz, ZirInstTag tag, uint32_t node,
    uint32_t a, uint32_t b, uint32_t c) {
    AstGenCtx* ag = gz->astgen;
    ensureExtraCapacity(ag, 3);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = a;
    ag->extra[ag->extra_len++] = b;
    ag->extra[ag->extra_len++] = c;
    ZirInstData data;
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    return addInstruction(gz, tag, data);
}

// Checks if an AST identifier node is the single underscore `_`.
// Used for inferred array length detection in [_]T patterns.
// Intentionally does NOT support @"_" syntax (matches upstream).
static bool isUnderscoreIdent(const Ast* tree, uint32_t ident_node) {
    uint32_t id_tok = tree->nodes.main_tokens[ident_node];
    uint32_t id_start = tree->tokens.starts[id_tok];
    if (tree->source[id_start] != '_')
        return false;
    if (id_start + 1 >= tree->source_len)
        return true;
    char next = tree->source[id_start + 1];
    return !((next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z')
        || next == '_' || (next >= '0' && next <= '9'));
}

// Mirrors GenZir.addUnNode (AstGen.zig:12406).
static uint32_t addUnNode(
    GenZir* gz, ZirInstTag tag, uint32_t operand, uint32_t node) {
    ZirInstData data;
    data.un_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.un_node.operand = operand;
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addNode (AstGen.zig:12414).
static uint32_t addNode(GenZir* gz, ZirInstTag tag, uint32_t node) {
    ZirInstData data;
    data.node = (int32_t)node - (int32_t)gz->decl_node_index;
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addUnTok (AstGen.zig:12497).
static uint32_t addUnTok(
    GenZir* gz, ZirInstTag tag, uint32_t operand, uint32_t abs_tok_index) {
    ZirInstData data;
    data.un_tok.src_tok = tokenIndexToRelative(gz, abs_tok_index);
    data.un_tok.operand = operand;
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addStrTok (AstGen.zig:12349).
static uint32_t addStrTok(
    GenZir* gz, ZirInstTag tag, uint32_t str_index, uint32_t token) {
    ZirInstData data;
    data.str_tok.start = str_index;
    data.str_tok.src_tok = tokenIndexToRelative(gz, token);
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addPlNodePayloadIndex (AstGen.zig:12332).
static uint32_t addPlNodePayloadIndex(
    GenZir* gz, ZirInstTag tag, uint32_t node, uint32_t payload_index) {
    ZirInstData data;
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    return addInstruction(gz, tag, data);
}

// Mirrors GenZir.addBuiltinValue (AstGen.zig:12389-12391).
// Emits extended instruction with builtin_value opcode.
static uint32_t addBuiltinValue(
    GenZir* gz, uint32_t src_node, uint16_t builtin_val) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    data.extended.opcode = (uint16_t)ZIR_EXT_BUILTIN_VALUE;
    data.extended.small = builtin_val;
    data.extended.operand
        = (uint32_t)((int32_t)src_node - (int32_t)gz->decl_node_index);
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX;
}

// Mirrors GenZir.addNodeExtended (AstGen.zig:12765-12779).
// Creates an extended instruction with operand = node offset.
static uint32_t addNodeExtended(
    GenZir* gz, uint16_t opcode, uint32_t src_node) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    data.extended.opcode = opcode;
    data.extended.small = 0;
    data.extended.operand
        = (uint32_t)((int32_t)src_node - (int32_t)gz->decl_node_index);
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX;
}

// Mirrors GenZir.addExtendedNodeSmall (AstGen.zig:12479-12499).
// Creates an extended instruction with operand = node offset and custom small.
static uint32_t addNodeExtendedSmall(
    GenZir* gz, uint16_t opcode, uint32_t src_node, uint16_t small) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    data.extended.opcode = opcode;
    data.extended.small = small;
    data.extended.operand
        = (uint32_t)((int32_t)src_node - (int32_t)gz->decl_node_index);
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX;
}

// Mirrors GenZir.addExtendedPayload (AstGen.zig:12781).
// Creates an extended instruction with given payload_index and small=0.
static uint32_t addExtendedPayload(
    GenZir* gz, uint16_t opcode, uint32_t payload_index) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    data.extended.opcode = opcode;
    data.extended.small = 0;
    data.extended.operand = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX;
}

// Mirrors GenZir.addExtendedPayloadSmall (variant with small field).
// Creates an extended instruction with given payload_index and small value.
static uint32_t addExtendedPayloadSmall(
    GenZir* gz, uint16_t opcode, uint16_t small, uint32_t payload_index) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    data.extended.opcode = opcode;
    data.extended.small = small;
    data.extended.operand = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx + ZIR_REF_START_INDEX;
}

// --- Source cursor (AstGen.zig:13335-13359) ---

// Mirrors AstGen.advanceSourceCursor (AstGen.zig:13342).
static void advanceSourceCursor(AstGenCtx* ag, uint32_t end) {
    const char* source = ag->tree->source;
    uint32_t i = ag->source_offset;
    uint32_t line = ag->source_line;
    uint32_t column = ag->source_column;
    assert(i <= end);
    while (i < end) {
        if (source[i] == '\n') {
            line++;
            column = 0;
        } else {
            column++;
        }
        i++;
    }
    ag->source_offset = i;
    ag->source_line = line;
    ag->source_column = column;
}

// Mirrors tree.firstToken (Ast.zig:596).
// Recurse through nodes to find the first token.
static uint32_t firstToken(const Ast* tree, uint32_t node) {
    uint32_t end_offset = 0;
    uint32_t n = node;
    while (1) {
        AstNodeTag tag = tree->nodes.tags[n];
        switch (tag) {
        case AST_NODE_ROOT:
            return 0;

        // Return main_token directly (Ast.zig:602-643).
        case AST_NODE_TEST_DECL:
        case AST_NODE_ERRDEFER:
        case AST_NODE_DEFER:
        case AST_NODE_BOOL_NOT:
        case AST_NODE_NEGATION:
        case AST_NODE_BIT_NOT:
        case AST_NODE_NEGATION_WRAP:
        case AST_NODE_ADDRESS_OF:
        case AST_NODE_TRY:
        case AST_NODE_AWAIT:
        case AST_NODE_OPTIONAL_TYPE:
        case AST_NODE_SWITCH:
        case AST_NODE_SWITCH_COMMA:
        case AST_NODE_IF_SIMPLE:
        case AST_NODE_IF:
        case AST_NODE_SUSPEND:
        case AST_NODE_RESUME:
        case AST_NODE_CONTINUE:
        case AST_NODE_BREAK:
        case AST_NODE_RETURN:
        case AST_NODE_ANYFRAME_TYPE:
        case AST_NODE_IDENTIFIER:
        case AST_NODE_ANYFRAME_LITERAL:
        case AST_NODE_CHAR_LITERAL:
        case AST_NODE_NUMBER_LITERAL:
        case AST_NODE_UNREACHABLE_LITERAL:
        case AST_NODE_STRING_LITERAL:
        case AST_NODE_MULTILINE_STRING_LITERAL:
        case AST_NODE_GROUPED_EXPRESSION:
        case AST_NODE_BUILTIN_CALL_TWO:
        case AST_NODE_BUILTIN_CALL_TWO_COMMA:
        case AST_NODE_BUILTIN_CALL:
        case AST_NODE_BUILTIN_CALL_COMMA:
        case AST_NODE_ERROR_SET_DECL:
        case AST_NODE_COMPTIME:
        case AST_NODE_NOSUSPEND:
        case AST_NODE_ASM_SIMPLE:
        case AST_NODE_ASM:
        case AST_NODE_ARRAY_TYPE:
        case AST_NODE_ARRAY_TYPE_SENTINEL:
        case AST_NODE_ERROR_VALUE:
        case AST_NODE_PTR_TYPE_ALIGNED:
        case AST_NODE_PTR_TYPE_SENTINEL:
        case AST_NODE_PTR_TYPE:
        case AST_NODE_PTR_TYPE_BIT_RANGE:
            return tree->nodes.main_tokens[n] - end_offset;

        // Return main_token - 1: dot-prefixed inits and enum_literal
        // (Ast.zig:645-654).
        case AST_NODE_ARRAY_INIT_DOT:
        case AST_NODE_ARRAY_INIT_DOT_COMMA:
        case AST_NODE_ARRAY_INIT_DOT_TWO:
        case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA:
        case AST_NODE_STRUCT_INIT_DOT:
        case AST_NODE_STRUCT_INIT_DOT_COMMA:
        case AST_NODE_STRUCT_INIT_DOT_TWO:
        case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA:
        case AST_NODE_ENUM_LITERAL:
            return tree->nodes.main_tokens[n] - 1 - end_offset;

        // Recurse into LHS: all binary ops and compound expressions
        // (Ast.zig:656-733).
        case AST_NODE_CATCH:
        case AST_NODE_EQUAL_EQUAL:
        case AST_NODE_BANG_EQUAL:
        case AST_NODE_LESS_THAN:
        case AST_NODE_GREATER_THAN:
        case AST_NODE_LESS_OR_EQUAL:
        case AST_NODE_GREATER_OR_EQUAL:
        case AST_NODE_ASSIGN_MUL:
        case AST_NODE_ASSIGN_DIV:
        case AST_NODE_ASSIGN_MOD:
        case AST_NODE_ASSIGN_ADD:
        case AST_NODE_ASSIGN_SUB:
        case AST_NODE_ASSIGN_SHL:
        case AST_NODE_ASSIGN_SHL_SAT:
        case AST_NODE_ASSIGN_SHR:
        case AST_NODE_ASSIGN_BIT_AND:
        case AST_NODE_ASSIGN_BIT_XOR:
        case AST_NODE_ASSIGN_BIT_OR:
        case AST_NODE_ASSIGN_MUL_WRAP:
        case AST_NODE_ASSIGN_ADD_WRAP:
        case AST_NODE_ASSIGN_SUB_WRAP:
        case AST_NODE_ASSIGN_MUL_SAT:
        case AST_NODE_ASSIGN_ADD_SAT:
        case AST_NODE_ASSIGN_SUB_SAT:
        case AST_NODE_ASSIGN:
        case AST_NODE_MERGE_ERROR_SETS:
        case AST_NODE_MUL:
        case AST_NODE_DIV:
        case AST_NODE_MOD:
        case AST_NODE_ARRAY_MULT:
        case AST_NODE_MUL_WRAP:
        case AST_NODE_MUL_SAT:
        case AST_NODE_ADD:
        case AST_NODE_SUB:
        case AST_NODE_ARRAY_CAT:
        case AST_NODE_ADD_WRAP:
        case AST_NODE_SUB_WRAP:
        case AST_NODE_ADD_SAT:
        case AST_NODE_SUB_SAT:
        case AST_NODE_SHL:
        case AST_NODE_SHL_SAT:
        case AST_NODE_SHR:
        case AST_NODE_BIT_AND:
        case AST_NODE_BIT_XOR:
        case AST_NODE_BIT_OR:
        case AST_NODE_ORELSE:
        case AST_NODE_BOOL_AND:
        case AST_NODE_BOOL_OR:
        case AST_NODE_SLICE_OPEN:
        case AST_NODE_ARRAY_ACCESS:
        case AST_NODE_ARRAY_INIT_ONE:
        case AST_NODE_ARRAY_INIT_ONE_COMMA:
        case AST_NODE_SWITCH_RANGE:
        case AST_NODE_ERROR_UNION:
        case AST_NODE_FOR_RANGE:
        case AST_NODE_CALL_ONE:
        case AST_NODE_CALL_ONE_COMMA:
        case AST_NODE_STRUCT_INIT_ONE:
        case AST_NODE_STRUCT_INIT_ONE_COMMA:
        case AST_NODE_CALL:
        case AST_NODE_CALL_COMMA:
        case AST_NODE_STRUCT_INIT:
        case AST_NODE_STRUCT_INIT_COMMA:
        case AST_NODE_SLICE:
        case AST_NODE_SLICE_SENTINEL:
        case AST_NODE_ARRAY_INIT:
        case AST_NODE_ARRAY_INIT_COMMA:
        case AST_NODE_FIELD_ACCESS:
        case AST_NODE_UNWRAP_OPTIONAL:
        case AST_NODE_DEREF:
        case AST_NODE_ASYNC_CALL_ONE:
        case AST_NODE_ASYNC_CALL_ONE_COMMA:
        case AST_NODE_ASYNC_CALL:
        case AST_NODE_ASYNC_CALL_COMMA:
            n = tree->nodes.datas[n].lhs;
            continue;

        // Var decls: scan backwards for modifiers (Ast.zig:771-792).
        case AST_NODE_GLOBAL_VAR_DECL:
        case AST_NODE_LOCAL_VAR_DECL:
        case AST_NODE_SIMPLE_VAR_DECL:
        case AST_NODE_ALIGNED_VAR_DECL: {
            uint32_t mt = tree->nodes.main_tokens[n];
            uint32_t i = mt;
            while (i > 0) {
                TokenizerTag tt = tree->tokens.tags[i - 1];
                if (tt == TOKEN_KEYWORD_EXTERN || tt == TOKEN_KEYWORD_EXPORT
                    || tt == TOKEN_KEYWORD_PUB
                    || tt == TOKEN_KEYWORD_THREADLOCAL
                    || tt == TOKEN_KEYWORD_COMPTIME
                    || tt == TOKEN_STRING_LITERAL) {
                    i--;
                } else {
                    break;
                }
            }
            return i - end_offset;
        }
        // Fn decls: scan backwards for modifiers (Ast.zig:737-759).
        case AST_NODE_FN_DECL:
        case AST_NODE_FN_PROTO_SIMPLE:
        case AST_NODE_FN_PROTO_MULTI:
        case AST_NODE_FN_PROTO_ONE:
        case AST_NODE_FN_PROTO: {
            uint32_t mt = tree->nodes.main_tokens[n];
            uint32_t i = mt;
            while (i > 0) {
                TokenizerTag tt = tree->tokens.tags[i - 1];
                if (tt == TOKEN_KEYWORD_EXTERN || tt == TOKEN_KEYWORD_EXPORT
                    || tt == TOKEN_KEYWORD_PUB || tt == TOKEN_KEYWORD_INLINE
                    || tt == TOKEN_KEYWORD_NOINLINE
                    || tt == TOKEN_STRING_LITERAL) {
                    i--;
                } else {
                    break;
                }
            }
            return i - end_offset;
        }
        // Container fields: check for preceding comptime (Ast.zig:761-769).
        case AST_NODE_CONTAINER_FIELD_INIT:
        case AST_NODE_CONTAINER_FIELD_ALIGN:
        case AST_NODE_CONTAINER_FIELD: {
            uint32_t mt = tree->nodes.main_tokens[n];
            if (mt > 0 && tree->tokens.tags[mt - 1] == TOKEN_KEYWORD_COMPTIME)
                end_offset++;
            return mt - end_offset;
        }
        // Blocks: check for label (Ast.zig:794-805).
        case AST_NODE_BLOCK:
        case AST_NODE_BLOCK_SEMICOLON:
        case AST_NODE_BLOCK_TWO:
        case AST_NODE_BLOCK_TWO_SEMICOLON: {
            uint32_t lbrace = tree->nodes.main_tokens[n];
            if (lbrace >= 2 && tree->tokens.tags[lbrace - 1] == TOKEN_COLON
                && tree->tokens.tags[lbrace - 2] == TOKEN_IDENTIFIER)
                end_offset += 2;
            return lbrace - end_offset;
        }
        // Container decls: check for packed/extern (Ast.zig:807-826).
        case AST_NODE_CONTAINER_DECL:
        case AST_NODE_CONTAINER_DECL_TRAILING:
        case AST_NODE_CONTAINER_DECL_TWO:
        case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
        case AST_NODE_CONTAINER_DECL_ARG:
        case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
        case AST_NODE_TAGGED_UNION:
        case AST_NODE_TAGGED_UNION_TRAILING:
        case AST_NODE_TAGGED_UNION_TWO:
        case AST_NODE_TAGGED_UNION_TWO_TRAILING:
        case AST_NODE_TAGGED_UNION_ENUM_TAG:
        case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING: {
            uint32_t mt = tree->nodes.main_tokens[n];
            if (mt > 0) {
                TokenizerTag prev = tree->tokens.tags[mt - 1];
                if (prev == TOKEN_KEYWORD_PACKED
                    || prev == TOKEN_KEYWORD_EXTERN)
                    end_offset++;
            }
            return mt - end_offset;
        }

        // Switch cases: check for inline/else/values (Ast.zig:834-847).
        case AST_NODE_SWITCH_CASE_ONE:
            if (tree->nodes.datas[n].lhs == 0)
                return tree->nodes.main_tokens[n] - 1 - end_offset;
            n = tree->nodes.datas[n].lhs;
            continue;
        case AST_NODE_SWITCH_CASE_INLINE_ONE:
            if (tree->nodes.datas[n].lhs == 0)
                return tree->nodes.main_tokens[n] - 2;
            end_offset += 1;
            n = tree->nodes.datas[n].lhs;
            continue;
        case AST_NODE_SWITCH_CASE: {
            uint32_t extra_idx = tree->nodes.datas[n].lhs;
            uint32_t items_start = tree->extra_data.arr[extra_idx];
            uint32_t items_end = tree->extra_data.arr[extra_idx + 1];
            if (items_start == items_end)
                return tree->nodes.main_tokens[n] - 1 - end_offset;
            n = tree->extra_data.arr[items_start];
            continue;
        }
        case AST_NODE_SWITCH_CASE_INLINE: {
            uint32_t extra_idx = tree->nodes.datas[n].lhs;
            uint32_t items_start = tree->extra_data.arr[extra_idx];
            uint32_t items_end = tree->extra_data.arr[extra_idx + 1];
            if (items_start == items_end)
                return tree->nodes.main_tokens[n] - 2;
            end_offset += 1;
            n = tree->extra_data.arr[items_start];
            continue;
        }

        // Asm output/input: first token is '[' before main_token
        // (Ast.zig:849-852).
        case AST_NODE_ASM_OUTPUT:
        case AST_NODE_ASM_INPUT:
            return tree->nodes.main_tokens[n] - 1 - end_offset;

        // While/for: check for inline and label (Ast.zig:854-870).
        case AST_NODE_WHILE_SIMPLE:
        case AST_NODE_WHILE_CONT:
        case AST_NODE_WHILE:
        case AST_NODE_FOR_SIMPLE:
        case AST_NODE_FOR: {
            uint32_t result = tree->nodes.main_tokens[n];
            if (result > 0
                && tree->tokens.tags[result - 1] == TOKEN_KEYWORD_INLINE)
                result--;
            if (result >= 2 && tree->tokens.tags[result - 1] == TOKEN_COLON
                && tree->tokens.tags[result - 2] == TOKEN_IDENTIFIER)
                result -= 2;
            return result - end_offset;
        }

        // Assign destructure: recurse into first variable
        // (Ast.zig:735).
        case AST_NODE_ASSIGN_DESTRUCTURE: {
            uint32_t extra_start = tree->nodes.datas[n].lhs;
            // extra_data[extra_start] = variable_count
            // extra_data[extra_start + 1 .. +1+count] = variables
            n = tree->extra_data.arr[extra_start + 1];
            continue;
        }

        // Fallback for any remaining node types.
        default:
            return tree->nodes.main_tokens[n] - end_offset;
        }
    }
}

// Mirrors AstGen.advanceSourceCursorToNode (AstGen.zig:13335).
static void advanceSourceCursorToNode(AstGenCtx* ag, uint32_t node) {
    uint32_t ft = firstToken(ag->tree, node);
    uint32_t token_start = ag->tree->tokens.starts[ft];
    (void)0; // cursor backward check disabled temporarily
    advanceSourceCursor(ag, token_start);
}

// Mirrors maybeAdvanceSourceCursorToMainToken (AstGen.zig:13324).
// Skips advancing when in comptime scope (matching upstream behavior).
static void advanceSourceCursorToMainToken(
    AstGenCtx* ag, const GenZir* gz, uint32_t node) {
    if (gz->is_comptime)
        return;
    uint32_t main_tok = ag->tree->nodes.main_tokens[node];
    uint32_t token_start = ag->tree->tokens.starts[main_tok];
    advanceSourceCursor(ag, token_start);
}

// --- Token helpers ---

// Mirrors GenZir.tokenIndexToRelative (AstGen.zig:11897).
// Returns destination - base as i32.
static int32_t tokenIndexToRelative(const GenZir* gz, uint32_t token) {
    uint32_t base = firstToken(gz->astgen->tree, gz->decl_node_index);
    return (int32_t)token - (int32_t)base;
}

// --- String bytes helpers ---

// Search for an existing null-terminated string in string_bytes.
// Returns the index if found, or UINT32_MAX if not found.
// Mirrors string_table dedup (AstGen.zig:11564).
// Find a string in string_table (registered strings only).
// Mirrors AstGen.string_table hash table lookup.
static uint32_t findExistingString(
    const AstGenCtx* ag, const char* str, uint32_t len) {
    for (uint32_t k = 0; k < ag->string_table_len; k++) {
        uint32_t pos = ag->string_table[k];
        // Compare: string at pos is null-terminated in string_bytes.
        const char* existing = (const char*)ag->string_bytes + pos;
        uint32_t existing_len = (uint32_t)strlen(existing);
        if (existing_len == len && memcmp(existing, str, len) == 0) {
            return pos;
        }
    }
    return UINT32_MAX;
}

// Register a string position in the string table for deduplication.
static void registerString(AstGenCtx* ag, uint32_t pos) {
    if (ag->string_table_len >= ag->string_table_cap) {
        uint32_t new_cap = ag->string_table_cap * 2;
        if (new_cap < 64)
            new_cap = 64;
        uint32_t* p = realloc(ag->string_table, new_cap * sizeof(uint32_t));
        if (!p)
            exit(1);
        ag->string_table = p;
        ag->string_table_cap = new_cap;
    }
    ag->string_table[ag->string_table_len++] = pos;
}

// Mirrors AstGen.tokenIdentEql (AstGen.zig:6148-6152).
// Compares two identifier tokens by source text without touching string_bytes.
static bool tokenIdentEql(const Ast* tree, uint32_t tok1, uint32_t tok2) {
    uint32_t s1 = tree->tokens.starts[tok1];
    uint32_t s2 = tree->tokens.starts[tok2];
    uint32_t e1 = tree->tokens.starts[tok1 + 1];
    uint32_t e2 = tree->tokens.starts[tok2 + 1];
    // Token length includes trailing whitespace in starts delta, but for
    // identifiers the actual content is a contiguous alphanumeric/underscore
    // run. Compute actual identifier lengths.
    uint32_t len1 = 0;
    while (s1 + len1 < e1) {
        char c = tree->source[s1 + len1];
        if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
                || (c >= '0' && c <= '9') || c == '_'))
            break;
        len1++;
    }
    uint32_t len2 = 0;
    while (s2 + len2 < e2) {
        char c = tree->source[s2 + len2];
        if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
                || (c >= '0' && c <= '9') || c == '_'))
            break;
        len2++;
    }
    return len1 == len2
        && memcmp(tree->source + s1, tree->source + s2, len1) == 0;
}

// Forward declaration for strLitAsString (used by identAsString for @"..."
// quoted identifiers with escapes).
static void strLitAsString(AstGenCtx* ag, uint32_t str_lit_token,
    uint32_t* out_index, uint32_t* out_len);

// Mirrors AstGen.identAsString (AstGen.zig:11530).
// Handles both bare identifiers and @"..." quoted identifiers.
static uint32_t identAsString(AstGenCtx* ag, uint32_t ident_token) {
    uint32_t start = ag->tree->tokens.starts[ident_token];
    const char* source = ag->tree->source;

    if (source[start] == '@' && start + 1 < ag->tree->source_len
        && source[start + 1] == '"') {
        // Quoted identifier: @"name" (AstGen.zig:11297-11308).
        // Extract content between quotes, handling escapes.
        uint32_t si, sl;
        // str_lit_token refers to the same token, content starts after @"
        // We reuse strLitAsString but offset by 1 to skip '@'.
        // Actually, strLitAsString expects a token whose source starts
        // with '"'. The @"..." token starts with '@'. We need to handle
        // the offset manually.
        uint32_t content_start = start + 2; // skip @"
        uint32_t content_end = content_start;
        while (
            content_end < ag->tree->source_len && source[content_end] != '"')
            content_end++;
        // Check for escapes.
        bool has_escapes = false;
        for (uint32_t j = content_start; j < content_end; j++) {
            if (source[j] == '\\') {
                has_escapes = true;
                break;
            }
        }

        if (!has_escapes) {
            uint32_t content_len = content_end - content_start;
            uint32_t existing
                = findExistingString(ag, source + content_start, content_len);
            if (existing != UINT32_MAX)
                return existing;
            uint32_t str_index = ag->string_bytes_len;
            ensureStringBytesCapacity(ag, content_len + 1);
            memcpy(ag->string_bytes + ag->string_bytes_len,
                source + content_start, content_len);
            ag->string_bytes_len += content_len;
            ag->string_bytes[ag->string_bytes_len++] = 0;
            registerString(ag, str_index);
            return str_index;
        }

        // With escapes: use strLitAsString-like decoding.
        strLitAsString(ag, ident_token, &si, &sl);
        return si;
    }

    // Bare identifier: scan alphanumeric + underscore.
    uint32_t end = start;
    while (end < ag->tree->source_len) {
        char ch = source[end];
        if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')
            || (ch >= '0' && ch <= '9') || ch == '_') {
            end++;
        } else {
            break;
        }
    }
    uint32_t ident_len = end - start;

    // Check for existing string (dedup).
    uint32_t existing = findExistingString(ag, source + start, ident_len);
    if (existing != UINT32_MAX)
        return existing;

    uint32_t str_index = ag->string_bytes_len;
    ensureStringBytesCapacity(ag, ident_len + 1);
    memcpy(ag->string_bytes + ag->string_bytes_len, source + start, ident_len);
    ag->string_bytes_len += ident_len;
    ag->string_bytes[ag->string_bytes_len++] = 0;
    registerString(ag, str_index);
    return str_index;
}

// Mirrors AstGen.strLitAsString (AstGen.zig:11553).
// Decodes string literal, checks for embedded nulls.
// If embedded null found: store raw bytes without trailing null, no dedup.
// Otherwise: dedup via string_table, add trailing null.
static void strLitAsString(AstGenCtx* ag, uint32_t str_lit_token,
    uint32_t* out_index, uint32_t* out_len) {
    uint32_t tok_start = ag->tree->tokens.starts[str_lit_token];
    const char* source = ag->tree->source;

    // Skip opening quote.
    uint32_t i = tok_start + 1;
    // Find closing quote, skipping escaped characters.
    uint32_t raw_end = i;
    while (raw_end < ag->tree->source_len) {
        if (source[raw_end] == '\\') {
            raw_end += 2; // skip escape + escaped char
        } else if (source[raw_end] == '"') {
            break;
        } else {
            raw_end++;
        }
    }

    // Check if there are any escape sequences.
    bool has_escapes = false;
    for (uint32_t j = i; j < raw_end; j++) {
        if (source[j] == '\\') {
            has_escapes = true;
            break;
        }
    }

    if (!has_escapes) {
        // Fast path: no escapes, no embedded nulls possible.
        uint32_t content_len = raw_end - i;
        uint32_t existing = findExistingString(ag, source + i, content_len);
        if (existing != UINT32_MAX) {
            *out_index = existing;
            *out_len = content_len;
            return;
        }
        uint32_t str_index = ag->string_bytes_len;
        ensureStringBytesCapacity(ag, content_len + 1);
        memcpy(
            ag->string_bytes + ag->string_bytes_len, source + i, content_len);
        ag->string_bytes_len += content_len;
        ag->string_bytes[ag->string_bytes_len++] = 0;
        registerString(ag, str_index);
        *out_index = str_index;
        *out_len = content_len;
        return;
    }

    // Slow path: process escape sequences (AstGen.zig:11558).
    // Decode directly into string_bytes (like upstream).
    uint32_t str_index = ag->string_bytes_len;
    uint32_t max_len = raw_end - i;
    ensureStringBytesCapacity(ag, max_len + 1);
    while (i < raw_end) {
        if (source[i] == '\\') {
            i++;
            if (i >= raw_end)
                break;
            switch (source[i]) {
            case 'n':
                ag->string_bytes[ag->string_bytes_len++] = '\n';
                break;
            case 'r':
                ag->string_bytes[ag->string_bytes_len++] = '\r';
                break;
            case 't':
                ag->string_bytes[ag->string_bytes_len++] = '\t';
                break;
            case '\\':
                ag->string_bytes[ag->string_bytes_len++] = '\\';
                break;
            case '\'':
                ag->string_bytes[ag->string_bytes_len++] = '\'';
                break;
            case '"':
                ag->string_bytes[ag->string_bytes_len++] = '"';
                break;
            case 'x': {
                // \xNN hex escape.
                uint8_t val = 0;
                for (int k = 0; k < 2 && i + 1 < raw_end; k++) {
                    i++;
                    char c = source[i];
                    if (c >= '0' && c <= '9')
                        val = (uint8_t)(val * 16 + (uint8_t)(c - '0'));
                    else if (c >= 'a' && c <= 'f')
                        val = (uint8_t)(val * 16 + 10 + (uint8_t)(c - 'a'));
                    else if (c >= 'A' && c <= 'F')
                        val = (uint8_t)(val * 16 + 10 + (uint8_t)(c - 'A'));
                }
                ag->string_bytes[ag->string_bytes_len++] = val;
                break;
            }
            case 'u': {
                // \u{NNNNNN} unicode escape (string_literal.zig:194-231).
                // Skip past '{'.
                i++;
                // Parse hex digits until '}'.
                uint32_t codepoint = 0;
                while (i + 1 < raw_end) {
                    i++;
                    char c = source[i];
                    if (c >= '0' && c <= '9') {
                        codepoint = codepoint * 16 + (uint32_t)(c - '0');
                    } else if (c >= 'a' && c <= 'f') {
                        codepoint = codepoint * 16 + 10 + (uint32_t)(c - 'a');
                    } else if (c >= 'A' && c <= 'F') {
                        codepoint = codepoint * 16 + 10 + (uint32_t)(c - 'A');
                    } else {
                        // Must be '}', done.
                        break;
                    }
                }
                // Encode codepoint as UTF-8 (unicode.zig:53-82).
                if (codepoint <= 0x7F) {
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)codepoint;
                } else if (codepoint <= 0x7FF) {
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0xC0 | (codepoint >> 6));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | (codepoint & 0x3F));
                } else if (codepoint <= 0xFFFF) {
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0xE0 | (codepoint >> 12));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | ((codepoint >> 6) & 0x3F));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | (codepoint & 0x3F));
                } else {
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0xF0 | (codepoint >> 18));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | ((codepoint >> 12) & 0x3F));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | ((codepoint >> 6) & 0x3F));
                    ag->string_bytes[ag->string_bytes_len++]
                        = (uint8_t)(0x80 | (codepoint & 0x3F));
                }
                break;
            }
            default:
                ag->string_bytes[ag->string_bytes_len++] = (uint8_t)source[i];
                break;
            }
        } else {
            ag->string_bytes[ag->string_bytes_len++] = (uint8_t)source[i];
        }
        i++;
    }
    uint32_t decoded_len = ag->string_bytes_len - str_index;
    uint8_t* key = ag->string_bytes + str_index;

    // Check for embedded null bytes (AstGen.zig:11560).
    // If found, skip dedup and don't add trailing null.
    bool has_embedded_null = false;
    for (uint32_t j = 0; j < decoded_len; j++) {
        if (key[j] == 0) {
            has_embedded_null = true;
            break;
        }
    }
    if (has_embedded_null) {
        *out_index = str_index;
        *out_len = decoded_len;
        return;
    }

    // Dedup against string_table (AstGen.zig:11564-11585).
    uint32_t existing = findExistingString(ag, (const char*)key, decoded_len);
    if (existing != UINT32_MAX) {
        // Shrink back (AstGen.zig:11570).
        ag->string_bytes_len = str_index;
        *out_index = existing;
        *out_len = decoded_len;
        return;
    }

    // New entry: add trailing null and register.
    ensureStringBytesCapacity(ag, 1);
    ag->string_bytes[ag->string_bytes_len++] = 0;
    registerString(ag, str_index);
    *out_index = str_index;
    *out_len = decoded_len;
}

// --- Declaration helpers ---

// Mirrors GenZir.makeDeclaration (AstGen.zig:12906).
static uint32_t makeDeclaration(AstGenCtx* ag, uint32_t node) {
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_DECLARATION;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.declaration.src_node = node;
    // payload_index is set later by setDeclaration.
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    return idx;
}

// Mirrors GenZir.makeBreakCommon (AstGen.zig:12667).
// Creates a break_inline instruction with a Break payload in extra.
// Records the instruction in the GenZir body.
static uint32_t makeBreakInline(GenZir* gz, uint32_t block_inst,
    uint32_t operand, int32_t operand_src_node) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    ensureExtraCapacity(ag, 2);

    // Write Zir.Inst.Break payload to extra (Zir.zig:2489).
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = (uint32_t)operand_src_node;
    ag->extra[ag->extra_len++] = block_inst;

    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_BREAK_INLINE;
    ZirInstData data;
    data.break_data.operand = operand;
    data.break_data.payload_index = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;

    // Record in sub-block body.
    gzAppendInstruction(gz, idx);
    return idx;
}

// Mirrors GenZir.makeBlockInst (AstGen.zig:12890).
// Creates a pl_node instruction with payload_index left as 0 (set later).
// Does NOT append to gz's instruction list.
// Returns instruction index (not a ref).
static uint32_t makeBlockInst(
    AstGenCtx* ag, ZirInstTag tag, const GenZir* gz, uint32_t node) {
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = tag;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = 0; // set later
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    return idx;
}

// Mirrors appendPossiblyRefdBodyInst (AstGen.zig:13675-13683).
// Appends body_inst first, then recursively appends ref_table entry.
static void appendPossiblyRefdBodyInst(AstGenCtx* ag, uint32_t body_inst) {
    ag->extra[ag->extra_len++] = body_inst;
    uint32_t ref_inst;
    if (refTableFetchRemove(ag, body_inst, &ref_inst)) {
        appendPossiblyRefdBodyInst(ag, ref_inst);
    }
}

// Mirrors appendBodyWithFixupsExtraRefsArrayList (AstGen.zig:13659-13673).
// First processes extra_refs (e.g. param_insts), prepending their ref_table
// entries. Then writes body instructions with ref_table fixups.
static void appendBodyWithFixupsExtraRefs(AstGenCtx* ag, const uint32_t* body,
    uint32_t body_len, const uint32_t* extra_refs, uint32_t extra_refs_len) {
    for (uint32_t i = 0; i < extra_refs_len; i++) {
        uint32_t ref_inst;
        if (refTableFetchRemove(ag, extra_refs[i], &ref_inst)) {
            appendPossiblyRefdBodyInst(ag, ref_inst);
        }
    }
    for (uint32_t i = 0; i < body_len; i++) {
        appendPossiblyRefdBodyInst(ag, body[i]);
    }
}

// Scratch extra capacity helper (for call arg bodies).
static void ensureScratchExtraCapacity(AstGenCtx* ag, uint32_t additional) {
    uint32_t needed = ag->scratch_extra_len + additional;
    if (needed > ag->scratch_extra_cap) {
        uint32_t new_cap = ag->scratch_extra_cap * 2;
        if (new_cap < needed)
            new_cap = needed;
        if (new_cap < 64)
            new_cap = 64;
        uint32_t* p = realloc(ag->scratch_extra, new_cap * sizeof(uint32_t));
        if (!p)
            exit(1);
        ag->scratch_extra = p;
        ag->scratch_extra_cap = new_cap;
    }
}

// Like appendPossiblyRefdBodyInst but appends to scratch_extra instead of
// extra.
static void appendPossiblyRefdBodyInstScratch(
    AstGenCtx* ag, uint32_t body_inst) {
    ag->scratch_extra[ag->scratch_extra_len++] = body_inst;
    uint32_t ref_inst;
    if (refTableFetchRemove(ag, body_inst, &ref_inst)) {
        ensureScratchExtraCapacity(ag, 1);
        appendPossiblyRefdBodyInstScratch(ag, ref_inst);
    }
}

// Mirrors countBodyLenAfterFixupsExtraRefs (AstGen.zig:13694-13711).
static uint32_t countBodyLenAfterFixupsExtraRefs(AstGenCtx* ag,
    const uint32_t* body, uint32_t body_len, const uint32_t* extra_refs,
    uint32_t extra_refs_len) {
    uint32_t count = body_len;
    for (uint32_t i = 0; i < body_len; i++) {
        uint32_t check_inst = body[i];
        const uint32_t* ref;
        while ((ref = refTableGet(ag, check_inst)) != NULL) {
            count++;
            check_inst = *ref;
        }
    }
    for (uint32_t i = 0; i < extra_refs_len; i++) {
        uint32_t check_inst = extra_refs[i];
        const uint32_t* ref;
        while ((ref = refTableGet(ag, check_inst)) != NULL) {
            count++;
            check_inst = *ref;
        }
    }
    return count;
}

// Mirrors countBodyLenAfterFixups (AstGen.zig:13686-13688).
static uint32_t countBodyLenAfterFixups(
    AstGenCtx* ag, const uint32_t* body, uint32_t body_len) {
    return countBodyLenAfterFixupsExtraRefs(ag, body, body_len, NULL, 0);
}

// Mirrors fetchRemoveRefEntries (AstGen.zig:14066-14074).
// For each param_inst, removes its ref_table entry (if present) and saves
// the value. Returns the number of entries removed.
static uint32_t fetchRemoveRefEntries(AstGenCtx* ag,
    const uint32_t* param_insts, uint32_t param_insts_len, uint32_t* result,
    uint32_t result_cap) {
    uint32_t count = 0;
    for (uint32_t i = 0; i < param_insts_len; i++) {
        uint32_t ref_inst;
        if (refTableFetchRemove(ag, param_insts[i], &ref_inst)) {
            if (count < result_cap)
                result[count] = ref_inst;
            count++;
        }
    }
    return count;
}

// Mirrors appendBodyWithFixups (AstGen.zig:13649-13657).
static void appendBodyWithFixups(
    AstGenCtx* ag, const uint32_t* body, uint32_t body_len) {
    for (uint32_t i = 0; i < body_len; i++) {
        appendPossiblyRefdBodyInst(ag, body[i]);
    }
}

// Mirrors GenZir.setBlockBody (AstGen.zig:11949).
// Writes Block payload (body_len + instruction indices) to extra.
// Sets the instruction's payload_index. Unstacks gz.
static void setBlockBody(AstGenCtx* ag, GenZir* gz, uint32_t inst) {
    uint32_t raw_body_len = gzInstructionsLen(gz);
    const uint32_t* body = gzInstructionsSlice(gz);
    uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_body_len);
    ensureExtraCapacity(ag, 1 + body_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = body_len;
    for (uint32_t i = 0; i < raw_body_len; i++) {
        appendPossiblyRefdBodyInst(ag, body[i]);
    }
    ag->inst_datas[inst].pl_node.payload_index = payload_index;
    gzUnstack(gz);
}

// Mirrors GenZir.setTryBody (AstGen.zig:11997).
// Writes Try payload (operand + body_len + instruction indices) to extra.
// Sets the instruction's payload_index. Unstacks gz.
static void setTryBody(
    AstGenCtx* ag, GenZir* gz, uint32_t inst, uint32_t operand) {
    uint32_t raw_body_len = gzInstructionsLen(gz);
    const uint32_t* body = gzInstructionsSlice(gz);
    uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_body_len);
    ensureExtraCapacity(ag, 2 + body_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = operand; // Try.operand
    ag->extra[ag->extra_len++] = body_len; // Try.body_len
    for (uint32_t i = 0; i < raw_body_len; i++) {
        appendPossiblyRefdBodyInst(ag, body[i]);
    }
    ag->inst_datas[inst].pl_node.payload_index = payload_index;
    gzUnstack(gz);
}

// Mirrors GenZir.setBlockComptimeBody (AstGen.zig:11972).
// Like setBlockBody but prepends comptime_reason before body_len.
// Asserts inst is a BLOCK_COMPTIME.
static void setBlockComptimeBody(
    AstGenCtx* ag, GenZir* gz, uint32_t inst, uint32_t comptime_reason) {
    uint32_t raw_body_len = gzInstructionsLen(gz);
    const uint32_t* body = gzInstructionsSlice(gz);
    uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_body_len);
    ensureExtraCapacity(ag, 2 + body_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = comptime_reason;
    ag->extra[ag->extra_len++] = body_len;
    for (uint32_t i = 0; i < raw_body_len; i++) {
        appendPossiblyRefdBodyInst(ag, body[i]);
    }
    ag->inst_datas[inst].pl_node.payload_index = payload_index;
    gzUnstack(gz);
}

// Mirrors GenZir.addBreak (AstGen.zig:12623).
// Creates a ZIR_INST_BREAK instruction.
static uint32_t addBreak(GenZir* gz, ZirInstTag tag, uint32_t block_inst,
    uint32_t operand, int32_t operand_src_node) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    ensureExtraCapacity(ag, 2);

    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = (uint32_t)operand_src_node;
    ag->extra[ag->extra_len++] = block_inst;

    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = tag;
    ZirInstData data;
    data.break_data.operand = operand;
    data.break_data.payload_index = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx;
}

// Mirrors GenZir.addCondBr (AstGen.zig:12834).
// Creates condbr instruction placeholder with src_node set.
// Payload is filled later by setCondBrPayload.
static uint32_t addCondBr(GenZir* gz, ZirInstTag tag, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = tag;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = 0; // set later
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx;
}

// Mirrors setCondBrPayload (AstGen.zig:6501).
// Writes CondBr payload: {condition, then_body_len, else_body_len} then
// then_body instructions, then else_body instructions. Unstacks both scopes.
// IMPORTANT: then_gz and else_gz are stacked (else on top of then), so
// then's instructions must use instructionsSliceUpto(else_gz) to avoid
// including else_gz's instructions in then's body.
static void setCondBrPayload(AstGenCtx* ag, uint32_t condbr_inst,
    uint32_t condition, GenZir* then_gz, GenZir* else_gz) {
    uint32_t raw_then_len = gzInstructionsLenUpto(then_gz, else_gz);
    const uint32_t* then_body = gzInstructionsSliceUpto(then_gz, else_gz);
    uint32_t raw_else_len = gzInstructionsLen(else_gz);
    const uint32_t* else_body = gzInstructionsSlice(else_gz);

    uint32_t then_len = countBodyLenAfterFixups(ag, then_body, raw_then_len);
    uint32_t else_len = countBodyLenAfterFixups(ag, else_body, raw_else_len);

    ensureExtraCapacity(ag, 3 + then_len + else_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = condition; // CondBr.condition
    ag->extra[ag->extra_len++] = then_len; // CondBr.then_body_len
    ag->extra[ag->extra_len++] = else_len; // CondBr.else_body_len
    for (uint32_t i = 0; i < raw_then_len; i++)
        appendPossiblyRefdBodyInst(ag, then_body[i]);
    for (uint32_t i = 0; i < raw_else_len; i++)
        appendPossiblyRefdBodyInst(ag, else_body[i]);

    ag->inst_datas[condbr_inst].pl_node.payload_index = payload_index;
    gzUnstack(else_gz);
    gzUnstack(then_gz);
}

// Does this Declaration.Flags.Id have a name? (Zir.zig:2762)
static bool declIdHasName(DeclFlagsId id) {
    return id != DECL_ID_UNNAMED_TEST && id != DECL_ID_COMPTIME;
}

// Does this Declaration.Flags.Id have a lib name? (Zir.zig:2771)
static bool declIdHasLibName(DeclFlagsId id) {
    switch (id) {
    case DECL_ID_EXTERN_CONST:
    case DECL_ID_PUB_EXTERN_CONST:
    case DECL_ID_EXTERN_VAR:
    case DECL_ID_EXTERN_VAR_THREADLOCAL:
    case DECL_ID_PUB_EXTERN_VAR:
    case DECL_ID_PUB_EXTERN_VAR_THREADLOCAL:
        return true;
    default:
        return false;
    }
}

// Does this Declaration.Flags.Id have a type body? (Zir.zig:2783)
static bool declIdHasTypeBody(DeclFlagsId id) {
    switch (id) {
    case DECL_ID_UNNAMED_TEST:
    case DECL_ID_TEST:
    case DECL_ID_DECLTEST:
    case DECL_ID_COMPTIME:
    case DECL_ID_CONST_SIMPLE:
    case DECL_ID_PUB_CONST_SIMPLE:
    case DECL_ID_VAR_SIMPLE:
    case DECL_ID_PUB_VAR_SIMPLE:
        return false;
    default:
        return true;
    }
}

// Does this Declaration.Flags.Id have a value body? (Zir.zig:2800)
static bool declIdHasValueBody(DeclFlagsId id) {
    switch (id) {
    case DECL_ID_EXTERN_CONST_SIMPLE:
    case DECL_ID_EXTERN_CONST:
    case DECL_ID_PUB_EXTERN_CONST_SIMPLE:
    case DECL_ID_PUB_EXTERN_CONST:
    case DECL_ID_EXTERN_VAR:
    case DECL_ID_EXTERN_VAR_THREADLOCAL:
    case DECL_ID_PUB_EXTERN_VAR:
    case DECL_ID_PUB_EXTERN_VAR_THREADLOCAL:
        return false;
    default:
        return true;
    }
}

// Does this Declaration.Flags.Id have special bodies? (Zir.zig:2815)
static bool declIdHasSpecialBodies(DeclFlagsId id) {
    switch (id) {
    case DECL_ID_UNNAMED_TEST:
    case DECL_ID_TEST:
    case DECL_ID_DECLTEST:
    case DECL_ID_COMPTIME:
    case DECL_ID_CONST_SIMPLE:
    case DECL_ID_CONST_TYPED:
    case DECL_ID_PUB_CONST_SIMPLE:
    case DECL_ID_PUB_CONST_TYPED:
    case DECL_ID_EXTERN_CONST_SIMPLE:
    case DECL_ID_PUB_EXTERN_CONST_SIMPLE:
    case DECL_ID_VAR_SIMPLE:
    case DECL_ID_PUB_VAR_SIMPLE:
        return false;
    default:
        return true;
    }
}

// Mirrors setDeclaration (AstGen.zig:13883).
// Full version with type/align/linksection/addrspace/value bodies.
typedef struct {
    uint32_t src_line;
    uint32_t src_column;
    DeclFlagsId id;
    uint32_t name; // NullTerminatedString index
    uint32_t lib_name; // NullTerminatedString index (UINT32_MAX=none)
    const uint32_t* type_body;
    uint32_t type_body_len;
    const uint32_t* align_body;
    uint32_t align_body_len;
    const uint32_t* linksection_body;
    uint32_t linksection_body_len;
    const uint32_t* addrspace_body;
    uint32_t addrspace_body_len;
    const uint32_t* value_body;
    uint32_t value_body_len;
} SetDeclArgs;

static void setDeclaration(
    AstGenCtx* ag, uint32_t decl_inst, SetDeclArgs args) {
    DeclFlagsId id = args.id;
    bool has_name = declIdHasName(id);
    bool has_lib_name = declIdHasLibName(id);
    bool has_type_body_field = declIdHasTypeBody(id);
    bool has_special_bodies = declIdHasSpecialBodies(id);
    bool has_value_body_field = declIdHasValueBody(id);

    uint32_t type_len
        = countBodyLenAfterFixups(ag, args.type_body, args.type_body_len);
    uint32_t align_len
        = countBodyLenAfterFixups(ag, args.align_body, args.align_body_len);
    uint32_t linksection_len = countBodyLenAfterFixups(
        ag, args.linksection_body, args.linksection_body_len);
    uint32_t addrspace_len = countBodyLenAfterFixups(
        ag, args.addrspace_body, args.addrspace_body_len);
    uint32_t value_len
        = countBodyLenAfterFixups(ag, args.value_body, args.value_body_len);

    uint32_t need = 6; // src_hash[4] + flags[2]
    if (has_name)
        need++;
    if (has_lib_name)
        need++;
    if (has_type_body_field)
        need++;
    if (has_special_bodies)
        need += 3;
    if (has_value_body_field)
        need++;
    need += type_len + align_len + linksection_len + addrspace_len + value_len;
    ensureExtraCapacity(ag, need);

    uint32_t payload_start = ag->extra_len;

    // src_hash (4 words): zero-filled; hash comparison skipped in tests.
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;

    // Declaration.Flags: packed struct(u64) { src_line: u30, src_column: u29,
    // id: u5 } (Zir.zig:2719)
    uint64_t flags = 0;
    flags |= (uint64_t)(args.src_line & 0x3FFFFFFFu);
    flags |= (uint64_t)(args.src_column & 0x1FFFFFFFu) << 30;
    flags |= (uint64_t)((uint32_t)id & 0x1Fu) << 59;
    ag->extra[ag->extra_len++] = (uint32_t)(flags & 0xFFFFFFFFu);
    ag->extra[ag->extra_len++] = (uint32_t)(flags >> 32);

    if (has_name)
        ag->extra[ag->extra_len++] = args.name;
    if (has_lib_name) {
        ag->extra[ag->extra_len++]
            = (args.lib_name != UINT32_MAX) ? args.lib_name : 0;
    }
    if (has_type_body_field)
        ag->extra[ag->extra_len++] = type_len;
    if (has_special_bodies) {
        ag->extra[ag->extra_len++] = align_len;
        ag->extra[ag->extra_len++] = linksection_len;
        ag->extra[ag->extra_len++] = addrspace_len;
    }
    if (has_value_body_field)
        ag->extra[ag->extra_len++] = value_len;

    for (uint32_t i = 0; i < args.type_body_len; i++)
        appendPossiblyRefdBodyInst(ag, args.type_body[i]);
    for (uint32_t i = 0; i < args.align_body_len; i++)
        appendPossiblyRefdBodyInst(ag, args.align_body[i]);
    for (uint32_t i = 0; i < args.linksection_body_len; i++)
        appendPossiblyRefdBodyInst(ag, args.linksection_body[i]);
    for (uint32_t i = 0; i < args.addrspace_body_len; i++)
        appendPossiblyRefdBodyInst(ag, args.addrspace_body[i]);
    for (uint32_t i = 0; i < args.value_body_len; i++)
        appendPossiblyRefdBodyInst(ag, args.value_body[i]);

    ag->inst_datas[decl_inst].declaration.payload_index = payload_start;
}

// --- StructDecl.Small packing (Zir.zig StructDecl.Small) ---

typedef struct {
    bool has_captures_len;
    bool has_fields_len;
    bool has_decls_len;
    bool has_backing_int;
    bool known_non_opv;
    bool known_comptime_only;
    uint8_t name_strategy; // 2 bits
    uint8_t layout; // 2 bits
    bool any_default_inits;
    bool any_comptime_fields;
    bool any_aligned_fields;
} StructDeclSmall;

static uint16_t packStructDeclSmall(StructDeclSmall s) {
    uint16_t r = 0;
    if (s.has_captures_len)
        r |= (1u << 0);
    if (s.has_fields_len)
        r |= (1u << 1);
    if (s.has_decls_len)
        r |= (1u << 2);
    if (s.has_backing_int)
        r |= (1u << 3);
    if (s.known_non_opv)
        r |= (1u << 4);
    if (s.known_comptime_only)
        r |= (1u << 5);
    r |= (uint16_t)(s.name_strategy & 0x3u) << 6;
    r |= (uint16_t)(s.layout & 0x3u) << 8;
    if (s.any_default_inits)
        r |= (1u << 10);
    if (s.any_comptime_fields)
        r |= (1u << 11);
    if (s.any_aligned_fields)
        r |= (1u << 12);
    return r;
}

// Mirrors GenZir.setStruct (AstGen.zig:12935).
// Writes StructDecl payload and optional length fields.
// The caller appends captures, backing_int, decls, fields, bodies after.
static void setStruct(AstGenCtx* ag, uint32_t inst, uint32_t src_node,
    StructDeclSmall small, uint32_t captures_len, uint32_t fields_len,
    uint32_t decls_len) {
    ensureExtraCapacity(ag, 6 + 3);

    uint32_t payload_index = ag->extra_len;

    // fields_hash (4 words): zero-filled; hash comparison skipped in tests.
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;

    ag->extra[ag->extra_len++] = ag->source_line;
    ag->extra[ag->extra_len++] = src_node;

    if (small.has_captures_len)
        ag->extra[ag->extra_len++] = captures_len;
    if (small.has_fields_len)
        ag->extra[ag->extra_len++] = fields_len;
    if (small.has_decls_len)
        ag->extra[ag->extra_len++] = decls_len;

    ag->inst_tags[inst] = ZIR_INST_EXTENDED;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.extended.opcode = (uint16_t)ZIR_EXT_STRUCT_DECL;
    data.extended.small = packStructDeclSmall(small);
    data.extended.operand = payload_index;
    ag->inst_datas[inst] = data;
}

// --- scanContainer (AstGen.zig:13384) ---

// Mirrors scanContainer (AstGen.zig:13384).
// Populates the namespace's decl table for identifier resolution.
static uint32_t scanContainer(AstGenCtx* ag, ScopeNamespace* ns,
    const uint32_t* members, uint32_t member_count) {
    const Ast* tree = ag->tree;
    uint32_t decl_count = 0;
    for (uint32_t i = 0; i < member_count; i++) {
        uint32_t member = members[i];
        AstNodeTag tag = tree->nodes.tags[member];
        switch (tag) {
        case AST_NODE_GLOBAL_VAR_DECL:
        case AST_NODE_LOCAL_VAR_DECL:
        case AST_NODE_SIMPLE_VAR_DECL:
        case AST_NODE_ALIGNED_VAR_DECL: {
            decl_count++;
            uint32_t name_token = tree->nodes.main_tokens[member] + 1;
            uint32_t name_str = identAsString(ag, name_token);
            scopeNamespaceAddDecl(ns, name_str, member);
            break;
        }
        case AST_NODE_FN_PROTO_SIMPLE:
        case AST_NODE_FN_PROTO_MULTI:
        case AST_NODE_FN_PROTO_ONE:
        case AST_NODE_FN_PROTO:
        case AST_NODE_FN_DECL: {
            decl_count++;
            uint32_t name_token = tree->nodes.main_tokens[member] + 1;
            uint32_t name_str = identAsString(ag, name_token);
            scopeNamespaceAddDecl(ns, name_str, member);
            break;
        }
        // Container fields: add field name to string table for ordering
        // (AstGen.zig:13509).
        case AST_NODE_CONTAINER_FIELD_INIT:
        case AST_NODE_CONTAINER_FIELD_ALIGN:
        case AST_NODE_CONTAINER_FIELD: {
            uint32_t main_token = tree->nodes.main_tokens[member];
            identAsString(ag, main_token);
            break;
        }
        case AST_NODE_COMPTIME:
            decl_count++;
            break;
        case AST_NODE_TEST_DECL: {
            decl_count++;
            // Process test name string to match upstream string table
            // ordering (AstGen.zig:13465-13500).
            uint32_t test_name_token = tree->nodes.main_tokens[member] + 1;
            TokenizerTag tt = tree->tokens.tags[test_name_token];
            if (tt == TOKEN_STRING_LITERAL) {
                uint32_t si, sl;
                strLitAsString(ag, test_name_token, &si, &sl);
            } else if (tt == TOKEN_IDENTIFIER) {
                identAsString(ag, test_name_token);
            }
            break;
        }
        default:
            break;
        }
    }
    return decl_count;
}

// --- Import tracking ---

static void addImport(AstGenCtx* ag, uint32_t name_index, uint32_t token) {
    // Check for duplicates.
    for (uint32_t i = 0; i < ag->imports_len; i++) {
        if (ag->imports[i].name == name_index)
            return;
    }
    if (ag->imports_len >= ag->imports_cap) {
        uint32_t new_cap = ag->imports_cap > 0 ? ag->imports_cap * 2 : 4;
        ImportEntry* p = realloc(ag->imports, new_cap * sizeof(ImportEntry));
        if (!p)
            exit(1);
        ag->imports = p;
        ag->imports_cap = new_cap;
    }
    ag->imports[ag->imports_len].name = name_index;
    ag->imports[ag->imports_len].token = token;
    ag->imports_len++;
}

// Write imports list to extra (AstGen.zig:227-244).
static void writeImports(AstGenCtx* ag) {
    if (ag->imports_len == 0) {
        ag->extra[ZIR_EXTRA_IMPORTS] = 0;
        return;
    }
    uint32_t need = 1 + ag->imports_len * 2;
    ensureExtraCapacity(ag, need);
    uint32_t imports_index = ag->extra_len;
    ag->extra[ag->extra_len++] = ag->imports_len;
    for (uint32_t i = 0; i < ag->imports_len; i++) {
        ag->extra[ag->extra_len++] = ag->imports[i].name;
        ag->extra[ag->extra_len++] = ag->imports[i].token;
    }
    ag->extra[ZIR_EXTRA_IMPORTS] = imports_index;
}

// ri.br() (AstGen.zig:274-282): convert coerced_ty to ty for branching.
static inline ResultLoc rlBr(ResultLoc rl) {
    if (rl.tag == RL_COERCED_TY) {
        return (ResultLoc) {
            .tag = RL_TY, .data = rl.data, .src_node = 0, .ctx = rl.ctx
        };
    }
    return rl;
}

// setBreakResultInfo (AstGen.zig:11905-11926): compute break result info
// from parent RL. Converts coerced_ty → ty, discard → discard, else passes
// through. For ptr/inferred_ptr, converts to ty/none respectively.
static ResultLoc breakResultInfo(
    GenZir* gz, ResultLoc parent_rl, uint32_t node, bool need_rl) {
    // First: compute block_ri (AstGen.zig:7639-7646).
    // When need_rl is true, forward the rl as-is (don't convert ptr→ty).
    ResultLoc block_ri;
    if (need_rl) {
        block_ri = parent_rl;
    } else {
        switch (parent_rl.tag) {
        case RL_PTR: {
            uint32_t ptr_ty
                = addUnNode(gz, ZIR_INST_TYPEOF, parent_rl.data, node);
            uint32_t ty = addUnNode(gz, ZIR_INST_ELEM_TYPE, ptr_ty, node);
            block_ri = (ResultLoc) {
                .tag = RL_TY, .data = ty, .src_node = 0, .ctx = parent_rl.ctx
            };
            break;
        }
        case RL_INFERRED_PTR:
            block_ri = (ResultLoc) {
                .tag = RL_NONE, .data = 0, .src_node = 0, .ctx = parent_rl.ctx
            };
            break;
        default:
            block_ri = parent_rl;
            break;
        }
    }
    // Then: setBreakResultInfo (AstGen.zig:11910-11925).
    switch (block_ri.tag) {
    case RL_COERCED_TY:
        return (ResultLoc) { .tag = RL_TY,
            .data = block_ri.data,
            .src_node = 0,
            .ctx = block_ri.ctx };
    case RL_DISCARD:
        // Don't forward ctx (AstGen.zig:11916-11920).
        return RL_DISCARD_VAL;
    default:
        return block_ri;
    }
}

// resultType (AstGen.zig:341-351): extract result type from RL.
// Returns 0 if no result type available.
static uint32_t rlResultType(GenZir* gz, ResultLoc rl, uint32_t node) {
    switch (rl.tag) {
    case RL_TY:
    case RL_COERCED_TY:
        return rl.data;
    case RL_REF_COERCED_TY:
        // AstGen.zig:345: .ref_coerced_ty => |ptr_ty| gz.addUnNode(.elem_type,
        // ptr_ty, node)
        return addUnNode(gz, ZIR_INST_ELEM_TYPE, rl.data, node);
    case RL_PTR: {
        // typeof(ptr) -> elem_type (AstGen.zig:346-349).
        uint32_t ptr_ty = addUnNode(gz, ZIR_INST_TYPEOF, rl.data, node);
        return addUnNode(gz, ZIR_INST_ELEM_TYPE, ptr_ty, node);
    }
    default:
        return 0;
    }
}

// Mirrors ResultLoc.resultTypeForCast (AstGen.zig:356-368).
// Like rlResultType but errors if no result type is available.
static uint32_t rlResultTypeForCast(GenZir* gz, ResultLoc rl, uint32_t node) {
    uint32_t ty = rlResultType(gz, rl, node);
    if (ty != 0)
        return ty;
    SET_ERROR(gz->astgen);
    return 0;
}

static bool endsWithNoReturn(GenZir* gz);

// Mirrors Zir.Inst.Tag.isAlwaysVoid (Zir.zig:1343-1608).
static bool isAlwaysVoid(ZirInstTag tag, ZirInstData data) {
    switch (tag) {
    case ZIR_INST_DBG_STMT:
    case ZIR_INST_DBG_VAR_PTR:
    case ZIR_INST_DBG_VAR_VAL:
    case ZIR_INST_ENSURE_RESULT_USED:
    case ZIR_INST_ENSURE_RESULT_NON_ERROR:
    case ZIR_INST_ENSURE_ERR_UNION_PAYLOAD_VOID:
    case ZIR_INST_SET_EVAL_BRANCH_QUOTA:
    case ZIR_INST_ATOMIC_STORE:
    case ZIR_INST_STORE_NODE:
    case ZIR_INST_STORE_TO_INFERRED_PTR:
    case ZIR_INST_VALIDATE_DEREF:
    case ZIR_INST_VALIDATE_DESTRUCTURE:
    case ZIR_INST_EXPORT:
    case ZIR_INST_SET_RUNTIME_SAFETY:
    case ZIR_INST_MEMCPY:
    case ZIR_INST_MEMSET:
    case ZIR_INST_MEMMOVE:
    case ZIR_INST_CHECK_COMPTIME_CONTROL_FLOW:
    case ZIR_INST_DEFER:
    case ZIR_INST_DEFER_ERR_CODE:
    case ZIR_INST_SAVE_ERR_RET_INDEX:
    case ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL:
    case ZIR_INST_RESTORE_ERR_RET_INDEX_FN_ENTRY:
    case ZIR_INST_VALIDATE_STRUCT_INIT_TY:
    case ZIR_INST_VALIDATE_STRUCT_INIT_RESULT_TY:
    case ZIR_INST_VALIDATE_PTR_STRUCT_INIT:
    case ZIR_INST_VALIDATE_ARRAY_INIT_TY:
    case ZIR_INST_VALIDATE_ARRAY_INIT_RESULT_TY:
    case ZIR_INST_VALIDATE_PTR_ARRAY_INIT:
    case ZIR_INST_VALIDATE_REF_TY:
    case ZIR_INST_VALIDATE_CONST:
        return true;
    case ZIR_INST_EXTENDED:
        switch (data.extended.opcode) {
        case ZIR_EXT_BRANCH_HINT:
        case ZIR_EXT_BREAKPOINT:
        case ZIR_EXT_DISABLE_INSTRUMENTATION:
        case ZIR_EXT_DISABLE_INTRINSICS:
            return true;
        default:
            return false;
        }
    default:
        return false;
    }
}

// rvalue (AstGen.zig:11051-11224): apply result location wrapping.
static uint32_t rvalue(
    GenZir* gz, ResultLoc rl, uint32_t result, uint32_t node) {
    // isAlwaysVoid check (AstGen.zig:11058-11067).
    if (result >= ZIR_REF_START_INDEX) {
        uint32_t result_index = result - ZIR_REF_START_INDEX;
        if (isAlwaysVoid(gz->astgen->inst_tags[result_index],
                gz->astgen->inst_datas[result_index])) {
            result = ZIR_REF_VOID_VALUE;
        }
    }
    // endsWithNoReturn check (AstGen.zig:11068).
    if (endsWithNoReturn(gz))
        return result;
    switch (rl.tag) {
    case RL_NONE:
    case RL_COERCED_TY:
        return result;
    case RL_DISCARD:
        // ensure_result_non_error (AstGen.zig:11071-11074).
        addUnNode(gz, ZIR_INST_ENSURE_RESULT_NON_ERROR, result, node);
        return ZIR_REF_VOID_VALUE;
    case RL_REF:
    case RL_REF_COERCED_TY: {
        // coerce_ptr_elem_ty for ref_coerced_ty (AstGen.zig:11077-11083).
        uint32_t coerced_result = result;
        if (rl.tag == RL_REF_COERCED_TY) {
            coerced_result = addPlNodeBin(
                gz, ZIR_INST_COERCE_PTR_ELEM_TY, node, rl.data, result);
        }
        AstGenCtx* ag = gz->astgen;
        uint32_t src_token = firstToken(ag->tree, node);
        // If result is not an instruction index (e.g. a well-known ref),
        // emit ref directly (AstGen.zig:11091-11092).
        if (coerced_result < ZIR_REF_START_INDEX) {
            return addUnTok(gz, ZIR_INST_REF, coerced_result, src_token);
        }
        // Deduplication via ref_table (AstGen.zig:11093-11097).
        uint32_t result_index = coerced_result - ZIR_REF_START_INDEX;
        bool found;
        uint32_t* val_ptr = refTableGetOrPut(ag, result_index, &found);
        if (!found) {
            *val_ptr = makeUnTok(gz, ZIR_INST_REF, coerced_result, src_token);
        }
        return *val_ptr + ZIR_REF_START_INDEX;
    }
    case RL_TY: {
        // Quick elimination of common, unnecessary type coercions
        // (AstGen.zig:11099-11209).
#define RC(t, v) (((uint64_t)(t) << 32) | (uint64_t)(v))
        uint64_t combined = RC(rl.data, result);
        switch (combined) {
        // Identity: type of result is already correct
        // (AstGen.zig:11109-11176).
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U1_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U8_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_I8_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U16_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U29_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_I16_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U32_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_I32_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U64_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_I64_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_U128_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_I128_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_USIZE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ISIZE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_CHAR_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_SHORT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_USHORT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_INT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_UINT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_LONG_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_ULONG_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_LONGLONG_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_ULONGLONG_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_C_LONGDOUBLE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_F16_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_F32_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_F64_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_F80_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_F128_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ANYOPAQUE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_BOOL_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_VOID_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_TYPE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ANYERROR_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_COMPTIME_INT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_COMPTIME_FLOAT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_NORETURN_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ANYFRAME_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_NULL_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_UNDEFINED_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ENUM_LITERAL_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_PTR_USIZE_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_PTR_CONST_COMPTIME_INT_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_MANYPTR_U8_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_MANYPTR_CONST_U8_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_MANYPTR_CONST_U8_SENTINEL_0_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_SLICE_CONST_U8_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_SLICE_CONST_U8_SENTINEL_0_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_ANYERROR_VOID_ERROR_UNION_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_GENERIC_POISON_TYPE):
        case RC(ZIR_REF_TYPE_TYPE, ZIR_REF_EMPTY_TUPLE_TYPE):
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ZERO):
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ONE):
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_NEGATIVE_ONE):
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_UNDEF_USIZE):
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ZERO_USIZE):
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ONE_USIZE):
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_UNDEF_U1):
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ZERO_U1):
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ONE_U1):
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ZERO_U8):
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ONE_U8):
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_FOUR_U8):
        case RC(ZIR_REF_BOOL_TYPE, ZIR_REF_UNDEF_BOOL):
        case RC(ZIR_REF_BOOL_TYPE, ZIR_REF_BOOL_TRUE):
        case RC(ZIR_REF_BOOL_TYPE, ZIR_REF_BOOL_FALSE):
        case RC(ZIR_REF_VOID_TYPE, ZIR_REF_VOID_VALUE):
            return result;
        // Conversions (AstGen.zig:11178-11202).
        case RC(ZIR_REF_BOOL_TYPE, ZIR_REF_UNDEF):
            return ZIR_REF_UNDEF_BOOL;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_UNDEF):
            return ZIR_REF_UNDEF_USIZE;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_UNDEF_U1):
            return ZIR_REF_UNDEF_USIZE;
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_UNDEF):
            return ZIR_REF_UNDEF_U1;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ZERO):
            return ZIR_REF_ZERO_USIZE;
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ZERO):
            return ZIR_REF_ZERO_U1;
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ZERO):
            return ZIR_REF_ZERO_U8;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ONE):
            return ZIR_REF_ONE_USIZE;
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ONE):
            return ZIR_REF_ONE_U1;
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ONE):
            return ZIR_REF_ONE_U8;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ZERO_USIZE):
            return ZIR_REF_ZERO;
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ZERO_USIZE):
            return ZIR_REF_ZERO_U1;
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ZERO_USIZE):
            return ZIR_REF_ZERO_U8;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ONE_USIZE):
            return ZIR_REF_ONE;
        case RC(ZIR_REF_U1_TYPE, ZIR_REF_ONE_USIZE):
            return ZIR_REF_ONE_U1;
        case RC(ZIR_REF_U8_TYPE, ZIR_REF_ONE_USIZE):
            return ZIR_REF_ONE_U8;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ZERO_U1):
            return ZIR_REF_ZERO;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ZERO_U8):
            return ZIR_REF_ZERO;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ZERO_U1):
            return ZIR_REF_ZERO_USIZE;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ZERO_U8):
            return ZIR_REF_ZERO_USIZE;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ONE_U1):
            return ZIR_REF_ONE;
        case RC(ZIR_REF_COMPTIME_INT_TYPE, ZIR_REF_ONE_U8):
            return ZIR_REF_ONE;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ONE_U1):
            return ZIR_REF_ONE_USIZE;
        case RC(ZIR_REF_USIZE_TYPE, ZIR_REF_ONE_U8):
            return ZIR_REF_ONE_USIZE;
        default: {
            ZirInstTag as_tag = (rl.ctx == RI_CTX_SHIFT_OP)
                ? ZIR_INST_AS_SHIFT_OPERAND
                : ZIR_INST_AS_NODE;
            return addPlNodeBin(gz, as_tag, node, rl.data, result);
        }
        }
#undef RC
    }
    case RL_PTR:
        // store_node (AstGen.zig:11211-11216).
        addPlNodeBin(gz, ZIR_INST_STORE_NODE,
            rl.src_node != 0 ? rl.src_node : node, rl.data, result);
        return ZIR_REF_VOID_VALUE;
    case RL_INFERRED_PTR:
        // store_to_inferred_ptr (AstGen.zig:11218-11223).
        addPlNodeBin(
            gz, ZIR_INST_STORE_TO_INFERRED_PTR, node, rl.data, result);
        return ZIR_REF_VOID_VALUE;
    case RL_DESTRUCTURE: {
        // validate_destructure (AstGen.zig:11225-11258).
        uint32_t ds_node = rl.src_node;
        uint32_t comp_len = rl.components_len;
        // Emit validate_destructure: pl_node with ValidateDestructure payload.
        // Payload: { operand, destructure_node (relative), expect_len }
        {
            uint32_t payload_idx = gz->astgen->extra_len;
            ensureExtraCapacity(gz->astgen, 3);
            gz->astgen->extra[gz->astgen->extra_len++] = result; // operand
            gz->astgen->extra[gz->astgen->extra_len++]
                = (uint32_t)((int32_t)ds_node
                    - (int32_t)gz->decl_node_index); // destructure_node
            gz->astgen->extra[gz->astgen->extra_len++]
                = comp_len; // expect_len
            addPlNodePayloadIndex(
                gz, ZIR_INST_VALIDATE_DESTRUCTURE, node, payload_idx);
        }
        for (uint32_t i = 0; i < comp_len; i++) {
            const DestructureComponent* comp = &rl.components[i];
            if (comp->tag == DC_DISCARD)
                continue;
            // elem_val_imm: operand=result, idx=i.
            uint32_t elem_inst = reserveInstructionIndex(gz->astgen);
            gz->astgen->inst_tags[elem_inst] = ZIR_INST_ELEM_VAL_IMM;
            memset(&gz->astgen->inst_datas[elem_inst], 0, sizeof(ZirInstData));
            gz->astgen->inst_datas[elem_inst].elem_val_imm.operand = result;
            gz->astgen->inst_datas[elem_inst].elem_val_imm.idx = i;
            gzAppendInstruction(gz, elem_inst);
            uint32_t elem_ref = elem_inst + ZIR_REF_START_INDEX;
            switch (comp->tag) {
            case DC_TYPED_PTR:
                addPlNodeBin(gz, ZIR_INST_STORE_NODE,
                    comp->src_node != 0 ? comp->src_node : node, comp->inst,
                    elem_ref);
                break;
            case DC_INFERRED_PTR:
                addPlNodeBin(gz, ZIR_INST_STORE_TO_INFERRED_PTR, node,
                    comp->inst, elem_ref);
                break;
            case DC_DISCARD:
                break; // unreachable
            }
        }
        return ZIR_REF_VOID_VALUE;
    }
    }
    return result;
}

// rvalueNoCoercePreRef (AstGen.zig:11042-11049): like rvalue but does NOT
// emit coerce_ptr_elem_ty for RL_REF_COERCED_TY. Used for local var refs.
static uint32_t rvalueNoCoercePreRef(
    GenZir* gz, ResultLoc rl, uint32_t result, uint32_t node) {
    if (rl.tag == RL_REF_COERCED_TY) {
        ResultLoc ref_rl = rl;
        ref_rl.tag = RL_REF;
        return rvalue(gz, ref_rl, result, node);
    }
    return rvalue(gz, rl, result, node);
}

// --- Expression evaluation (AstGen.zig:634) ---

// Forward declarations.
static uint32_t expr(GenZir* gz, Scope* scope, uint32_t node);
// --- DefersToEmit (AstGen.zig:3008) ---
#define DEFER_NORMAL_ONLY 0
#define DEFER_BOTH_SANS_ERR 1

// --- DeferCounts (AstGen.zig:2966) ---
typedef struct {
    bool have_any;
    bool have_normal;
    bool have_err;
    bool need_err_code;
} DeferCounts;
static DeferCounts countDefers(const Scope* outer_scope, Scope* inner_scope);

static uint32_t exprRl(GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static void assignStmt(GenZir* gz, Scope* scope, uint32_t infix_node);
static void assignDestructure(GenZir* gz, Scope* scope, uint32_t node);
static Scope* assignDestructureMaybeDecls(GenZir* gz, Scope* scope,
    uint32_t node, ScopeLocalVal* val_scopes, uint32_t* val_idx,
    ScopeLocalPtr* ptr_scopes, uint32_t* ptr_idx, uint32_t max_scopes);
static void assignOp(
    GenZir* gz, Scope* scope, uint32_t infix_node, ZirInstTag op_tag);
static void assignShift(
    GenZir* gz, Scope* scope, uint32_t infix_node, ZirInstTag op_tag);
static void assignShiftSat(GenZir* gz, Scope* scope, uint32_t infix_node);
static uint32_t shiftOp(
    GenZir* gz, Scope* scope, uint32_t node, ZirInstTag tag);
static void emitDbgStmt(GenZir* gz, uint32_t line, uint32_t column);
static void genDefers(
    GenZir* gz, const Scope* outer_scope, Scope* inner_scope, int which);
static void emitDbgStmtForceCurrentIndex(
    GenZir* gz, uint32_t line, uint32_t column);
static void emitDbgNode(GenZir* gz, uint32_t node);
static void addDbgVar(
    GenZir* gz, ZirInstTag tag, uint32_t name, uint32_t inst);
static bool addEnsureResult(
    GenZir* gz, uint32_t maybe_unused_result, uint32_t statement);
static void blockExprStmts(
    GenZir* gz, Scope* scope, const uint32_t* statements, uint32_t stmt_count);
static uint32_t fullBodyExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static bool nameStratExpr(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint8_t name_strategy, uint32_t* out_ref);
static bool tokenIsUnderscore(const Ast* tree, uint32_t ident_token);
static uint32_t containerDecl(
    GenZir* gz, Scope* scope, uint32_t node, uint8_t name_strategy);
static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint8_t layout,
    uint32_t backing_int_node, uint8_t name_strategy);
static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint8_t layout,
    uint32_t backing_int_node);
static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint32_t arg_node,
    uint8_t name_strategy);
static uint32_t blockExprExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static uint32_t ifExpr(GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static uint32_t forExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, bool is_statement);
static uint32_t orelseCatchExpr(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, ZirInstTag cond_op, ZirInstTag unwrap_op,
    ZirInstTag unwrap_code_op, uint32_t payload_token);
static uint32_t arrayInitDotExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static uint32_t switchExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node);
static uint32_t switchExprErrUnion(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t catch_or_if_node,
    int node_ty); // 0=catch, 1=if
static uint32_t whileExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, bool is_statement);
#define EVAL_TO_ERROR_NEVER 0
#define EVAL_TO_ERROR_ALWAYS 1
#define EVAL_TO_ERROR_MAYBE 2
static int nodeMayEvalToError(const Ast* tree, uint32_t node);
static bool nodeMayAppendToErrorTrace(const Ast* tree, uint32_t node);
static void addSaveErrRetIndex(GenZir* gz, uint32_t operand);
static void addRestoreErrRetIndexBlock(
    GenZir* gz, uint32_t block_inst, uint32_t operand, uint32_t node);
static void restoreErrRetIndex(GenZir* gz, uint32_t block_inst, ResultLoc rl,
    uint32_t node, uint32_t result);
static uint32_t identAsString(AstGenCtx* ag, uint32_t token);
static uint32_t lastToken(const Ast* tree, uint32_t node);
static uint32_t simpleBinOp(
    GenZir* gz, Scope* scope, uint32_t node, ZirInstTag tag);

// Mirrors GenZir.endsWithNoReturn (AstGen.zig:11770).
static bool endsWithNoReturn(GenZir* gz) {
    uint32_t len = gzInstructionsLen(gz);
    if (len == 0)
        return false;
    uint32_t last = gzInstructionsSlice(gz)[len - 1];
    ZirInstTag tag = gz->astgen->inst_tags[last];
    switch (tag) {
    case ZIR_INST_BREAK:
    case ZIR_INST_BREAK_INLINE:
    case ZIR_INST_CONDBR:
    case ZIR_INST_CONDBR_INLINE:
    case ZIR_INST_COMPILE_ERROR:
    case ZIR_INST_RET_NODE:
    case ZIR_INST_RET_LOAD:
    case ZIR_INST_RET_IMPLICIT:
    case ZIR_INST_RET_ERR_VALUE:
    case ZIR_INST_UNREACHABLE:
    case ZIR_INST_REPEAT:
    case ZIR_INST_REPEAT_INLINE:
    case ZIR_INST_PANIC:
    case ZIR_INST_TRAP:
    case ZIR_INST_CHECK_COMPTIME_CONTROL_FLOW:
    case ZIR_INST_SWITCH_CONTINUE:
        return true;
    default:
        return false;
    }
}

// Mirrors GenZir.refIsNoReturn (AstGen.zig:11885).
static bool refIsNoReturn(GenZir* gz, uint32_t inst_ref) {
    if (inst_ref == ZIR_REF_UNREACHABLE_VALUE)
        return true;
    if (inst_ref >= ZIR_REF_START_INDEX) {
        uint32_t inst_index = inst_ref - ZIR_REF_START_INDEX;
        ZirInstTag tag = gz->astgen->inst_tags[inst_index];
        switch (tag) {
        case ZIR_INST_BREAK:
        case ZIR_INST_BREAK_INLINE:
        case ZIR_INST_CONDBR:
        case ZIR_INST_CONDBR_INLINE:
        case ZIR_INST_COMPILE_ERROR:
        case ZIR_INST_RET_NODE:
        case ZIR_INST_RET_LOAD:
        case ZIR_INST_RET_IMPLICIT:
        case ZIR_INST_RET_ERR_VALUE:
        case ZIR_INST_UNREACHABLE:
        case ZIR_INST_REPEAT:
        case ZIR_INST_REPEAT_INLINE:
        case ZIR_INST_PANIC:
        case ZIR_INST_TRAP:
        case ZIR_INST_CHECK_COMPTIME_CONTROL_FLOW:
        case ZIR_INST_SWITCH_CONTINUE:
            return true;
        default:
            return false;
        }
    }
    return false;
}

// Mirrors reachableExpr (AstGen.zig:408-416).
// Wraps exprRl and emits an error if the result is noreturn.
static uint32_t reachableExpr(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint32_t reachable_node) {
    uint32_t result = exprRl(gz, scope, rl, node);
    if (refIsNoReturn(gz, result)) {
        (void)reachable_node;
        SET_ERROR(gz->astgen);
    }
    return result;
}

// Forward declaration needed by reachableExprComptime.
static uint32_t comptimeExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, uint32_t reason);

// Mirrors reachableExprComptime (AstGen.zig:418-438).
// Like reachableExpr but optionally wraps in comptimeExpr when
// comptime_reason is non-zero (i.e. force_comptime is set).
static uint32_t reachableExprComptime(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint32_t reachable_node, uint32_t comptime_reason) {
    uint32_t result;
    if (comptime_reason != 0)
        result = comptimeExpr(gz, scope, rl, node, comptime_reason);
    else
        result = exprRl(gz, scope, rl, node);
    if (refIsNoReturn(gz, result)) {
        (void)reachable_node;
        SET_ERROR(gz->astgen);
    }
    return result;
}

static uint32_t tryResolvePrimitiveIdent(GenZir* gz, uint32_t node);

// SimpleComptimeReason (std.zig:727) — values used in block_comptime payload.
#define COMPTIME_REASON_C_INCLUDE 9
#define COMPTIME_REASON_C_UNDEF 10
#define COMPTIME_REASON_TYPE 29
#define COMPTIME_REASON_ARRAY_SENTINEL 30
#define COMPTIME_REASON_POINTER_SENTINEL 31
#define COMPTIME_REASON_SLICE_SENTINEL 32
#define COMPTIME_REASON_ARRAY_LENGTH 33
#define COMPTIME_REASON_ALIGN 50
#define COMPTIME_REASON_ADDRSPACE 51
#define COMPTIME_REASON_FIELD_NAME 42
#define COMPTIME_REASON_COMPTIME_KEYWORD 53
#define COMPTIME_REASON_ARRAY_MUL_FACTOR 22
#define COMPTIME_REASON_COMPILE_ERROR_STRING 19
#define COMPTIME_REASON_SWITCH_ITEM 56
#define COMPTIME_REASON_TUPLE_FIELD_DEFAULT_VALUE 57
#define COMPTIME_REASON_UNION_FIELD_NAME 45

// Mirrors comptimeExpr2 (AstGen.zig:1982).
// Evaluates a node in a comptime block_comptime scope.
static uint32_t comptimeExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, uint32_t reason) {
    // Skip wrapping when already in comptime context (AstGen.zig:1990).
    if (gz->is_comptime)
        return exprRl(gz, scope, rl, node);
    // Optimization: certain node types are trivially comptime and don't need
    // a block_comptime wrapper (AstGen.zig:1997-2046).
    AstGenCtx* ag = gz->astgen;
    AstNodeTag tag = ag->tree->nodes.tags[node];
    switch (tag) {
    // Identifier handling (AstGen.zig:2000-2003):
    // Upstream calls identifier() with force_comptime which resolves
    // primitives/int types directly and only wraps others in block_comptime.
    // We mirror this by resolving primitives here and falling through for
    // non-primitives.
    case AST_NODE_IDENTIFIER: {
        uint32_t prim = tryResolvePrimitiveIdent(gz, node);
        if (prim != ZIR_REF_NONE)
            return prim;
        break; // non-primitive: fall through to block_comptime wrapping
    }
    case AST_NODE_NUMBER_LITERAL:
    case AST_NODE_CHAR_LITERAL:
    case AST_NODE_STRING_LITERAL:
    case AST_NODE_MULTILINE_STRING_LITERAL:
    case AST_NODE_ENUM_LITERAL:
    case AST_NODE_ERROR_VALUE:
    // Type expressions that force comptime eval of sub-expressions
    // (AstGen.zig:2017-2042).
    case AST_NODE_ERROR_UNION:
    case AST_NODE_MERGE_ERROR_SETS:
    case AST_NODE_OPTIONAL_TYPE:
    case AST_NODE_PTR_TYPE_ALIGNED:
    case AST_NODE_PTR_TYPE_SENTINEL:
    case AST_NODE_PTR_TYPE:
    case AST_NODE_PTR_TYPE_BIT_RANGE:
    case AST_NODE_ARRAY_TYPE:
    case AST_NODE_ARRAY_TYPE_SENTINEL:
    case AST_NODE_FN_PROTO_SIMPLE:
    case AST_NODE_FN_PROTO_MULTI:
    case AST_NODE_FN_PROTO_ONE:
    case AST_NODE_FN_PROTO:
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING:
        return exprRl(gz, scope, rl, node);
    default:
        break;
    }
    // General case: wrap in block_comptime (AstGen.zig:2078-2096).
    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK_COMPTIME, gz, node);
    GenZir block_scope = makeSubBlock(gz, scope);
    block_scope.is_comptime = true;
    // Transform RL to type-only (AstGen.zig:2084-2090).
    ResultLoc ty_only_rl;
    uint32_t res_ty = rlResultType(gz, rl, node);
    if (res_ty != 0)
        ty_only_rl = (ResultLoc) {
            .tag = RL_COERCED_TY, .data = res_ty, .src_node = 0, .ctx = rl.ctx
        };
    else
        ty_only_rl = (ResultLoc) {
            .tag = RL_NONE, .data = 0, .src_node = 0, .ctx = rl.ctx
        };
    uint32_t result = exprRl(&block_scope, scope, ty_only_rl, node);
    addBreak(&block_scope, ZIR_INST_BREAK_INLINE, block_inst, result,
        AST_NODE_OFFSET_NONE);
    setBlockComptimeBody(ag, &block_scope, block_inst, reason);
    gzAppendInstruction(gz, block_inst);
    return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
}

// Mirrors typeExpr (AstGen.zig:394).
static uint32_t typeExpr(GenZir* gz, Scope* scope, uint32_t node) {
    ResultLoc rl = { .tag = RL_COERCED_TY,
        .data = ZIR_REF_TYPE_TYPE,
        .src_node = 0,
        .ctx = RI_CTX_NONE };
    return comptimeExpr(gz, scope, rl, node, COMPTIME_REASON_TYPE);
}

// Sign parameter for numberLiteral (AstGen.zig:8674).
enum NumSign { NUM_SIGN_POSITIVE, NUM_SIGN_NEGATIVE };

// Mirrors numberLiteral (AstGen.zig:8679).
// Parses integer and float literals, returns appropriate ZIR ref.
// source_node is the node used for rvalue/error reporting (may differ from
// node when called from negation).
static uint32_t numberLiteral(
    GenZir* gz, uint32_t node, uint32_t source_node, enum NumSign sign) {
    AstGenCtx* ag = gz->astgen;
    uint32_t num_token = ag->tree->nodes.main_tokens[node];
    uint32_t tok_start = ag->tree->tokens.starts[num_token];
    const char* source = ag->tree->source;

    // Determine token length by scanning to next non-number character.
    uint32_t tok_end = tok_start;
    while (tok_end < ag->tree->source_len
        && ((source[tok_end] >= '0' && source[tok_end] <= '9')
            || source[tok_end] == '_' || source[tok_end] == '.'
            || source[tok_end] == 'x' || source[tok_end] == 'o'
            || source[tok_end] == 'b'
            || (source[tok_end] >= 'a' && source[tok_end] <= 'f')
            || (source[tok_end] >= 'A' && source[tok_end] <= 'F'))) {
        tok_end++;
    }

    // Parse the integer value (simplified: decimal and hex).
    uint64_t value = 0;
    bool is_hex = false;
    uint32_t pos = tok_start;
    if (tok_end - tok_start >= 2 && source[tok_start] == '0'
        && source[tok_start + 1] == 'x') {
        is_hex = true;
        pos = tok_start + 2;
    }

    if (is_hex) {
        for (; pos < tok_end; pos++) {
            if (source[pos] == '_')
                continue;
            if (source[pos] >= '0' && source[pos] <= '9')
                value = value * 16 + (uint64_t)(source[pos] - '0');
            else if (source[pos] >= 'a' && source[pos] <= 'f')
                value = value * 16 + 10 + (uint64_t)(source[pos] - 'a');
            else if (source[pos] >= 'A' && source[pos] <= 'F')
                value = value * 16 + 10 + (uint64_t)(source[pos] - 'A');
        }
    } else {
        for (; pos < tok_end; pos++) {
            if (source[pos] == '_')
                continue;
            if (source[pos] == '.')
                break; // float — not handled yet
            if (source[pos] >= '0' && source[pos] <= '9')
                value = value * 10 + (uint64_t)(source[pos] - '0');
        }
    }

    // Special cases for 0 and 1 (AstGen.zig:8687-8703).
    // Note: upstream errors on negative zero for integers; we return zero
    // regardless of sign to match the same codegen path (AstGen.zig:8687).
    if (value == 0)
        return ZIR_REF_ZERO;
    if (value == 1) {
        return (sign == NUM_SIGN_POSITIVE) ? ZIR_REF_ONE
                                           : ZIR_REF_NEGATIVE_ONE;
    }

    // For other integers, emit the positive value and negate if needed
    // (AstGen.zig:8751-8756).
    uint32_t result = addInt(gz, value);
    if (sign == NUM_SIGN_NEGATIVE) {
        return addUnNode(gz, ZIR_INST_NEGATE, result, source_node);
    }
    return result;
}

// Mirrors builtinCall (AstGen.zig:9191), @import case (AstGen.zig:9242).
static uint32_t builtinCallImport(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    (void)scope;
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    // For builtin_call_two: data.lhs = first arg node.
    AstData node_data = tree->nodes.datas[node];
    uint32_t operand_node = node_data.lhs;

    assert(tree->nodes.tags[operand_node] == AST_NODE_STRING_LITERAL);
    uint32_t str_lit_token = tree->nodes.main_tokens[operand_node];

    uint32_t str_index, str_len;
    strLitAsString(ag, str_lit_token, &str_index, &str_len);

    // Compute res_ty from result location (AstGen.zig:9257).
    uint32_t res_ty_raw = rlResultType(gz, rl, node);
    uint32_t res_ty = (res_ty_raw != 0) ? res_ty_raw : ZIR_REF_NONE;

    // Write Import payload to extra (Zir.Inst.Import: res_ty, path).
    ensureExtraCapacity(ag, 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = res_ty;
    ag->extra[ag->extra_len++] = str_index; // path

    // Create .import instruction with pl_tok data.
    ZirInstData data;
    data.pl_tok.src_tok = tokenIndexToRelative(gz, str_lit_token);
    data.pl_tok.payload_index = payload_index;
    uint32_t result_ref = addInstruction(gz, ZIR_INST_IMPORT, data);

    // Track import (AstGen.zig:9269).
    addImport(ag, str_index, str_lit_token);

    return rvalue(gz, rl, result_ref, node);
}

// Mirrors cImport (AstGen.zig:10011).
static uint32_t cImportExpr(GenZir* gz, Scope* scope, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    AstData nd = ag->tree->nodes.datas[node];
    uint32_t body_node = nd.lhs; // first arg = body

    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_C_IMPORT, gz, node);

    GenZir block_scope = makeSubBlock(gz, scope);
    block_scope.is_comptime = true;
    block_scope.c_import = true;

    // Use fullBodyExpr to inline unlabeled block body (AstGen.zig:10028).
    uint32_t block_result = fullBodyExpr(
        &block_scope, &block_scope.base, RL_NONE_VAL, body_node);

    // ensure_result_used on gz (parent), not block_scope (AstGen.zig:10029).
    addUnNode(gz, ZIR_INST_ENSURE_RESULT_USED, block_result, node);

    // break_inline (AstGen.zig:10030-10032).
    makeBreakInline(
        &block_scope, block_inst, ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);

    setBlockBody(ag, &block_scope, block_inst);
    // block_scope unstacked now, can add to gz.
    gzAppendInstruction(gz, block_inst);

    return block_inst + ZIR_REF_START_INDEX; // toRef()
}

// Mirrors simpleCBuiltin (AstGen.zig:9938).
static uint32_t simpleCBuiltin(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint32_t operand_node, uint16_t ext_tag) {
    AstGenCtx* ag = gz->astgen;

    // Check c_import scope (AstGen.zig:9947).
    if (!gz->c_import) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Evaluate operand as comptimeExpr with coerced_ty=slice_const_u8_type
    // (AstGen.zig:9948-9954).
    uint32_t comptime_reason = (ext_tag == (uint16_t)ZIR_EXT_C_UNDEF)
        ? COMPTIME_REASON_C_UNDEF
        : COMPTIME_REASON_C_INCLUDE;
    ResultLoc operand_rl = { .tag = RL_COERCED_TY,
        .data = ZIR_REF_SLICE_CONST_U8_TYPE,
        .src_node = 0,
        .ctx = RI_CTX_NONE };
    uint32_t operand
        = comptimeExpr(gz, scope, operand_rl, operand_node, comptime_reason);

    // Emit extended instruction with UnNode payload (AstGen.zig:9955).
    ensureExtraCapacity(ag, 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++]
        = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
    ag->extra[ag->extra_len++] = operand;

    ZirInstData data;
    data.extended.opcode = ext_tag;
    data.extended.small = 0xAAAAu; // undefined (addExtendedPayload passes
                                   // undefined for small)
    data.extended.operand = payload_index;
    addInstruction(gz, ZIR_INST_EXTENDED, data);

    return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
}

// Mirrors builtinCall (AstGen.zig:9191) dispatch.
static uint32_t builtinCall(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    uint32_t builtin_token = tree->nodes.main_tokens[node];
    uint32_t tok_start = tree->tokens.starts[builtin_token];
    const char* source = tree->source;

    // Identify builtin name from source.
    // Skip '@' prefix and scan identifier.
    uint32_t name_start = tok_start + 1; // skip '@'
    uint32_t name_end = name_start;
    while (name_end < tree->source_len
        && ((source[name_end] >= 'a' && source[name_end] <= 'z')
            || (source[name_end] >= 'A' && source[name_end] <= 'Z')
            || source[name_end] == '_')) {
        name_end++;
    }
    uint32_t name_len = name_end - name_start;

    // clang-format off
    if (name_len == 6 && memcmp(source + name_start, "import", 6) == 0)
        return builtinCallImport(gz, scope, rl, node);
    if (name_len == 7 && memcmp(source + name_start, "cImport", 7) == 0)
        return cImportExpr(gz, scope, node);
    if (name_len == 8 && memcmp(source + name_start, "cInclude", 8) == 0) {
        AstData nd = tree->nodes.datas[node];
        return simpleCBuiltin(gz, scope, rl, node, nd.lhs, (uint16_t)ZIR_EXT_C_INCLUDE);
    }
    // @intCast — typeCast pattern (AstGen.zig:9416, 9807-9826).
    if (name_len == 7 && memcmp(source + name_start, "intCast", 7) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_INT_CAST, node,
            result_type, operand), node);
    }
    // @embedFile — simpleUnOp with coerced_ty (AstGen.zig:9390).
    if (name_len == 9 && memcmp(source + name_start, "embedFile", 9) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        ResultLoc operand_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE, .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t operand = exprRl(gz, scope, operand_rl, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_EMBED_FILE, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @intFromEnum — simpleUnOp (AstGen.zig:9388).
    if (name_len == 11 && memcmp(source + name_start, "intFromEnum", 11) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_INT_FROM_ENUM, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @tagName — simpleUnOp with dbg_stmt (AstGen.zig:9407).
    if (name_len == 7 && memcmp(source + name_start, "tagName", 7) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        uint32_t result = addUnNode(gz, ZIR_INST_TAG_NAME, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @as (AstGen.zig:8909-8920).
    if (name_len == 2 && memcmp(source + name_start, "as", 2) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t dest_type = typeExpr(gz, scope, nd.lhs);
        ResultLoc as_rl = { .tag = RL_TY, .data = dest_type, .src_node = 0,
            .ctx = rl.ctx };
        uint32_t operand = exprRl(gz, scope, as_rl, nd.rhs);
        return rvalue(gz, rl, operand, node);
    }
    // @truncate — typeCast pattern (AstGen.zig:9417, 9807-9826).
    if (name_len == 8 && memcmp(source + name_start, "truncate", 8) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_TRUNCATE, node,
            result_type, operand), node);
    }
    // @ptrCast — typeCast pattern (AstGen.zig:9056, 9807-9826).
    // TODO: Issue 14 — upstream routes through ptrCast() for nested
    // pointer cast collapsing. Currently uses simple typeCast path.
    if (name_len == 7 && memcmp(source + name_start, "ptrCast", 7) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_PTR_CAST, node,
            result_type, operand), node);
    }
    // @enumFromInt — typeCast pattern (AstGen.zig:9414, 9807-9826).
    if (name_len == 11 && memcmp(source + name_start, "enumFromInt", 11) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_ENUM_FROM_INT, node,
            result_type, operand), node);
    }
    // @bitCast (AstGen.zig:8944-8958, dispatched at 9313).
    if (name_len == 7 && memcmp(source + name_start, "bitCast", 7) == 0) {
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_BITCAST, node,
            result_type, operand), node);
    }
    // @memcpy (AstGen.zig:9631-9637).
    if (name_len == 6 && memcmp(source + name_start, "memcpy", 6) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t dst = expr(gz, scope, nd.lhs);
        uint32_t src = expr(gz, scope, nd.rhs);
        addPlNodeBin(gz, ZIR_INST_MEMCPY, node, dst, src);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    }
    // @memset (AstGen.zig:9638-9647).
    if (name_len == 6 && memcmp(source + name_start, "memset", 6) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t lhs_ty = addUnNode(gz, ZIR_INST_TYPEOF, lhs, nd.lhs);
        uint32_t elem_ty =
            addUnNode(gz, ZIR_INST_INDEXABLE_PTR_ELEM_TYPE, lhs_ty, nd.lhs);
        ResultLoc val_rl = {
            .tag = RL_COERCED_TY, .data = elem_ty, .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t val = exprRl(gz, scope, val_rl, nd.rhs);
        addPlNodeBin(gz, ZIR_INST_MEMSET, node, lhs, val);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    }
    // @min (AstGen.zig:9149-9172).
    if (name_len == 3 && memcmp(source + name_start, "min", 3) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t a = expr(gz, scope, nd.lhs);
        uint32_t b = expr(gz, scope, nd.rhs);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_MIN, node, a, b), node);
    }
    // @max (AstGen.zig:9149-9172).
    if (name_len == 3 && memcmp(source + name_start, "max", 3) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t a = expr(gz, scope, nd.lhs);
        uint32_t b = expr(gz, scope, nd.rhs);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_MAX, node, a, b), node);
    }
    // @panic — simpleUnOp with dbg_node (AstGen.zig:9429-9432).
    if (name_len == 5 && memcmp(source + name_start, "panic", 5) == 0) {
        emitDbgNode(gz, node);
        AstData nd = tree->nodes.datas[node];
        ResultLoc panic_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
            .src_node = 0, .ctx = RI_CTX_NONE };
        uint32_t operand = exprRl(gz, scope, panic_rl, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_PANIC, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @errorName — simpleUnOp with dbg_stmt (AstGen.zig:9391).
    if (name_len == 9 && memcmp(source + name_start, "errorName", 9) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        AstData nd = tree->nodes.datas[node];
        ResultLoc err_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_ANYERROR_TYPE,
            .src_node = 0, .ctx = RI_CTX_NONE };
        uint32_t operand = exprRl(gz, scope, err_rl, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        uint32_t result = addUnNode(gz, ZIR_INST_ERROR_NAME, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @field (AstGen.zig:9288-9300).
    if (name_len == 5 && memcmp(source + name_start, "field", 5) == 0) {
        AstData nd = tree->nodes.datas[node];
        ResultLoc field_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
            .src_node = 0, .ctx = RI_CTX_NONE };
        if (RL_IS_REF(rl)) {
            uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
            uint32_t fname = comptimeExpr(
                gz, scope, field_rl, nd.rhs, COMPTIME_REASON_FIELD_NAME);
            return addPlNodeBin(
                gz, ZIR_INST_FIELD_PTR_NAMED, node, lhs, fname);
        }
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t fname = comptimeExpr(
            gz, scope, field_rl, nd.rhs, COMPTIME_REASON_FIELD_NAME);
        uint32_t result = addPlNodeBin(
            gz, ZIR_INST_FIELD_VAL_NAMED, node, lhs, fname);
        return rvalue(gz, rl, result, node);
    }
    // @sizeOf — simpleUnOpType (AstGen.zig:9381).
    if (name_len == 6 && memcmp(source + name_start, "sizeOf", 6) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = typeExpr(gz, scope, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_SIZE_OF, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @alignOf — simpleUnOpType (AstGen.zig:9383).
    if (name_len == 7 && memcmp(source + name_start, "alignOf", 7) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = typeExpr(gz, scope, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_ALIGN_OF, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @typeInfo — simpleUnOpType (AstGen.zig:9380).
    if (name_len == 8 && memcmp(source + name_start, "typeInfo", 8) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = typeExpr(gz, scope, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_TYPE_INFO, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @compileError — simpleUnOp (AstGen.zig:9386, 9841-9861).
    if (name_len == 12
        && memcmp(source + name_start, "compileError", 12) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        ResultLoc operand_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE, .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t operand = comptimeExpr(gz, scope, operand_rl, nd.lhs,
            COMPTIME_REASON_COMPILE_ERROR_STRING);
        uint32_t result
            = addUnNode(gz, ZIR_INST_COMPILE_ERROR, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @setEvalBranchQuota — simpleUnOp (AstGen.zig:9387, 9841-9861).
    if (name_len == 18
        && memcmp(source + name_start, "setEvalBranchQuota", 18) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        ResultLoc operand_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_U32_TYPE, .src_node = 0, .ctx = RI_CTX_NONE };
        uint32_t operand = exprRl(gz, scope, operand_rl, nd.lhs);
        uint32_t result = addUnNode(
            gz, ZIR_INST_SET_EVAL_BRANCH_QUOTA, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @typeName — simpleUnOp (AstGen.zig:9408, 9841-9861).
    if (name_len == 8 && memcmp(source + name_start, "typeName", 8) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        uint32_t result = addUnNode(gz, ZIR_INST_TYPE_NAME, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @This (AstGen.zig:9371).
    if (name_len == 4 && memcmp(source + name_start, "This", 4) == 0)
        return rvalue(
            gz, rl, addNodeExtended(gz, (uint16_t)ZIR_EXT_THIS, node), node);
    // @memmove (AstGen.zig:9648-9654).
    if (name_len == 7 && memcmp(source + name_start, "memmove", 7) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t dst = expr(gz, scope, nd.lhs);
        uint32_t src_op = expr(gz, scope, nd.rhs);
        addPlNodeBin(gz, ZIR_INST_MEMMOVE, node, dst, src_op);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    }
    // @FieldType (AstGen.zig:9301-9309).
    if (name_len == 9 && memcmp(source + name_start, "FieldType", 9) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t ty_inst = typeExpr(gz, scope, nd.lhs);
        ResultLoc name_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE, .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t name_inst = comptimeExpr(
            gz, scope, name_rl, nd.rhs, COMPTIME_REASON_FIELD_NAME);
        uint32_t result = addPlNodeBin(
            gz, ZIR_INST_FIELD_TYPE_REF, node, ty_inst, name_inst);
        return rvalue(gz, rl, result, node);
    }
    // @reduce (AstGen.zig:9539-9548).
    if (name_len == 6 && memcmp(source + name_start, "reduce", 6) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t reduce_op_ty
            = addBuiltinValue(gz, node, ZIR_BUILTIN_VALUE_REDUCE_OP);
        ResultLoc op_rl = { .tag = RL_COERCED_TY,
            .data = reduce_op_ty, .src_node = 0, .ctx = RI_CTX_NONE };
        uint32_t op = exprRl(gz, scope, op_rl, nd.lhs);
        uint32_t scalar = expr(gz, scope, nd.rhs);
        uint32_t result
            = addPlNodeBin(gz, ZIR_INST_REDUCE, node, op, scalar);
        return rvalue(gz, rl, result, node);
    }
    // @addWithOverflow — overflowArithmetic (AstGen.zig:9550, 10040-10056).
    if (name_len == 15
        && memcmp(source + name_start, "addWithOverflow", 15) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t rhs = expr(gz, scope, nd.rhs);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = rhs;
        uint32_t result = addExtendedPayload(
            gz, (uint16_t)ZIR_EXT_ADD_WITH_OVERFLOW, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @subWithOverflow (AstGen.zig:9551, 10040-10056).
    if (name_len == 15
        && memcmp(source + name_start, "subWithOverflow", 15) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t rhs = expr(gz, scope, nd.rhs);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = rhs;
        uint32_t result = addExtendedPayload(
            gz, (uint16_t)ZIR_EXT_SUB_WITH_OVERFLOW, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @mulWithOverflow (AstGen.zig:9552, 10040-10056).
    if (name_len == 15
        && memcmp(source + name_start, "mulWithOverflow", 15) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t rhs = expr(gz, scope, nd.rhs);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = rhs;
        uint32_t result = addExtendedPayload(
            gz, (uint16_t)ZIR_EXT_MUL_WITH_OVERFLOW, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @shlWithOverflow (AstGen.zig:9553, 10040-10056).
    if (name_len == 15
        && memcmp(source + name_start, "shlWithOverflow", 15) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t lhs = expr(gz, scope, nd.lhs);
        uint32_t rhs = expr(gz, scope, nd.rhs);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = rhs;
        uint32_t result = addExtendedPayload(
            gz, (uint16_t)ZIR_EXT_SHL_WITH_OVERFLOW, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @alignCast — ptrCast family (AstGen.zig:9464-9469, 8969-9087).
    // Simplified: standalone @alignCast uses ptr_cast_full with align_cast flag.
    if (name_len == 9
        && memcmp(source + name_start, "alignCast", 9) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        // align_cast flag = bit 1 (FullPtrCastFlags: ptr_cast=0, align_cast=1)
        uint16_t flags = 0x02;
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = result_type;
        ag->extra[ag->extra_len++] = operand;
        uint32_t result = addExtendedPayloadSmall(
            gz, (uint16_t)ZIR_EXT_PTR_CAST_FULL, flags, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @constCast (AstGen.zig:9464-9469, 8969-9087).
    if (name_len == 9
        && memcmp(source + name_start, "constCast", 9) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        // const_cast flag = bit 3 (FullPtrCastFlags packed u5)
        uint16_t flags = 0x08;
        ensureExtraCapacity(ag, 2);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = operand;
        uint32_t result = addExtendedPayloadSmall(
            gz, (uint16_t)ZIR_EXT_PTR_CAST_NO_DEST, flags, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @volatileCast (AstGen.zig:9464-9469, 8969-9087).
    if (name_len == 12
        && memcmp(source + name_start, "volatileCast", 12) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        // volatile_cast flag = bit 4 (FullPtrCastFlags packed u5)
        uint16_t flags = 0x10;
        ensureExtraCapacity(ag, 2);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = operand;
        uint32_t result = addExtendedPayloadSmall(
            gz, (uint16_t)ZIR_EXT_PTR_CAST_NO_DEST, flags, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @Type (reify) (AstGen.zig:9426-9428, 9747-9781).
    if (name_len == 4 && memcmp(source + name_start, "Type", 4) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t type_info_ty
            = addBuiltinValue(gz, node, ZIR_BUILTIN_VALUE_TYPE_INFO);
        ResultLoc operand_rl = { .tag = RL_COERCED_TY,
            .data = type_info_ty, .src_node = 0, .ctx = RI_CTX_NONE };
        uint32_t operand = exprRl(gz, scope, operand_rl, nd.lhs);
        // Reify payload: absolute node, operand, src_line.
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = node; // absolute node index
        ag->extra[ag->extra_len++] = operand;
        ag->extra[ag->extra_len++] = ag->source_line;
        // name_strat = .anon = 2
        uint32_t result = addExtendedPayloadSmall(
            gz, (uint16_t)ZIR_EXT_REIFY, 2, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // @TypeOf (AstGen.zig:9314, 9089-9147) — single-arg case.
    if (name_len == 6 && memcmp(source + name_start, "TypeOf", 6) == 0) {
        AstData nd = tree->nodes.datas[node];
        uint32_t typeof_inst
            = makeBlockInst(ag, ZIR_INST_TYPEOF_BUILTIN, gz, node);
        GenZir typeof_scope = makeSubBlock(gz, &gz->base);
        typeof_scope.is_comptime = false;
        typeof_scope.is_typeof = true;
        typeof_scope.c_import = false;
        uint32_t ty_expr_ref = reachableExpr(
            &typeof_scope, &typeof_scope.base, RL_NONE_VAL, nd.lhs, node);
        if (!refIsNoReturn(&typeof_scope, ty_expr_ref)) {
            addBreak(&typeof_scope, ZIR_INST_BREAK_INLINE,
                typeof_inst, ty_expr_ref,
                (int32_t)nd.lhs - (int32_t)gz->decl_node_index);
        }
        setBlockBody(ag, &typeof_scope, typeof_inst);
        // typeof_scope unstacked now, add instruction to gz.
        gzAppendInstruction(gz, typeof_inst);
        return rvalue(gz, rl, typeof_inst + ZIR_REF_START_INDEX, node);
    }
    // @intFromPtr — simpleUnOp with dbg_stmt (AstGen.zig:9392).
    if (name_len == 10
        && memcmp(source + name_start, "intFromPtr", 10) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        uint32_t result
            = addUnNode(gz, ZIR_INST_INT_FROM_PTR, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @intFromBool — simpleUnOp (AstGen.zig:9389).
    if (name_len == 11
        && memcmp(source + name_start, "intFromBool", 11) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        uint32_t result
            = addUnNode(gz, ZIR_INST_INT_FROM_BOOL, operand, node);
        return rvalue(gz, rl, result, node);
    }
    // @floatFromInt — typeCast (AstGen.zig:9418, 9807-9826).
    if (name_len == 12
        && memcmp(source + name_start, "floatFromInt", 12) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_FLOAT_FROM_INT,
            node, result_type, operand), node);
    }
    // @intFromFloat — typeCast (AstGen.zig:9419, 9807-9826).
    if (name_len == 12
        && memcmp(source + name_start, "intFromFloat", 12) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_INT_FROM_FLOAT,
            node, result_type, operand), node);
    }
    // @floatCast — typeCast (AstGen.zig:9420, 9807-9826).
    if (name_len == 9
        && memcmp(source + name_start, "floatCast", 9) == 0) {
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_FLOAT_CAST,
            node, result_type, operand), node);
    }
    // @errSetCast — extended error_cast (AstGen.zig:9454-9463).
    if (name_len == 10
        && memcmp(source + name_start, "errSetCast", 10) == 0) {
        emitDbgNode(gz, node);
        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
        AstData nd = tree->nodes.datas[node];
        uint32_t operand = expr(gz, scope, nd.lhs);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++]
            = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
        ag->extra[ag->extra_len++] = result_type;
        ag->extra[ag->extra_len++] = operand;
        uint32_t result = addExtendedPayload(
            gz, (uint16_t)ZIR_EXT_ERROR_CAST, payload_index);
        return rvalue(gz, rl, result, node);
    }
    // clang-format on

    // TODO: handle other builtins.
    SET_ERROR(ag);
    return ZIR_REF_VOID_VALUE;
}

// Mirrors builtinCall for 3+ arg builtins (AST_NODE_BUILTIN_CALL).
// params are in extra_data[params_start..params_end].
static uint32_t builtinCallMultiArg(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint32_t params_start, uint32_t params_end) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    uint32_t builtin_token = tree->nodes.main_tokens[node];
    uint32_t tok_start = tree->tokens.starts[builtin_token];
    const char* source = tree->source;
    uint32_t name_start = tok_start + 1;
    uint32_t name_end = name_start;
    while (name_end < tree->source_len
        && ((source[name_end] >= 'a' && source[name_end] <= 'z')
            || (source[name_end] >= 'A' && source[name_end] <= 'Z')
            || source[name_end] == '_')) {
        name_end++;
    }
    uint32_t name_len = name_end - name_start;
    const uint32_t* params = tree->extra_data.arr + params_start;
    uint32_t param_count = params_end - params_start;

    // @unionInit (AstGen.zig:9315, 8922-8942).
    if (name_len == 9 && memcmp(source + name_start, "unionInit", 9) == 0
        && param_count == 3) {
        uint32_t union_type = typeExpr(gz, scope, params[0]);
        ResultLoc name_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t field_name_ref = comptimeExpr(
            gz, scope, name_rl, params[1], COMPTIME_REASON_UNION_FIELD_NAME);
        // Get field type via field_type_ref.
        uint32_t field_type = addPlNodeBin(
            gz, ZIR_INST_FIELD_TYPE_REF, node, union_type, field_name_ref);
        // Evaluate init value coerced to field type.
        ResultLoc init_rl = {
            .tag = RL_TY, .data = field_type, .src_node = 0, .ctx = rl.ctx
        };
        uint32_t init = reachableExpr(gz, scope, init_rl, params[2], node);
        // Emit union_init: payload = union_type, init, field_name_ref.
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = union_type;
        ag->extra[ag->extra_len++] = init;
        ag->extra[ag->extra_len++] = field_name_ref;
        uint32_t result = addPlNodePayloadIndex(
            gz, ZIR_INST_UNION_INIT, node, payload_index);
        return rvalue(gz, rl, result, node);
    }

    // TODO: handle other multi-arg builtins.
    SET_ERROR(ag);
    return ZIR_REF_VOID_VALUE;
}

// --- identifier (AstGen.zig:8282) ---
// Simplified: handles decl_val resolution for container-level declarations.

// Tries to resolve an identifier as a primitive type or integer type.
// Returns the ZIR ref if it's a primitive/int type, or ZIR_REF_NONE.
// Mirrors primitive_instrs + integer type checks in identifier()
// (AstGen.zig:8298-8337).
static uint32_t tryResolvePrimitiveIdent(GenZir* gz, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    uint32_t ident_token = ag->tree->nodes.main_tokens[node];
    uint32_t tok_start = ag->tree->tokens.starts[ident_token];
    const char* source = ag->tree->source;
    uint32_t tok_end = tok_start;
    while (tok_end < ag->tree->source_len
        && ((source[tok_end] >= 'a' && source[tok_end] <= 'z')
            || (source[tok_end] >= 'A' && source[tok_end] <= 'Z')
            || (source[tok_end] >= '0' && source[tok_end] <= '9')
            || source[tok_end] == '_'))
        tok_end++;
    uint32_t tok_len = tok_end - tok_start;

    // Check well-known primitive refs (primitive_instrs map,
    // AstGen.zig:10236-10281).
    // clang-format off
    if (tok_len == 2 && memcmp(source+tok_start, "u1", 2) == 0) return ZIR_REF_U1_TYPE;
    if (tok_len == 2 && memcmp(source+tok_start, "u8", 2) == 0) return ZIR_REF_U8_TYPE;
    if (tok_len == 2 && memcmp(source+tok_start, "i8", 2) == 0) return ZIR_REF_I8_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "u16", 3) == 0) return ZIR_REF_U16_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "i16", 3) == 0) return ZIR_REF_I16_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "u29", 3) == 0) return ZIR_REF_U29_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "u32", 3) == 0) return ZIR_REF_U32_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "i32", 3) == 0) return ZIR_REF_I32_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "u64", 3) == 0) return ZIR_REF_U64_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "i64", 3) == 0) return ZIR_REF_I64_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "u128", 4) == 0) return ZIR_REF_U128_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "i128", 4) == 0) return ZIR_REF_I128_TYPE;
    if (tok_len == 5 && memcmp(source+tok_start, "usize", 5) == 0) return ZIR_REF_USIZE_TYPE;
    if (tok_len == 5 && memcmp(source+tok_start, "isize", 5) == 0) return ZIR_REF_ISIZE_TYPE;
    if (tok_len == 6 && memcmp(source+tok_start, "c_char", 6) == 0) return ZIR_REF_C_CHAR_TYPE;
    if (tok_len == 7 && memcmp(source+tok_start, "c_short", 7) == 0) return ZIR_REF_C_SHORT_TYPE;
    if (tok_len == 8 && memcmp(source+tok_start, "c_ushort", 8) == 0) return ZIR_REF_C_USHORT_TYPE;
    if (tok_len == 5 && memcmp(source+tok_start, "c_int", 5) == 0) return ZIR_REF_C_INT_TYPE;
    if (tok_len == 6 && memcmp(source+tok_start, "c_uint", 6) == 0) return ZIR_REF_C_UINT_TYPE;
    if (tok_len == 6 && memcmp(source+tok_start, "c_long", 6) == 0) return ZIR_REF_C_LONG_TYPE;
    if (tok_len == 7 && memcmp(source+tok_start, "c_ulong", 7) == 0) return ZIR_REF_C_ULONG_TYPE;
    if (tok_len == 10 && memcmp(source+tok_start, "c_longlong", 10) == 0) return ZIR_REF_C_LONGLONG_TYPE;
    if (tok_len == 11 && memcmp(source+tok_start, "c_ulonglong", 11) == 0) return ZIR_REF_C_ULONGLONG_TYPE;
    if (tok_len == 14 && memcmp(source+tok_start, "comptime_float", 14) == 0) return ZIR_REF_COMPTIME_FLOAT_TYPE;
    if (tok_len == 12 && memcmp(source+tok_start, "comptime_int", 12) == 0) return ZIR_REF_COMPTIME_INT_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "f16", 3) == 0) return ZIR_REF_F16_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "f32", 3) == 0) return ZIR_REF_F32_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "f64", 3) == 0) return ZIR_REF_F64_TYPE;
    if (tok_len == 3 && memcmp(source+tok_start, "f80", 3) == 0) return ZIR_REF_F80_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "f128", 4) == 0) return ZIR_REF_F128_TYPE;
    if (tok_len == 9 && memcmp(source+tok_start, "anyopaque", 9) == 0) return ZIR_REF_ANYOPAQUE_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "bool", 4) == 0) return ZIR_REF_BOOL_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "void", 4) == 0) return ZIR_REF_VOID_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "type", 4) == 0) return ZIR_REF_TYPE_TYPE;
    if (tok_len == 8 && memcmp(source+tok_start, "anyerror", 8) == 0) return ZIR_REF_ANYERROR_TYPE;
    if (tok_len == 8 && memcmp(source+tok_start, "noreturn", 8) == 0) return ZIR_REF_NORETURN_TYPE;
    if (tok_len == 4 && memcmp(source+tok_start, "true", 4) == 0) return ZIR_REF_BOOL_TRUE;
    if (tok_len == 5 && memcmp(source+tok_start, "false", 5) == 0) return ZIR_REF_BOOL_FALSE;
    if (tok_len == 4 && memcmp(source+tok_start, "null", 4) == 0) return ZIR_REF_NULL_VALUE;
    if (tok_len == 9 && memcmp(source+tok_start, "undefined", 9) == 0) return ZIR_REF_UNDEF;
    // clang-format on

    // Integer type detection: u29, i13, etc. (AstGen.zig:8304-8336).
    if (tok_len >= 2
        && (source[tok_start] == 'u' || source[tok_start] == 'i')) {
        // Zig Signedness enum: unsigned=1, signed=0
        uint8_t signedness = (source[tok_start] == 'u') ? 1 : 0;
        // Reject leading zeros (e.g. u01, i007) but allow u0/i0.
        if (tok_len >= 3 && source[tok_start + 1] == '0') {
            return ZIR_REF_NONE;
        }
        uint16_t bit_count = 0;
        bool valid = true;
        for (uint32_t k = tok_start + 1; k < tok_end; k++) {
            if (source[k] >= '0' && source[k] <= '9') {
                bit_count
                    = (uint16_t)(bit_count * 10 + (uint16_t)(source[k] - '0'));
            } else {
                valid = false;
                break;
            }
        }
        if (valid) {
            ZirInstData data;
            data.int_type.src_node
                = (int32_t)node - (int32_t)gz->decl_node_index;
            data.int_type.signedness = signedness;
            data.int_type._pad = 0;
            data.int_type.bit_count = bit_count;
            return addInstruction(gz, ZIR_INST_INT_TYPE, data);
        }
    }
    return ZIR_REF_NONE;
}

// Capture tag values for packed Capture u32 (Zir.zig:3391-3435).
#define CAPTURE_TAG_NESTED 0
#define CAPTURE_TAG_INSTRUCTION 1
#define CAPTURE_TAG_INSTRUCTION_LOAD 2
#define CAPTURE_TAG_DECL_VAL 3
#define CAPTURE_TAG_DECL_REF 4

static uint32_t packCapture(uint32_t tag, uint32_t data) {
    return (tag & 0x7u) | (data << 3);
}

// Mirrors tunnelThroughClosure (AstGen.zig:8526-8624).
// Access a ZIR instruction/decl through closure. May tunnel through
// arbitrarily many namespaces, adding closure captures as required.
// Returns the ref of the closure_get instruction added to gz.
//
// capture_tag: one of CAPTURE_TAG_* constants.
// capture_data: the instruction index or NullTerminatedString index.
static uint32_t tunnelThroughClosure(GenZir* gz, uint32_t inner_ref_node,
    uint32_t num_tunnels, uint32_t capture_tag, uint32_t capture_data,
    uint32_t name_str_index) {
    // For trivial refs (instruction tag with data mapping to a non-index ref),
    // no tunnel is needed. In the upstream, this checks if
    // ref.toIndex()==null. A ref with index < ZIR_REF_START_INDEX is
    // non-indexed (e.g. void, true).
    if (capture_tag == CAPTURE_TAG_INSTRUCTION
        && capture_data + ZIR_REF_START_INDEX < ZIR_REF_START_INDEX) {
        return capture_data + ZIR_REF_START_INDEX;
    }

    // Walk gz->parent to find the namespace scopes we're tunneling through.
    // The root namespace is the outermost (first found when counting
    // num_tunnels-1 intermediate tunnels from the inside).
    // Allocate on the stack for typical small counts.
    ScopeNamespace* intermediates[16];
    ScopeNamespace** inter = intermediates;
    ScopeNamespace** inter_heap = NULL;
    if (num_tunnels > 17) {
        inter_heap = malloc((num_tunnels - 1) * sizeof(ScopeNamespace*));
        if (!inter_heap)
            exit(1);
        inter = inter_heap;
    }

    // Find the root namespace and intermediate tunnels (AstGen.zig:8568-8582).
    ScopeNamespace* root_ns = NULL;
    {
        uint32_t remaining = num_tunnels - 1;
        Scope* s = gz->parent;
        while (s != NULL && remaining > 0) {
            if (s->tag == SCOPE_NAMESPACE) {
                remaining--;
                inter[remaining] = (ScopeNamespace*)s;
            }
            s = scopeParent(s);
        }
        // Find the root namespace.
        while (s != NULL) {
            if (s->tag == SCOPE_NAMESPACE) {
                root_ns = (ScopeNamespace*)s;
                break;
            }
            s = scopeParent(s);
        }
    }

    // root_ns must have been found — we are tunneling through at least one
    // namespace, so there must be a root namespace in the scope chain.
    if (root_ns == NULL) {
        free(inter_heap);
        SET_ERROR(gz->astgen);
        return ZIR_REF_VOID_VALUE;
    }

    // Add the root capture (AstGen.zig:8584-8594).
    uint32_t root_capture = packCapture(capture_tag, capture_data);
    uint32_t cur_capture_index
        = scopeNamespaceAddCapture(root_ns, root_capture, name_str_index);

    // Chain through intermediate namespaces (AstGen.zig:8596-8616).
    for (uint32_t i = 0; i < num_tunnels - 1; i++) {
        uint32_t nested_capture
            = packCapture(CAPTURE_TAG_NESTED, cur_capture_index);
        cur_capture_index = scopeNamespaceAddCapture(
            inter[i], nested_capture, name_str_index);
    }

    free(inter_heap);

    // Add closure_get instruction (AstGen.zig:8622-8623).
    return addNodeExtendedSmall(gz, (uint16_t)ZIR_EXT_CLOSURE_GET,
        inner_ref_node, (uint16_t)cur_capture_index);
}

// Mirrors localVarRef (AstGen.zig:8367-8521).
static uint32_t localVarRef(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint32_t ident_token, uint32_t name_str) {
    AstGenCtx* ag = gz->astgen;
    uint32_t found_already = UINT32_MAX; // node index if found
    bool found_needs_tunnel = false;
    uint32_t found_namespaces_out = 0;
    uint32_t num_namespaces_out = 0;
    ScopeNamespace* capturing_namespace = NULL;

    for (Scope* s = scope; s != NULL;) {
        switch (s->tag) {
        case SCOPE_LOCAL_VAL: {
            ScopeLocalVal* lv = (ScopeLocalVal*)s;
            if (lv->name == name_str) {
                // Track usage for generic detection (AstGen.zig:8399).
                if (lv->is_used_or_discarded != NULL)
                    *lv->is_used_or_discarded = true;
                // Locals cannot shadow, no ambiguity check needed.
                uint32_t value_inst;
                if (num_namespaces_out != 0) {
                    value_inst = tunnelThroughClosure(gz, node,
                        num_namespaces_out, CAPTURE_TAG_INSTRUCTION,
                        lv->inst - ZIR_REF_START_INDEX, name_str);
                } else {
                    value_inst = lv->inst;
                }
                return rvalueNoCoercePreRef(gz, rl, value_inst, node);
            }
            s = lv->parent;
            continue;
        }
        case SCOPE_LOCAL_PTR: {
            ScopeLocalPtr* lp = (ScopeLocalPtr*)s;
            if (lp->name == name_str) {
                // Can't close over a runtime variable
                // (AstGen.zig:8424-8432).
                if (num_namespaces_out != 0 && !lp->maybe_comptime
                    && !gz->is_typeof) {
                    SET_ERROR(ag);
                    return ZIR_REF_VOID_VALUE;
                }
                if (RL_IS_REF(rl)) {
                    uint32_t ptr_inst;
                    if (num_namespaces_out != 0) {
                        ptr_inst = tunnelThroughClosure(gz, node,
                            num_namespaces_out, CAPTURE_TAG_INSTRUCTION,
                            lp->ptr - ZIR_REF_START_INDEX, name_str);
                    } else {
                        ptr_inst = lp->ptr;
                    }
                    return ptr_inst;
                } else {
                    uint32_t val_inst;
                    if (num_namespaces_out != 0) {
                        val_inst = tunnelThroughClosure(gz, node,
                            num_namespaces_out, CAPTURE_TAG_INSTRUCTION_LOAD,
                            lp->ptr - ZIR_REF_START_INDEX, name_str);
                    } else {
                        val_inst = addUnNode(gz, ZIR_INST_LOAD, lp->ptr, node);
                    }
                    return rvalueNoCoercePreRef(gz, rl, val_inst, node);
                }
            }
            s = lp->parent;
            continue;
        }
        case SCOPE_GEN_ZIR: {
            s = ((GenZir*)s)->parent;
            continue;
        }
        case SCOPE_DEFER_NORMAL:
        case SCOPE_DEFER_ERROR: {
            s = ((ScopeDefer*)s)->parent;
            continue;
        }
        case SCOPE_LABEL: {
            s = ((ScopeLabel*)s)->parent;
            continue;
        }
        case SCOPE_NAMESPACE: {
            // Check namespace decls, then continue walking
            // (AstGen.zig:8455-8472).
            ScopeNamespace* ns = (ScopeNamespace*)s;
            uint32_t decl_node = scopeNamespaceFindDecl(ns, name_str);
            if (decl_node != UINT32_MAX) {
                if (found_already != UINT32_MAX) {
                    // Ambiguous reference (AstGen.zig:8458-8462).
                    SET_ERROR(ag);
                    return ZIR_REF_VOID_VALUE;
                }
                found_already = decl_node;
                found_needs_tunnel = ns->maybe_generic;
                found_namespaces_out = num_namespaces_out;
            }
            num_namespaces_out++;
            capturing_namespace = ns;
            s = ns->parent;
            continue;
        }
        case SCOPE_TOP:
            goto done_walk;
        }
    }
done_walk:
    (void)capturing_namespace;

    if (found_already == UINT32_MAX) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Decl references (AstGen.zig:8484-8520).
    if (found_namespaces_out > 0 && found_needs_tunnel) {
        if (RL_IS_REF(rl)) {
            return tunnelThroughClosure(gz, node, found_namespaces_out,
                CAPTURE_TAG_DECL_REF, name_str, name_str);
        } else {
            uint32_t result
                = tunnelThroughClosure(gz, node, found_namespaces_out,
                    CAPTURE_TAG_DECL_VAL, name_str, name_str);
            return rvalueNoCoercePreRef(gz, rl, result, node);
        }
    }

    // Simple decl reference (AstGen.zig:8512-8520).
    ZirInstData data;
    data.str_tok.start = name_str;
    data.str_tok.src_tok = tokenIndexToRelative(gz, ident_token);
    if (RL_IS_REF(rl)) {
        return addInstruction(gz, ZIR_INST_DECL_REF, data);
    } else {
        uint32_t result = addInstruction(gz, ZIR_INST_DECL_VAL, data);
        return rvalueNoCoercePreRef(gz, rl, result, node);
    }
}

static uint32_t identifierExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    uint32_t ident_token = ag->tree->nodes.main_tokens[node];

    // Check for primitive types FIRST (AstGen.zig:8298-8338).
    uint32_t prim = tryResolvePrimitiveIdent(gz, node);
    if (prim != ZIR_REF_NONE)
        return rvalue(gz, rl, prim, node);

    // Local variables and container-level declarations
    // (AstGen.zig:8340-8365).
    return localVarRef(
        gz, scope, rl, node, ident_token, identAsString(ag, ident_token));
}

// --- fieldAccess (AstGen.zig:6154) ---
// Simplified: emits field_val instruction with Field payload.

static uint32_t fieldAccessExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];

    // data.lhs = object node, data.rhs = field identifier token.
    uint32_t object_node = nd.lhs;
    uint32_t field_ident = nd.rhs;

    // Get field name as string (AstGen.zig:6180).
    uint32_t str_index = identAsString(ag, field_ident);

    // Evaluate the LHS object expression (AstGen.zig:6181).
    // For .ref rl, LHS is also evaluated with .ref (AstGen.zig:6161).
    ResultLoc lhs_rl = (RL_IS_REF(rl)) ? RL_REF_VAL : RL_NONE_VAL;
    uint32_t lhs = exprRl(gz, scope, lhs_rl, object_node);

    // Emit dbg_stmt for the dot token (AstGen.zig:6183-6184).
    advanceSourceCursorToMainToken(ag, gz, node);
    {
        uint32_t line = ag->source_line - gz->decl_line;
        uint32_t column = ag->source_column;
        emitDbgStmt(gz, line, column);
    }

    // Emit field_val instruction with Field payload (AstGen.zig:6186-6189).
    ensureExtraCapacity(ag, 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = lhs; // Field.lhs
    ag->extra[ag->extra_len++] = str_index; // Field.field_name_start

    // .ref → field_ptr, else → field_val (AstGen.zig:6160-6164).
    ZirInstTag ftag
        = (RL_IS_REF(rl)) ? ZIR_INST_FIELD_PTR : ZIR_INST_FIELD_VAL;
    ZirInstData data;
    data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    uint32_t access = addInstruction(gz, ftag, data);
    // For ref, return directly; otherwise apply rvalue (AstGen.zig:6161-6164).
    if (RL_IS_REF(rl))
        return access;
    return rvalue(gz, rl, access, node);
}

// --- ptrType (AstGen.zig:3833) ---

static uint32_t ptrTypeExpr(GenZir* gz, Scope* scope, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];
    uint32_t main_tok = tree->nodes.main_tokens[node];

    // child_type is always in rhs for all ptr_type variants.
    uint32_t child_type_node = nd.rhs;

    // Determine size from main_token (Ast.zig:2122-2131).
    // Pointer.Size: one=0, many=1, slice=2, c=3.
    uint8_t size;
    TokenizerTag main_tok_tag = tree->tokens.tags[main_tok];
    if (main_tok_tag == TOKEN_ASTERISK
        || main_tok_tag == TOKEN_ASTERISK_ASTERISK) {
        size = 0; // one
    } else {
        assert(main_tok_tag == TOKEN_L_BRACKET);
        TokenizerTag next_tag = tree->tokens.tags[main_tok + 1];
        if (next_tag == TOKEN_ASTERISK) {
            // [*c]T vs [*]T: c-pointer if next-next is identifier.
            if (tree->tokens.tags[main_tok + 2] == TOKEN_IDENTIFIER)
                size = 3; // c
            else
                size = 1; // many
        } else {
            size = 2; // slice
        }
    }

    // Determine sentinel, align, addrspace, bit_range nodes from AST variant
    // (Ast.zig:1656-1696).
    uint32_t sentinel_node = UINT32_MAX;
    uint32_t align_node = UINT32_MAX;
    uint32_t addrspace_node = UINT32_MAX;
    uint32_t bit_range_start = UINT32_MAX;
    uint32_t bit_range_end = UINT32_MAX;

    if (tag == AST_NODE_PTR_TYPE_ALIGNED) {
        // opt_node_and_node: lhs = optional align_node (0=none), rhs = child.
        if (nd.lhs != 0)
            align_node = nd.lhs;
    } else if (tag == AST_NODE_PTR_TYPE_SENTINEL) {
        // opt_node_and_node: lhs = optional sentinel (0=none), rhs = child.
        if (nd.lhs != 0)
            sentinel_node = nd.lhs;
    } else if (tag == AST_NODE_PTR_TYPE) {
        // extra_and_node: lhs = extra index to AstPtrType, rhs = child_type.
        const AstPtrType* pt
            = (const AstPtrType*)(tree->extra_data.arr + nd.lhs);
        if (pt->sentinel != UINT32_MAX)
            sentinel_node = pt->sentinel;
        if (pt->align_node != UINT32_MAX)
            align_node = pt->align_node;
        if (pt->addrspace_node != UINT32_MAX)
            addrspace_node = pt->addrspace_node;
    } else if (tag == AST_NODE_PTR_TYPE_BIT_RANGE) {
        // extra_and_node: lhs = extra index to AstPtrTypeBitRange.
        const AstPtrTypeBitRange* pt
            = (const AstPtrTypeBitRange*)(tree->extra_data.arr + nd.lhs);
        if (pt->sentinel != UINT32_MAX)
            sentinel_node = pt->sentinel;
        align_node = pt->align_node;
        if (pt->addrspace_node != UINT32_MAX)
            addrspace_node = pt->addrspace_node;
        bit_range_start = pt->bit_range_start;
        bit_range_end = pt->bit_range_end;
    }

    // Scan tokens between main_token and child_type to find const/volatile/
    // allowzero (Ast.zig:2139-2164).
    bool has_const = false;
    bool has_volatile = false;
    bool has_allowzero = false;
    {
        uint32_t i;
        if (sentinel_node != UINT32_MAX) {
            i = lastToken(tree, sentinel_node) + 1;
        } else if (size == 1 || size == 3) {
            // many or c: start after main_token.
            i = main_tok + 1;
        } else {
            i = main_tok;
        }
        uint32_t end = firstToken(tree, child_type_node);
        while (i < end) {
            TokenizerTag tt = tree->tokens.tags[i];
            if (tt == TOKEN_KEYWORD_ALLOWZERO) {
                has_allowzero = true;
            } else if (tt == TOKEN_KEYWORD_CONST) {
                has_const = true;
            } else if (tt == TOKEN_KEYWORD_VOLATILE) {
                has_volatile = true;
            } else if (tt == TOKEN_KEYWORD_ALIGN) {
                // Skip over align expression.
                if (bit_range_end != UINT32_MAX)
                    i = lastToken(tree, bit_range_end) + 1;
                else if (align_node != UINT32_MAX)
                    i = lastToken(tree, align_node) + 1;
            }
            i++;
        }
    }

    // C pointers always allow address zero (AstGen.zig:3840-3842).
    if (size == 3 && has_allowzero) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Save source cursor before typeExpr so we can restore it before each
    // trailing expression (AstGen.zig:3844-3846).
    uint32_t saved_source_offset = ag->source_offset;
    uint32_t saved_source_line = ag->source_line;
    uint32_t saved_source_column = ag->source_column;

    // Evaluate element type (AstGen.zig:3847).
    uint32_t elem_type = typeExpr(gz, scope, child_type_node);

    // Evaluate trailing expressions (AstGen.zig:3856-3897).
    uint32_t sentinel_ref = ZIR_REF_NONE;
    uint32_t align_ref = ZIR_REF_NONE;
    uint32_t addrspace_ref = ZIR_REF_NONE;
    uint32_t bit_start_ref = ZIR_REF_NONE;
    uint32_t bit_end_ref = ZIR_REF_NONE;
    uint32_t trailing_count = 0;

    if (sentinel_node != UINT32_MAX) {
        // Restore source cursor (AstGen.zig:3859-3861).
        ag->source_offset = saved_source_offset;
        ag->source_line = saved_source_line;
        ag->source_column = saved_source_column;
        uint32_t reason = (size == 2) ? COMPTIME_REASON_SLICE_SENTINEL
                                      : COMPTIME_REASON_POINTER_SENTINEL;
        ResultLoc srl = {
            .tag = RL_TY, .data = elem_type, .src_node = 0, .ctx = RI_CTX_NONE
        };
        sentinel_ref = comptimeExpr(gz, scope, srl, sentinel_node, reason);
        trailing_count++;
    }
    if (addrspace_node != UINT32_MAX) {
        // Restore source cursor (AstGen.zig:3876-3878).
        ag->source_offset = saved_source_offset;
        ag->source_line = saved_source_line;
        ag->source_column = saved_source_column;
        // Upstream creates addrspace_ty via addBuiltinValue, we don't have
        // that yet, so pass RL_NONE (matching previous behavior).
        addrspace_ref = comptimeExpr(
            gz, scope, RL_NONE_VAL, addrspace_node, COMPTIME_REASON_ADDRSPACE);
        trailing_count++;
    }
    if (align_node != UINT32_MAX) {
        // Restore source cursor (AstGen.zig:3885-3887).
        ag->source_offset = saved_source_offset;
        ag->source_line = saved_source_line;
        ag->source_column = saved_source_column;
        ResultLoc arl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_U29_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        align_ref
            = comptimeExpr(gz, scope, arl, align_node, COMPTIME_REASON_ALIGN);
        trailing_count++;
    }
    if (bit_range_start != UINT32_MAX) {
        ResultLoc brl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_U16_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        bit_start_ref = comptimeExpr(
            gz, scope, brl, bit_range_start, COMPTIME_REASON_TYPE);
        bit_end_ref = comptimeExpr(
            gz, scope, brl, bit_range_end, COMPTIME_REASON_TYPE);
        trailing_count += 2;
    }

    // Build PtrType payload: { elem_type, src_node } + trailing
    // (AstGen.zig:3905-3921).
    ensureExtraCapacity(ag, 2 + trailing_count);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = elem_type;
    ag->extra[ag->extra_len++]
        = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
    if (sentinel_ref != ZIR_REF_NONE)
        ag->extra[ag->extra_len++] = sentinel_ref;
    if (align_ref != ZIR_REF_NONE)
        ag->extra[ag->extra_len++] = align_ref;
    if (addrspace_ref != ZIR_REF_NONE)
        ag->extra[ag->extra_len++] = addrspace_ref;
    if (bit_start_ref != ZIR_REF_NONE) {
        ag->extra[ag->extra_len++] = bit_start_ref;
        ag->extra[ag->extra_len++] = bit_end_ref;
    }

    // Build flags packed byte (AstGen.zig:3927-3934).
    uint8_t flags = 0;
    if (has_allowzero)
        flags |= (1 << 0); // is_allowzero
    if (!has_const)
        flags |= (1 << 1); // is_mutable
    if (has_volatile)
        flags |= (1 << 2); // is_volatile
    if (sentinel_ref != ZIR_REF_NONE)
        flags |= (1 << 3); // has_sentinel
    if (align_ref != ZIR_REF_NONE)
        flags |= (1 << 4); // has_align
    if (addrspace_ref != ZIR_REF_NONE)
        flags |= (1 << 5); // has_addrspace
    if (bit_start_ref != ZIR_REF_NONE)
        flags |= (1 << 6); // has_bit_range

    ZirInstData data;
    data.ptr_type.flags = flags;
    data.ptr_type.size = size;
    data.ptr_type._pad = 0;
    data.ptr_type.payload_index = payload_index;
    return addInstruction(gz, ZIR_INST_PTR_TYPE, data);
}

// --- arrayType (AstGen.zig:940) ---

static uint32_t arrayTypeExpr(GenZir* gz, Scope* scope, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];

    // data.lhs = length expr node, data.rhs = element type node.
    // Check for `_` identifier → compile error (AstGen.zig:3950-3953).
    if (tree->nodes.tags[nd.lhs] == AST_NODE_IDENTIFIER
        && isUnderscoreIdent(tree, nd.lhs)) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }
    ResultLoc len_rl = { .tag = RL_COERCED_TY,
        .data = ZIR_REF_USIZE_TYPE,
        .src_node = 0,
        .ctx = RI_CTX_NONE };
    uint32_t len
        = comptimeExpr(gz, scope, len_rl, nd.lhs, COMPTIME_REASON_TYPE);
    uint32_t elem_type = typeExpr(gz, scope, nd.rhs);
    return addPlNodeBin(gz, ZIR_INST_ARRAY_TYPE, node, len, elem_type);
}

// --- arrayInitExpr (AstGen.zig:1431) ---
// Handles typed array init: [_]T{...}, [_:s]T{...}, and [N]T{...}.

static uint32_t arrayInitExprTyped(GenZir* gz, Scope* scope, uint32_t node,
    const uint32_t* elements, uint32_t elem_count, uint32_t ty_inst,
    uint32_t elem_ty, bool is_ref);

static uint32_t arrayInitExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Get elements and type expression based on the variant.
    uint32_t type_expr_node = 0;
    uint32_t elem_buf[2];
    const uint32_t* elements = NULL;
    uint32_t elem_count = 0;

    switch (tag) {
    case AST_NODE_ARRAY_INIT_ONE:
    case AST_NODE_ARRAY_INIT_ONE_COMMA: {
        type_expr_node = nd.lhs;
        if (nd.rhs != 0) {
            elem_buf[0] = nd.rhs;
            elements = elem_buf;
            elem_count = 1;
        }
        break;
    }
    case AST_NODE_ARRAY_INIT:
    case AST_NODE_ARRAY_INIT_COMMA: {
        // data = node_and_extra: lhs = type_expr, rhs = extra_index.
        // extra[rhs] = SubRange.start, extra[rhs+1] = SubRange.end.
        // Elements are extra_data[start..end].
        type_expr_node = nd.lhs;
        uint32_t extra_idx = nd.rhs;
        uint32_t range_start = tree->extra_data.arr[extra_idx];
        uint32_t range_end = tree->extra_data.arr[extra_idx + 1];
        elements = tree->extra_data.arr + range_start;
        elem_count = range_end - range_start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    if (type_expr_node == 0 || elem_count == 0) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Determine array_ty and elem_ty (AstGen.zig:1443-1482).
    uint32_t array_ty = ZIR_REF_NONE;
    uint32_t elem_ty = ZIR_REF_NONE;

    // Check if the type is [_]T or [_:s]T (inferred length)
    // (AstGen.zig:1446-1474, fullArrayType handles both array_type and
    // array_type_sentinel).
    AstNodeTag type_tag = tree->nodes.tags[type_expr_node];
    if (type_tag == AST_NODE_ARRAY_TYPE
        || type_tag == AST_NODE_ARRAY_TYPE_SENTINEL) {
        AstData type_nd = tree->nodes.datas[type_expr_node];
        uint32_t elem_count_node = type_nd.lhs;

        // This intentionally does not support `@"_"` syntax.
        if (tree->nodes.tags[elem_count_node] == AST_NODE_IDENTIFIER
            && isUnderscoreIdent(tree, elem_count_node)) {
            // Inferred length: addInt(elem_count) (AstGen.zig:1452).
            uint32_t len_inst = addInt(gz, elem_count);

            if (type_tag == AST_NODE_ARRAY_TYPE) {
                // [_]T: elem_type_node is rhs (AstGen.zig:1454-1459).
                uint32_t elem_type_node = type_nd.rhs;
                elem_ty = typeExpr(gz, scope, elem_type_node);
                array_ty = addPlNodeBin(gz, ZIR_INST_ARRAY_TYPE,
                    type_expr_node, len_inst, elem_ty);
            } else {
                // [_:s]T: sentinel and elem_type from extra data
                // (AstGen.zig:1460-1473).
                uint32_t sentinel_node = tree->extra_data.arr[type_nd.rhs];
                uint32_t elem_type_node
                    = tree->extra_data.arr[type_nd.rhs + 1];
                elem_ty = typeExpr(gz, scope, elem_type_node);
                ResultLoc sent_rl = { .tag = RL_TY,
                    .data = elem_ty,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                uint32_t sentinel = comptimeExpr(gz, scope, sent_rl,
                    sentinel_node, COMPTIME_REASON_ARRAY_SENTINEL);
                array_ty = addPlNodeTriple(gz, ZIR_INST_ARRAY_TYPE_SENTINEL,
                    type_expr_node, len_inst, elem_ty, sentinel);
            }
            goto typed_init;
        }
    }

    // Non-inferred length: evaluate type normally (AstGen.zig:1476-1481).
    array_ty = typeExpr(gz, scope, type_expr_node);
    // validate_array_init_ty: ArrayInit{ty, init_count}
    addPlNodeBin(
        gz, ZIR_INST_VALIDATE_ARRAY_INIT_TY, node, array_ty, elem_count);
    elem_ty = ZIR_REF_NONE;

typed_init:
    // Typed inits do not use RLS for language simplicity
    // (AstGen.zig:1484-1513).
    if (rl.tag == RL_DISCARD) {
        // discard RL: evaluate elements but don't emit array_init
        // (AstGen.zig:1487-1506).
        if (elem_ty != ZIR_REF_NONE) {
            ResultLoc elem_rl
                = { .tag = RL_TY, .data = elem_ty, .src_node = 0 };
            for (uint32_t i = 0; i < elem_count; i++) {
                exprRl(gz, scope, elem_rl, elements[i]);
            }
        } else {
            for (uint32_t i = 0; i < elem_count; i++) {
                uint32_t this_elem_ty
                    = addBin(gz, ZIR_INST_ARRAY_INIT_ELEM_TYPE, array_ty, i);
                ResultLoc elem_rl
                    = { .tag = RL_TY, .data = this_elem_ty, .src_node = 0 };
                exprRl(gz, scope, elem_rl, elements[i]);
            }
        }
        return ZIR_REF_VOID_VALUE;
    }

    if (rl.tag == RL_REF) {
        // ref RL: arrayInitExprTyped with is_ref=true
        // (AstGen.zig:1507).
        return arrayInitExprTyped(
            gz, scope, node, elements, elem_count, array_ty, elem_ty, true);
    }

    // All other RLs: arrayInitExprTyped + rvalue (AstGen.zig:1508-1511).
    uint32_t array_inst = arrayInitExprTyped(
        gz, scope, node, elements, elem_count, array_ty, elem_ty, false);
    return rvalue(gz, rl, array_inst, node);
}

// arrayInitExprTyped (AstGen.zig:1598-1642).
// Emits array_init or array_init_ref instruction.
static uint32_t arrayInitExprTyped(GenZir* gz, Scope* scope, uint32_t node,
    const uint32_t* elements, uint32_t elem_count, uint32_t ty_inst,
    uint32_t elem_ty, bool is_ref) {
    AstGenCtx* ag = gz->astgen;
    uint32_t operands_len = elem_count + 1; // +1 for type
    ensureExtraCapacity(ag, 1 + operands_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = operands_len;
    ag->extra[ag->extra_len++] = ty_inst;
    uint32_t extra_start = ag->extra_len;
    ag->extra_len += elem_count;

    if (elem_ty != ZIR_REF_NONE) {
        // Known elem type: use coerced_ty RL (AstGen.zig:1617-1623).
        ResultLoc elem_rl
            = { .tag = RL_COERCED_TY, .data = elem_ty, .src_node = 0 };
        for (uint32_t i = 0; i < elem_count; i++) {
            uint32_t elem_ref = exprRl(gz, scope, elem_rl, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
    } else {
        // Unknown elem type: use array_init_elem_type per element
        // (AstGen.zig:1625-1637).
        for (uint32_t i = 0; i < elem_count; i++) {
            uint32_t this_elem_ty
                = addBin(gz, ZIR_INST_ARRAY_INIT_ELEM_TYPE, ty_inst, i);
            ResultLoc elem_rl = {
                .tag = RL_COERCED_TY, .data = this_elem_ty, .src_node = 0
            };
            uint32_t elem_ref = exprRl(gz, scope, elem_rl, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
    }

    ZirInstTag init_tag
        = is_ref ? ZIR_INST_ARRAY_INIT_REF : ZIR_INST_ARRAY_INIT;
    return addPlNodePayloadIndex(gz, init_tag, node, payload_index);
}

// --- simpleBinOp (AstGen.zig:2204) ---

static uint32_t simpleBinOp(
    GenZir* gz, Scope* scope, uint32_t node, ZirInstTag op_tag) {
    AstGenCtx* ag = gz->astgen;
    AstData nd = ag->tree->nodes.datas[node];
    uint32_t lhs = exprRl(gz, scope, RL_NONE_VAL, nd.lhs);
    // For arithmetic ops, advance cursor before RHS (AstGen.zig:6245-6256).
    uint32_t saved_line = 0, saved_col = 0;
    bool need_dbg = false;
    if (op_tag == ZIR_INST_ADD || op_tag == ZIR_INST_SUB
        || op_tag == ZIR_INST_MUL || op_tag == ZIR_INST_DIV
        || op_tag == ZIR_INST_MOD_REM) {
        if (!gz->is_comptime) {
            advanceSourceCursorToMainToken(ag, gz, node);
        }
        saved_line = ag->source_line - gz->decl_line;
        saved_col = ag->source_column;
        need_dbg = true;
    }
    uint32_t rhs = exprRl(gz, scope, RL_NONE_VAL, nd.rhs);
    if (need_dbg) {
        emitDbgStmt(gz, saved_line, saved_col);
    }
    return addPlNodeBin(gz, op_tag, node, lhs, rhs);
}

// --- shiftOp (AstGen.zig:9978) ---

static uint32_t shiftOp(
    GenZir* gz, Scope* scope, uint32_t node, ZirInstTag tag) {
    AstGenCtx* ag = gz->astgen;
    AstData nd = ag->tree->nodes.datas[node];
    uint32_t lhs = exprRl(gz, scope, RL_NONE_VAL, nd.lhs);

    advanceSourceCursorToMainToken(ag, gz, node);
    uint32_t saved_line = ag->source_line - gz->decl_line;
    uint32_t saved_col = ag->source_column;

    uint32_t log2_int_type
        = addUnNode(gz, ZIR_INST_TYPEOF_LOG2_INT_TYPE, lhs, nd.lhs);
    ResultLoc rhs_rl = { .tag = RL_TY,
        .data = log2_int_type,
        .src_node = 0,
        .ctx = RI_CTX_SHIFT_OP };
    uint32_t rhs = exprRl(gz, scope, rhs_rl, nd.rhs);

    emitDbgStmt(gz, saved_line, saved_col);

    return addPlNodeBin(gz, tag, node, lhs, rhs);
}

// --- multilineStringLiteral (AstGen.zig:8645) ---
// Port of strLitNodeAsString for multiline strings.
static uint32_t multilineStringLiteral(
    GenZir* gz, Scope* scope, uint32_t node) {
    (void)scope;
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];
    uint32_t start_tok = nd.lhs;
    uint32_t end_tok = nd.rhs;

    uint32_t str_index = ag->string_bytes_len;

    // First line: no preceding newline.
    for (uint32_t tok_i = start_tok; tok_i <= end_tok; tok_i++) {
        uint32_t tok_start = tree->tokens.starts[tok_i];
        const char* source = tree->source;
        // Skip leading `\\` (2 chars).
        uint32_t content_start = tok_start + 2;
        // Find end of line.
        uint32_t content_end = content_start;
        while (content_end < tree->source_len && source[content_end] != '\n')
            content_end++;
        uint32_t line_len = content_end - content_start;

        if (tok_i > start_tok) {
            // Prepend newline for lines after the first.
            ensureStringBytesCapacity(ag, line_len + 1);
            ag->string_bytes[ag->string_bytes_len++] = '\n';
        } else {
            ensureStringBytesCapacity(ag, line_len);
        }
        memcpy(ag->string_bytes + ag->string_bytes_len, source + content_start,
            line_len);
        ag->string_bytes_len += line_len;
    }

    uint32_t len = ag->string_bytes_len - str_index;
    ensureStringBytesCapacity(ag, 1);
    ag->string_bytes[ag->string_bytes_len++] = 0; // null terminator

    ZirInstData data;
    data.str.start = str_index;
    data.str.len = len;
    return addInstruction(gz, ZIR_INST_STR, data);
}

// --- ret (AstGen.zig:8119) ---
static uint32_t retExpr(GenZir* gz, Scope* scope, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    // AstGen.zig:8123: return outside function is an error.
    if (ag->fn_block == NULL) {
        SET_ERROR(ag);
        return ZIR_REF_UNREACHABLE_VALUE;
    }

    // AstGen.zig:8127-8135: cannot return from defer expression.
    if (gz->any_defer_node != UINT32_MAX) {
        SET_ERROR(ag);
        return ZIR_REF_UNREACHABLE_VALUE;
    }

    // Ensure debug line/column information is emitted for this return
    // expression (AstGen.zig:8141-8144).
    if (!gz->is_comptime) {
        emitDbgNode(gz, node);
    }
    uint32_t ret_lc_line = ag->source_line - gz->decl_line;
    uint32_t ret_lc_column = ag->source_column;

    const Scope* defer_outer = &((GenZir*)ag->fn_block)->base;

    AstData nd = tree->nodes.datas[node];
    uint32_t operand_node = nd.lhs; // optional

    if (operand_node == 0) {
        // Void return (AstGen.zig:8148-8156).
        genDefers(gz, defer_outer, scope, DEFER_NORMAL_ONLY);
        // Restore error trace unconditionally (AstGen.zig:8153).
        ZirInstData rdata;
        rdata.un_node.operand = ZIR_REF_NONE;
        rdata.un_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        addInstruction(
            gz, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);
        addUnNode(gz, ZIR_INST_RET_NODE, ZIR_REF_VOID_VALUE, node);
        return ZIR_REF_UNREACHABLE_VALUE;
    }

    // Fast path: return error.Foo (AstGen.zig:8159-8175).
    if (tree->nodes.tags[operand_node] == AST_NODE_ERROR_VALUE) {
        uint32_t error_token = tree->nodes.main_tokens[operand_node] + 2;
        uint32_t err_name_str = identAsString(ag, error_token);
        DeferCounts dc = countDefers(defer_outer, scope);
        if (!dc.need_err_code) {
            genDefers(gz, defer_outer, scope, DEFER_BOTH_SANS_ERR);
            emitDbgStmt(gz, ret_lc_line, ret_lc_column);
            addStrTok(gz, ZIR_INST_RET_ERR_VALUE, err_name_str, error_token);
            return ZIR_REF_UNREACHABLE_VALUE;
        }
        // need_err_code path: not implemented yet, fall through to general.
    }

    // Evaluate operand with result location (AstGen.zig:8178-8186).
    // If nodes_need_rl contains this return node, use ptr-based RL;
    // otherwise use coerced_ty.
    ResultLoc ret_rl = RL_NONE_VAL;
    bool use_ptr = nodesNeedRlContains(ag, node);
    uint32_t ret_ptr_inst = 0;
    if (use_ptr) {
        // Create ret_ptr instruction (AstGen.zig:8179).
        ZirInstData rpdata;
        rpdata.node = (int32_t)node - (int32_t)gz->decl_node_index;
        ret_ptr_inst = addInstruction(gz, ZIR_INST_RET_PTR, rpdata);
        ret_rl.tag = RL_PTR;
        ret_rl.data = ret_ptr_inst;
    } else if (ag->fn_ret_ty != 0) {
        ret_rl.tag = RL_COERCED_TY;
        ret_rl.data = ag->fn_ret_ty;
    }
    ret_rl.ctx = RI_CTX_RETURN;
    // nameStratExpr with .func name strategy (AstGen.zig:8185).
    uint32_t operand;
    if (!nameStratExpr(
            gz, scope, ret_rl, operand_node, 1 /* func */, &operand)) {
        operand = reachableExpr(gz, scope, ret_rl, operand_node, node);
    }

    // Emit RESTORE_ERR_RET_INDEX based on nodeMayEvalToError
    // (AstGen.zig:8188-8253).
    int eval_to_err = nodeMayEvalToError(tree, operand_node);
    if (eval_to_err == EVAL_TO_ERROR_NEVER) {
        // Returning non-error: pop error trace unconditionally
        // (AstGen.zig:8190-8198).
        genDefers(gz, defer_outer, scope, DEFER_NORMAL_ONLY);
        ZirInstData rdata;
        rdata.un_node.operand = ZIR_REF_NONE;
        rdata.un_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        addInstruction(
            gz, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);
        emitDbgStmt(gz, ret_lc_line, ret_lc_column);
        // addRet (AstGen.zig:13188-13194).
        if (use_ptr) {
            addUnNode(gz, ZIR_INST_RET_LOAD, ret_ptr_inst, node);
        } else {
            addUnNode(gz, ZIR_INST_RET_NODE, operand, node);
        }
        return ZIR_REF_UNREACHABLE_VALUE;
    } else if (eval_to_err == EVAL_TO_ERROR_ALWAYS) {
        // .always: emit both error defers and regular defers
        // (AstGen.zig:8200-8206).
        uint32_t err_code = use_ptr
            ? addUnNode(gz, ZIR_INST_LOAD, ret_ptr_inst, node)
            : operand;
        (void)err_code;
        // TODO: genDefers with .both = err_code when errdefer is implemented.
        genDefers(gz, defer_outer, scope, DEFER_NORMAL_ONLY);
        emitDbgStmt(gz, ret_lc_line, ret_lc_column);
        if (use_ptr) {
            addUnNode(gz, ZIR_INST_RET_LOAD, ret_ptr_inst, node);
        } else {
            addUnNode(gz, ZIR_INST_RET_NODE, operand, node);
        }
        return ZIR_REF_UNREACHABLE_VALUE;
    } else {
        // .maybe (AstGen.zig:8208-8252).
        DeferCounts dc = countDefers(defer_outer, scope);
        if (!dc.have_err) {
            // Only regular defers; no branch needed (AstGen.zig:8210-8220).
            genDefers(gz, defer_outer, scope, DEFER_NORMAL_ONLY);
            emitDbgStmt(gz, ret_lc_line, ret_lc_column);
            uint32_t result = use_ptr
                ? addUnNode(gz, ZIR_INST_LOAD, ret_ptr_inst, node)
                : operand;
            ZirInstData rdata;
            rdata.un_node.operand = result;
            rdata.un_node.src_node
                = (int32_t)node - (int32_t)gz->decl_node_index;
            addInstruction(gz, ZIR_INST_RESTORE_ERR_RET_INDEX_FN_ENTRY, rdata);
            if (use_ptr) {
                addUnNode(gz, ZIR_INST_RET_LOAD, ret_ptr_inst, node);
            } else {
                addUnNode(gz, ZIR_INST_RET_NODE, operand, node);
            }
            return ZIR_REF_UNREACHABLE_VALUE;
        }
        // have_err path: emit conditional branch (not yet implemented).
        // Fall through to simplified path.
        genDefers(gz, defer_outer, scope, DEFER_NORMAL_ONLY);
        emitDbgStmt(gz, ret_lc_line, ret_lc_column);
        if (use_ptr) {
            addUnNode(gz, ZIR_INST_RET_LOAD, ret_ptr_inst, node);
        } else {
            addUnNode(gz, ZIR_INST_RET_NODE, operand, node);
        }
        return ZIR_REF_UNREACHABLE_VALUE;
    }
}

// --- calleeExpr (AstGen.zig:10183) ---
// Returns: 0 = direct call, 1 = field call.

typedef struct {
    bool is_field;
    uint32_t obj_ptr; // for field calls: ref to object
    uint32_t field_name_start; // for field calls: string index
    uint32_t direct; // for direct calls: ref to callee
} Callee;

static Callee calleeExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t fn_expr_node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[fn_expr_node];

    if (tag == AST_NODE_FIELD_ACCESS) {
        AstData nd = tree->nodes.datas[fn_expr_node];
        uint32_t object_node = nd.lhs;
        uint32_t field_ident = nd.rhs;
        uint32_t str_index = identAsString(ag, field_ident);
        // Evaluate object with .ref rl (AstGen.zig:10207).
        uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, object_node);

        // Advance to main token (the `.` dot) — not first token
        // (AstGen.zig:10209).
        advanceSourceCursorToMainToken(ag, gz, fn_expr_node);
        {
            uint32_t line = ag->source_line - gz->decl_line;
            uint32_t column = ag->source_column;
            emitDbgStmt(gz, line, column);
        }

        Callee c;
        c.is_field = true;
        c.obj_ptr = lhs;
        c.field_name_start = str_index;
        c.direct = 0;
        return c;
    }

    // enum_literal callee: decl literal call syntax (AstGen.zig:10217-10233).
    if (tag == AST_NODE_ENUM_LITERAL) {
        uint32_t res_ty = rlResultType(gz, rl, fn_expr_node);
        if (res_ty != 0) {
            uint32_t str_index
                = identAsString(ag, tree->nodes.main_tokens[fn_expr_node]);
            uint32_t callee = addPlNodeBin(gz, ZIR_INST_DECL_LITERAL_NO_COERCE,
                fn_expr_node, res_ty, str_index);
            Callee c;
            c.is_field = false;
            c.direct = callee;
            c.obj_ptr = 0;
            c.field_name_start = 0;
            return c;
        }
        // No result type: fall through to expr with rl=none.
    }

    // Default: direct call (AstGen.zig:10235).
    Callee c;
    c.is_field = false;
    c.direct = expr(gz, scope, fn_expr_node);
    c.obj_ptr = 0;
    c.field_name_start = 0;
    return c;
}

// --- callExpr (AstGen.zig:10058) ---
static uint32_t callExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract callee and args from AST.
    uint32_t fn_expr_node;
    uint32_t arg_buf[2];
    const uint32_t* args = NULL;
    uint32_t args_len = 0;
    uint32_t lparen_tok;

    switch (tag) {
    case AST_NODE_CALL_ONE:
    case AST_NODE_CALL_ONE_COMMA: {
        fn_expr_node = nd.lhs;
        lparen_tok = tree->nodes.main_tokens[node];
        if (nd.rhs != 0) {
            arg_buf[0] = nd.rhs;
            args = arg_buf;
            args_len = 1;
        }
        break;
    }
    case AST_NODE_CALL:
    case AST_NODE_CALL_COMMA: {
        fn_expr_node = nd.lhs;
        lparen_tok = tree->nodes.main_tokens[node];
        uint32_t extra_idx = nd.rhs;
        uint32_t range_start = tree->extra_data.arr[extra_idx];
        uint32_t range_end = tree->extra_data.arr[extra_idx + 1];
        args = tree->extra_data.arr + range_start;
        args_len = range_end - range_start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    Callee callee = calleeExpr(gz, scope, rl, fn_expr_node);

    // dbg_stmt before call (AstGen.zig:10078-10083).
    {
        advanceSourceCursor(ag, tree->tokens.starts[lparen_tok]);
        uint32_t line = ag->source_line - gz->decl_line;
        uint32_t column = ag->source_column;
        emitDbgStmtForceCurrentIndex(gz, line, column);
    }

    // Reserve instruction slot for call (AstGen.zig:10093).
    uint32_t call_index = ag->inst_len;
    ensureInstCapacity(ag, 1);
    memset(&ag->inst_datas[call_index], 0, sizeof(ZirInstData));
    ag->inst_tags[call_index] = (ZirInstTag)0;
    ag->inst_len++;
    gzAppendInstruction(gz, call_index);

    // Process arguments in sub-blocks (AstGen.zig:10096-10116).
    // Upstream uses a separate scratch array; we use a local buffer for body
    // lengths and append body instructions to scratch_extra, then copy all
    // to extra after the call payload.
    uint32_t call_inst = call_index + ZIR_REF_START_INDEX;
    ResultLoc arg_rl = { .tag = RL_COERCED_TY,
        .data = call_inst,
        .src_node = 0,
        .ctx = RI_CTX_FN_ARG };

    // Use scratch_extra to collect body lengths + body instructions,
    // mirroring upstream's scratch array (AstGen.zig:10096-10116).
    uint32_t scratch_top = ag->scratch_extra_len;
    // Reserve space for cumulative body lengths (one per arg).
    ensureScratchExtraCapacity(ag, args_len);
    ag->scratch_extra_len += args_len;

    for (uint32_t i = 0; i < args_len; i++) {
        GenZir arg_block = makeSubBlock(gz, scope);
        uint32_t arg_ref
            = exprRl(&arg_block, &arg_block.base, arg_rl, args[i]);

        // break_inline with param_node src (AstGen.zig:10108).
        int32_t param_src
            = (int32_t)args[i] - (int32_t)arg_block.decl_node_index;
        makeBreakInline(&arg_block, call_index, arg_ref, param_src);

        // Append arg_block body to scratch_extra (with ref_table fixups).
        uint32_t raw_body_len = gzInstructionsLen(&arg_block);
        const uint32_t* body = gzInstructionsSlice(&arg_block);
        uint32_t fixup_len = countBodyLenAfterFixups(ag, body, raw_body_len);
        ensureScratchExtraCapacity(ag, fixup_len);
        for (uint32_t j = 0; j < raw_body_len; j++) {
            appendPossiblyRefdBodyInstScratch(ag, body[j]);
        }
        // Record cumulative body length (AstGen.zig:10114).
        ag->scratch_extra[scratch_top + i]
            = ag->scratch_extra_len - scratch_top;
        gzUnstack(&arg_block);
    }

    // Build call payload (AstGen.zig:10118-10168).
    // Upstream layout: [flags, callee/obj_ptr, field_name_start], then
    // body_lengths + body_instructions from scratch.
    // Flags layout (packed): modifier:u3, ensure_result_used:bool,
    // pop_error_return_trace:bool, args_len:u27.
    // pop_error_return_trace = !propagate_error_trace
    // (AstGen.zig:10121-10124).
    bool propagate_error_trace
        = (rl.ctx == RI_CTX_ERROR_HANDLING_EXPR || rl.ctx == RI_CTX_RETURN
            || rl.ctx == RI_CTX_FN_ARG || rl.ctx == RI_CTX_CONST_INIT);
    uint32_t flags = (propagate_error_trace ? 0u : (1u << 4))
        | ((args_len & 0x7FFFFFFu) << 5); // args_len

    if (callee.is_field) {
        // FieldCall: {flags, obj_ptr, field_name_start} (AstGen.zig:10148).
        ensureExtraCapacity(ag, 3 + (ag->scratch_extra_len - scratch_top));
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = flags;
        ag->extra[ag->extra_len++] = callee.obj_ptr;
        ag->extra[ag->extra_len++] = callee.field_name_start;
        // Append scratch data (body lengths + body instructions).
        if (args_len != 0) {
            memcpy(ag->extra + ag->extra_len, ag->scratch_extra + scratch_top,
                (ag->scratch_extra_len - scratch_top) * sizeof(uint32_t));
            ag->extra_len += ag->scratch_extra_len - scratch_top;
        }
        ag->inst_tags[call_index] = ZIR_INST_FIELD_CALL;
        ag->inst_datas[call_index].pl_node.src_node
            = (int32_t)node - (int32_t)gz->decl_node_index;
        ag->inst_datas[call_index].pl_node.payload_index = payload_index;
    } else {
        // Call: {flags, callee} (AstGen.zig:10128).
        ensureExtraCapacity(ag, 2 + (ag->scratch_extra_len - scratch_top));
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = flags;
        ag->extra[ag->extra_len++] = callee.direct;
        // Append scratch data (body lengths + body instructions).
        if (args_len != 0) {
            memcpy(ag->extra + ag->extra_len, ag->scratch_extra + scratch_top,
                (ag->scratch_extra_len - scratch_top) * sizeof(uint32_t));
            ag->extra_len += ag->scratch_extra_len - scratch_top;
        }
        ag->inst_tags[call_index] = ZIR_INST_CALL;
        ag->inst_datas[call_index].pl_node.src_node
            = (int32_t)node - (int32_t)gz->decl_node_index;
        ag->inst_datas[call_index].pl_node.payload_index = payload_index;
    }

    // Restore scratch (AstGen.zig:10097 defer).
    ag->scratch_extra_len = scratch_top;

    return call_index + ZIR_REF_START_INDEX;
}

// structInitExprAnon (AstGen.zig:1865-1893).
// Anonymous struct init using struct_init_anon instruction.
static uint32_t structInitExprAnon(GenZir* gz, Scope* scope, uint32_t node,
    const uint32_t* fields, uint32_t fields_len) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    ensureExtraCapacity(ag, 3 + fields_len * 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = node; // abs_node
    ag->extra[ag->extra_len++] = ag->source_line; // abs_line
    ag->extra[ag->extra_len++] = fields_len;
    uint32_t items_start = ag->extra_len;
    ag->extra_len += fields_len * 2;

    for (uint32_t i = 0; i < fields_len; i++) {
        uint32_t field_init = fields[i];
        uint32_t name_token = firstToken(tree, field_init) - 2;
        uint32_t str_index = identAsString(ag, name_token);
        uint32_t init_ref = expr(gz, scope, field_init);
        ag->extra[items_start + i * 2] = str_index;
        ag->extra[items_start + i * 2 + 1] = init_ref;
    }

    return addPlNodePayloadIndex(
        gz, ZIR_INST_STRUCT_INIT_ANON, node, payload_index);
}

// structInitExprTyped (AstGen.zig:1896-1931).
// Typed struct init using struct_init or struct_init_ref instruction.
static uint32_t structInitExprTyped(GenZir* gz, Scope* scope, uint32_t node,
    const uint32_t* fields, uint32_t fields_len, uint32_t ty_inst,
    bool is_ref) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    ensureExtraCapacity(ag, 3 + fields_len * 2);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = node; // abs_node
    ag->extra[ag->extra_len++] = ag->source_line; // abs_line
    ag->extra[ag->extra_len++] = fields_len;
    uint32_t items_start = ag->extra_len;
    ag->extra_len += fields_len * 2;

    for (uint32_t i = 0; i < fields_len; i++) {
        uint32_t field_init = fields[i];
        uint32_t name_token = firstToken(tree, field_init) - 2;
        uint32_t str_index = identAsString(ag, name_token);
        uint32_t field_ty_inst = addPlNodeBin(gz,
            ZIR_INST_STRUCT_INIT_FIELD_TYPE, field_init, ty_inst, str_index);
        ResultLoc elem_rl = { .tag = RL_COERCED_TY,
            .data = field_ty_inst,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t init_ref = exprRl(gz, scope, elem_rl, field_init);
        ag->extra[items_start + i * 2]
            = field_ty_inst - ZIR_REF_START_INDEX; // .toIndex()
        ag->extra[items_start + i * 2 + 1] = init_ref;
    }

    ZirInstTag init_tag
        = is_ref ? ZIR_INST_STRUCT_INIT_REF : ZIR_INST_STRUCT_INIT;
    return addPlNodePayloadIndex(gz, init_tag, node, payload_index);
}

// --- structInitExpr (AstGen.zig:1674) ---
static uint32_t structInitExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract type_expr and fields.
    uint32_t type_expr_node = 0; // 0 = anonymous (.{...})
    uint32_t field_buf[2];
    const uint32_t* fields = NULL;
    uint32_t fields_len = 0;

    switch (tag) {
    case AST_NODE_STRUCT_INIT_DOT_TWO:
    case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA: {
        // .{.a = lhs, .b = rhs}
        uint32_t idx = 0;
        if (nd.lhs != 0)
            field_buf[idx++] = nd.lhs;
        if (nd.rhs != 0)
            field_buf[idx++] = nd.rhs;
        fields = field_buf;
        fields_len = idx;
        break;
    }
    case AST_NODE_STRUCT_INIT_DOT:
    case AST_NODE_STRUCT_INIT_DOT_COMMA: {
        uint32_t start = nd.lhs;
        uint32_t end = nd.rhs;
        fields = tree->extra_data.arr + start;
        fields_len = end - start;
        break;
    }
    case AST_NODE_STRUCT_INIT_ONE:
    case AST_NODE_STRUCT_INIT_ONE_COMMA: {
        type_expr_node = nd.lhs;
        if (nd.rhs != 0) {
            field_buf[0] = nd.rhs;
            fields = field_buf;
            fields_len = 1;
        }
        break;
    }
    case AST_NODE_STRUCT_INIT:
    case AST_NODE_STRUCT_INIT_COMMA: {
        type_expr_node = nd.lhs;
        uint32_t extra_idx = nd.rhs;
        uint32_t range_start = tree->extra_data.arr[extra_idx];
        uint32_t range_end = tree->extra_data.arr[extra_idx + 1];
        fields = tree->extra_data.arr + range_start;
        fields_len = range_end - range_start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    if (type_expr_node == 0 && fields_len == 0) {
        // .{} — depends on result location (AstGen.zig:1687-1698).
        if (rl.tag == RL_REF_COERCED_TY) {
            return addUnNode(
                gz, ZIR_INST_STRUCT_INIT_EMPTY_REF_RESULT, rl.data, node);
        }
        if (rl.tag == RL_TY || rl.tag == RL_COERCED_TY) {
            return addUnNode(
                gz, ZIR_INST_STRUCT_INIT_EMPTY_RESULT, rl.data, node);
        }
        if (rl.tag == RL_DISCARD) {
            return ZIR_REF_VOID_VALUE;
        }
        if (rl.tag == RL_PTR) {
            // AstGen.zig:1691-1696.
            uint32_t ty_inst = rlResultType(gz, rl, node);
            uint32_t val = addUnNode(
                gz, ZIR_INST_STRUCT_INIT_EMPTY_RESULT, ty_inst, node);
            return rvalue(gz, rl, val, node);
        }
        // RL_NONE, RL_REF, RL_INFERRED_PTR (AstGen.zig:1697-1699).
        return rvalue(gz, rl, ZIR_REF_EMPTY_TUPLE, node);
    }

    // Pre-register all field names to match upstream string ordering.
    // Upstream has a duplicate name check (AstGen.zig:1756-1806) that
    // adds all field names to string_bytes before evaluating values.
    for (uint32_t i = 0; i < fields_len; i++) {
        uint32_t name_token = firstToken(tree, fields[i]) - 2;
        identAsString(ag, name_token);
    }

    if (type_expr_node == 0 && fields_len > 0) {
        // Anonymous struct init with fields (AstGen.zig:1821-1861).
        switch (rl.tag) {
        case RL_NONE:
            // structInitExprAnon (AstGen.zig:1822, 1865-1893).
            return structInitExprAnon(gz, scope, node, fields, fields_len);
        case RL_DISCARD: {
            // Even if discarding we must perform side-effects
            // (AstGen.zig:1823-1828).
            for (uint32_t i = 0; i < fields_len; i++)
                exprRl(gz, scope, RL_DISCARD_VAL, fields[i]);
            return ZIR_REF_VOID_VALUE;
        }
        case RL_REF: {
            // structInitExprAnon + ref (AstGen.zig:1830-1833).
            uint32_t result
                = structInitExprAnon(gz, scope, node, fields, fields_len);
            return addUnTok(gz, ZIR_INST_REF, result, firstToken(tree, node));
        }
        case RL_REF_COERCED_TY: {
            // Get elem type, validate, structInitExprTyped(is_ref=true)
            // (AstGen.zig:1834-1837).
            uint32_t result_ty_inst
                = addUnNode(gz, ZIR_INST_ELEM_TYPE, rl.data, node);
            addUnNode(gz, ZIR_INST_VALIDATE_STRUCT_INIT_RESULT_TY,
                result_ty_inst, node);
            return structInitExprTyped(
                gz, scope, node, fields, fields_len, result_ty_inst, true);
        }
        case RL_TY:
        case RL_COERCED_TY: {
            // validate_struct_init_result_ty +
            // structInitExprTyped(is_ref=false) (AstGen.zig:1839-1841).
            uint32_t ty_inst = rl.data;
            addUnNode(
                gz, ZIR_INST_VALIDATE_STRUCT_INIT_RESULT_TY, ty_inst, node);
            return structInitExprTyped(
                gz, scope, node, fields, fields_len, ty_inst, false);
        }
        case RL_PTR: {
            // structInitExprPtr (AstGen.zig:1843-1846, 1934-1964).
            uint32_t struct_ptr_inst
                = addUnNode(gz, ZIR_INST_OPT_EU_BASE_PTR_INIT, rl.data, node);
            // Block payload: body_len = fields_len.
            ensureExtraCapacity(ag, 1 + fields_len);
            uint32_t payload_index = ag->extra_len;
            ag->extra[ag->extra_len++] = fields_len;
            uint32_t items_start = ag->extra_len;
            ag->extra_len += fields_len;

            for (uint32_t i = 0; i < fields_len; i++) {
                uint32_t field_init = fields[i];
                uint32_t name_token = firstToken(tree, field_init) - 2;
                uint32_t str_index = identAsString(ag, name_token);
                // struct_init_field_ptr (AstGen.zig:1954-1957).
                uint32_t field_ptr
                    = addPlNodeBin(gz, ZIR_INST_STRUCT_INIT_FIELD_PTR,
                        field_init, struct_ptr_inst, str_index);
                ag->extra[items_start + i]
                    = field_ptr - ZIR_REF_START_INDEX; // .toIndex()
                // Evaluate init with ptr RL (AstGen.zig:1960).
                ResultLoc ptr_rl = { .tag = RL_PTR,
                    .data = field_ptr,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                exprRl(gz, scope, ptr_rl, field_init);
            }
            addPlNodePayloadIndex(
                gz, ZIR_INST_VALIDATE_PTR_STRUCT_INIT, node, payload_index);
            return ZIR_REF_VOID_VALUE;
        }
        case RL_INFERRED_PTR: {
            // Standard anon init + rvalue store (AstGen.zig:1847-1852).
            uint32_t struct_inst
                = structInitExprAnon(gz, scope, node, fields, fields_len);
            return rvalue(gz, rl, struct_inst, node);
        }
        case RL_DESTRUCTURE:
            // Struct value cannot be destructured (AstGen.zig:1854-1859).
            SET_ERROR(ag);
            return ZIR_REF_VOID_VALUE;
        }
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Typed init: evaluate type, emit struct_init_empty or struct_init.
    if (type_expr_node != 0 && fields_len == 0) {
        // Check for [_]T{} pattern (AstGen.zig:1707-1753).
        AstNodeTag type_tag = tree->nodes.tags[type_expr_node];
        if (type_tag == AST_NODE_ARRAY_TYPE
            || type_tag == AST_NODE_ARRAY_TYPE_SENTINEL) {
            AstData type_nd = tree->nodes.datas[type_expr_node];
            uint32_t elem_count_node = type_nd.lhs;
            if (tree->nodes.tags[elem_count_node] == AST_NODE_IDENTIFIER
                && isUnderscoreIdent(tree, elem_count_node)) {
                // Inferred length with 0 fields → length 0.
                if (type_tag == AST_NODE_ARRAY_TYPE) {
                    uint32_t elem_type = typeExpr(gz, scope, type_nd.rhs);
                    uint32_t array_type_inst
                        = addPlNodeBin(gz, ZIR_INST_ARRAY_TYPE, type_expr_node,
                            ZIR_REF_ZERO_USIZE, elem_type);
                    return rvalue(gz, rl,
                        addUnNode(gz, ZIR_INST_STRUCT_INIT_EMPTY,
                            array_type_inst, node),
                        node);
                }
                // ARRAY_TYPE_SENTINEL: extra[rhs] = sentinel, extra[rhs+1]
                // = elem_type
                uint32_t sentinel_node = tree->extra_data.arr[type_nd.rhs];
                uint32_t elem_type_node
                    = tree->extra_data.arr[type_nd.rhs + 1];
                uint32_t elem_type = typeExpr(gz, scope, elem_type_node);
                ResultLoc sent_rl = { .tag = RL_TY,
                    .data = elem_type,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                uint32_t sentinel = comptimeExpr(gz, scope, sent_rl,
                    sentinel_node, COMPTIME_REASON_ARRAY_SENTINEL);
                uint32_t array_type_inst = addPlNodeTriple(gz,
                    ZIR_INST_ARRAY_TYPE_SENTINEL, type_expr_node,
                    ZIR_REF_ZERO_USIZE, elem_type, sentinel);
                return rvalue(gz, rl,
                    addUnNode(
                        gz, ZIR_INST_STRUCT_INIT_EMPTY, array_type_inst, node),
                    node);
            }
        }
        uint32_t ty_inst = typeExpr(gz, scope, type_expr_node);
        return rvalue(gz, rl,
            addUnNode(gz, ZIR_INST_STRUCT_INIT_EMPTY, ty_inst, node), node);
    }

    // Typed struct init with fields (AstGen.zig:1808-1818).
    if (type_expr_node != 0 && fields_len > 0) {
        uint32_t ty_inst = typeExpr(gz, scope, type_expr_node);
        addUnNode(gz, ZIR_INST_VALIDATE_STRUCT_INIT_TY, ty_inst, node);
        // Upstream: .ref => structInitExprTyped(is_ref=true)
        //           else => rvalue(structInitExprTyped(is_ref=false))
        if (rl.tag == RL_REF) {
            return structInitExprTyped(
                gz, scope, node, fields, fields_len, ty_inst, true);
        }
        uint32_t struct_inst = structInitExprTyped(
            gz, scope, node, fields, fields_len, ty_inst, false);
        return rvalue(gz, rl, struct_inst, node);
    }

    SET_ERROR(ag);
    return ZIR_REF_VOID_VALUE;
}

// --- tryExpr (AstGen.zig:5957) ---
static uint32_t tryExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    AstData nd = ag->tree->nodes.datas[node];
    uint32_t operand_node = nd.lhs;

    if (!gz->is_comptime) {
        emitDbgNode(gz, node);
    }
    uint32_t try_lc_line = ag->source_line - gz->decl_line;
    uint32_t try_lc_column = ag->source_column;

    // Determine operand rl and block tag based on result location
    // (AstGen.zig:5989-5992).
    ResultLoc operand_rl;
    ZirInstTag block_tag;
    ZirInstTag err_tag;
    if (RL_IS_REF(rl)) {
        operand_rl = RL_REF_VAL;
        block_tag = ZIR_INST_TRY_PTR;
        err_tag = ZIR_INST_ERR_UNION_CODE_PTR;
    } else {
        operand_rl = RL_NONE_VAL;
        block_tag = ZIR_INST_TRY;
        err_tag = ZIR_INST_ERR_UNION_CODE;
    }
    operand_rl.ctx = RI_CTX_ERROR_HANDLING_EXPR;

    // Evaluate operand (AstGen.zig:5993-6006).
    uint32_t operand = exprRl(gz, scope, operand_rl, operand_node);

    // Create try block instruction (AstGen.zig:6008).
    uint32_t try_inst = makeBlockInst(ag, block_tag, gz, node);
    gzAppendInstruction(gz, try_inst);

    // Else scope: extract error code, return it (AstGen.zig:6011-6025).
    GenZir else_scope = makeSubBlock(gz, scope);

    uint32_t err_code = addUnNode(&else_scope, err_tag, operand, node);

    // Emit defers for error path (AstGen.zig:6019).
    if (ag->fn_block != NULL) {
        const Scope* fn_block_scope = &((GenZir*)ag->fn_block)->base;
        genDefers(&else_scope, fn_block_scope, scope, DEFER_BOTH_SANS_ERR);
    }

    // Emit dbg_stmt at try keyword for error return tracing (AstGen.zig:6020).
    emitDbgStmt(&else_scope, try_lc_line, try_lc_column);

    // ret_node with error code (AstGen.zig:6021).
    addUnNode(&else_scope, ZIR_INST_RET_NODE, err_code, node);

    setTryBody(ag, &else_scope, try_inst, operand);
    // else_scope unstacked by setTryBody.

    // For ref/ref_coerced_ty, return directly; otherwise rvalue
    // (AstGen.zig:6025-6028).
    uint32_t result = try_inst + ZIR_REF_START_INDEX; // toRef()
    if (RL_IS_REF(rl))
        return result;
    return rvalue(gz, rl, result, node);
}

// --- boolBinOp (AstGen.zig:6274) ---
// Short-circuiting boolean and/or.

static uint32_t boolBinOp(
    GenZir* gz, Scope* scope, uint32_t node, ZirInstTag zir_tag) {
    AstGenCtx* ag = gz->astgen;
    AstData nd = ag->tree->nodes.datas[node];
    uint32_t lhs_node = nd.lhs;
    uint32_t rhs_node = nd.rhs;

    // Evaluate LHS (AstGen.zig:6285).
    uint32_t lhs = expr(gz, scope, lhs_node);

    // Reserve the bool_br instruction (payload set later)
    // (AstGen.zig:6286).
    uint32_t bool_br = reserveInstructionIndex(ag);
    gzAppendInstruction(gz, bool_br);

    // Evaluate RHS in sub-block (AstGen.zig:6288-6293).
    GenZir rhs_scope = makeSubBlock(gz, scope);
    uint32_t rhs = expr(&rhs_scope, &rhs_scope.base, rhs_node);

    if (!ag->has_compile_errors) {
        // break_inline from rhs to bool_br (AstGen.zig:6292).
        makeBreakInline(&rhs_scope, bool_br, rhs,
            (int32_t)rhs_node - (int32_t)rhs_scope.decl_node_index);
    }

    // setBoolBrBody (AstGen.zig:6294, 11929-11944).
    uint32_t raw_body_len = gzInstructionsLen(&rhs_scope);
    const uint32_t* body = gzInstructionsSlice(&rhs_scope);
    uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_body_len);
    ensureExtraCapacity(ag, 2 + body_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = lhs; // BoolBr.lhs
    ag->extra[ag->extra_len++] = body_len; // BoolBr.body_len
    for (uint32_t i = 0; i < raw_body_len; i++)
        appendPossiblyRefdBodyInst(ag, body[i]);
    gzUnstack(&rhs_scope);

    // Fill in the bool_br instruction.
    ag->inst_tags[bool_br] = zir_tag;
    ag->inst_datas[bool_br].pl_node.src_node
        = (int32_t)node - (int32_t)gz->decl_node_index;
    ag->inst_datas[bool_br].pl_node.payload_index = payload_index;

    return bool_br + ZIR_REF_START_INDEX;
}

// Mirrors nodeIsTriviallyZero (AstGen.zig:10299-10313).
static bool nodeIsTriviallyZero(const Ast* tree, uint32_t node) {
    if (tree->nodes.tags[node] != AST_NODE_NUMBER_LITERAL)
        return false;
    uint32_t tok = tree->nodes.main_tokens[node];
    uint32_t tok_start = tree->tokens.starts[tok];
    const char* source = (const char*)tree->source;
    if (source[tok_start] != '0')
        return false;
    // Distinguish "0.." (range, token is "0") from "0.5" (float literal).
    char c = source[tok_start + 1];
    if (c == '.')
        return source[tok_start + 2] == '.';
    // Any alphanumeric or underscore means the token is longer than "0".
    if (c >= '0' && c <= '9')
        return false;
    if (c >= 'a' && c <= 'z')
        return false;
    if (c >= 'A' && c <= 'Z')
        return false;
    if (c == '_')
        return false;
    return true;
}

// Mirrors expr (AstGen.zig:634) — main expression dispatcher.
static uint32_t exprRl(GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    if (node == 0) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }
    AstNodeTag tag = ag->tree->nodes.tags[node];
    AstData nd = ag->tree->nodes.datas[node];

    switch (tag) {
    case AST_NODE_NUMBER_LITERAL:
        return rvalue(
            gz, rl, numberLiteral(gz, node, node, NUM_SIGN_POSITIVE), node);
    case AST_NODE_BUILTIN_CALL_TWO:
    case AST_NODE_BUILTIN_CALL_TWO_COMMA:
        return builtinCall(gz, scope, rl, node);
    case AST_NODE_BUILTIN_CALL:
    case AST_NODE_BUILTIN_CALL_COMMA:
        return builtinCallMultiArg(gz, scope, rl, node, nd.lhs, nd.rhs);
    case AST_NODE_FIELD_ACCESS:
        return fieldAccessExpr(gz, scope, rl, node);
    case AST_NODE_IDENTIFIER:
        return identifierExpr(gz, scope, rl, node);
    case AST_NODE_STRING_LITERAL: {
        // Mirrors stringLiteral (AstGen.zig:8626).
        uint32_t str_lit_token = ag->tree->nodes.main_tokens[node];
        uint32_t str_index, str_len;
        strLitAsString(ag, str_lit_token, &str_index, &str_len);
        ZirInstData data;
        data.str.start = str_index;
        data.str.len = str_len;
        uint32_t str_result = addInstruction(gz, ZIR_INST_STR, data);
        return rvalue(gz, rl, str_result, node);
    }
    // address_of (AstGen.zig:953-960): evaluate operand with .ref rl.
    case AST_NODE_ADDRESS_OF: {
        uint32_t operand_node = ag->tree->nodes.datas[node].lhs;
        // Check for result type to emit validate_ref_ty (AstGen.zig:954-956).
        uint32_t res_ty = rlResultType(gz, rl, node);
        ResultLoc operand_rl;
        if (res_ty != 0) {
            addUnTok(gz, ZIR_INST_VALIDATE_REF_TY, res_ty,
                firstToken(ag->tree, node));
            // Pass ref_coerced_ty so init expressions can use the type
            // (AstGen.zig:958).
            operand_rl = (ResultLoc) {
                .tag = RL_REF_COERCED_TY, .data = res_ty, .src_node = 0
            };
        } else {
            operand_rl = RL_REF_VAL;
        }
        uint32_t result = exprRl(gz, scope, operand_rl, operand_node);
        return rvalue(gz, rl, result, node);
    }
    // ptr_type (AstGen.zig:1077-1081).
    case AST_NODE_PTR_TYPE_ALIGNED:
    case AST_NODE_PTR_TYPE_SENTINEL:
    case AST_NODE_PTR_TYPE:
    case AST_NODE_PTR_TYPE_BIT_RANGE:
        return rvalue(gz, rl, ptrTypeExpr(gz, scope, node), node);
    // array_type (AstGen.zig:940).
    case AST_NODE_ARRAY_TYPE:
        return rvalue(gz, rl, arrayTypeExpr(gz, scope, node), node);
    // array_init variants (AstGen.zig:836-856).
    case AST_NODE_ARRAY_INIT:
    case AST_NODE_ARRAY_INIT_COMMA:
    case AST_NODE_ARRAY_INIT_ONE:
    case AST_NODE_ARRAY_INIT_ONE_COMMA:
        return arrayInitExpr(gz, scope, rl, node);
    // array_cat (AstGen.zig:772): ++ binary operator.
    case AST_NODE_ARRAY_CAT:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_ARRAY_CAT), node);
    // array_mult (AstGen.zig:774-785): ** binary operator.
    case AST_NODE_ARRAY_MULT: {
        uint32_t res_ty = rlResultType(gz, rl, node);
        uint32_t lhs = exprRl(gz, scope, RL_NONE_VAL, nd.lhs);
        ResultLoc rhs_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_USIZE_TYPE,
            .src_node = 0,
            .ctx = 0 };
        uint32_t rhs = comptimeExpr(
            gz, scope, rhs_rl, nd.rhs, COMPTIME_REASON_ARRAY_MUL_FACTOR);
        uint32_t result = addPlNodeTriple(gz, ZIR_INST_ARRAY_MUL, node,
            res_ty != 0 ? res_ty : ZIR_REF_NONE, lhs, rhs);
        return rvalue(gz, rl, result, node);
    }
    // grouped_expression (AstGen.zig:1100): passthrough.
    case AST_NODE_GROUPED_EXPRESSION:
        return exprRl(gz, scope, rl, ag->tree->nodes.datas[node].lhs);
    // unreachable_literal (AstGen.zig:846-854).
    case AST_NODE_UNREACHABLE_LITERAL: {
        emitDbgNode(gz, node);
        ZirInstData udata;
        memset(&udata, 0, sizeof(udata));
        udata.unreachable_data.src_node
            = (int32_t)node - (int32_t)gz->decl_node_index;
        addInstruction(gz, ZIR_INST_UNREACHABLE, udata);
        return ZIR_REF_UNREACHABLE_VALUE;
    }
    // enum_literal (AstGen.zig:993).
    case AST_NODE_ENUM_LITERAL: {
        uint32_t ident_token = ag->tree->nodes.main_tokens[node];
        uint32_t str_index = identAsString(ag, ident_token);
        // If result type available, emit decl_literal (AstGen.zig:993-1003).
        uint32_t res_ty = rlResultType(gz, rl, node);
        if (res_ty != 0) {
            uint32_t res = addPlNodeBin(
                gz, ZIR_INST_DECL_LITERAL, node, res_ty, str_index);
            // decl_literal does the coercion for us (AstGen.zig:1001).
            // Only need rvalue for ptr/inferred_ptr/ref_coerced_ty.
            if (rl.tag == RL_TY || rl.tag == RL_COERCED_TY)
                return res;
            return rvalue(gz, rl, res, node);
        }
        return rvalue(gz, rl,
            addStrTok(gz, ZIR_INST_ENUM_LITERAL, str_index, ident_token),
            node);
    }
    // multiline_string_literal (AstGen.zig:8645).
    case AST_NODE_MULTILINE_STRING_LITERAL:
        return rvalue(gz, rl, multilineStringLiteral(gz, scope, node), node);
    // return (AstGen.zig:856).
    case AST_NODE_RETURN:
        return retExpr(gz, scope, node);
    // call (AstGen.zig:783-790).
    case AST_NODE_CALL_ONE:
    case AST_NODE_CALL_ONE_COMMA:
    case AST_NODE_CALL:
    case AST_NODE_CALL_COMMA:
        return rvalue(gz, rl, callExpr(gz, scope, rl, node), node);
    // struct_init (AstGen.zig:836-839).
    case AST_NODE_STRUCT_INIT_DOT_TWO:
    case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA:
    case AST_NODE_STRUCT_INIT_DOT:
    case AST_NODE_STRUCT_INIT_DOT_COMMA:
    case AST_NODE_STRUCT_INIT_ONE:
    case AST_NODE_STRUCT_INIT_ONE_COMMA:
    case AST_NODE_STRUCT_INIT:
    case AST_NODE_STRUCT_INIT_COMMA:
        return structInitExpr(gz, scope, rl, node);
    // container_decl (AstGen.zig:1083-1098).
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING:
        return rvalue(
            gz, rl, containerDecl(gz, scope, node, 2 /* anon */), node);
    // try (AstGen.zig:1115).
    case AST_NODE_TRY:
        return tryExpr(gz, scope, rl, node);
    // Comparison operators (AstGen.zig:714-726).
    case AST_NODE_EQUAL_EQUAL:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_EQ), node);
    case AST_NODE_BANG_EQUAL:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_NEQ), node);
    case AST_NODE_LESS_THAN:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_LT), node);
    case AST_NODE_GREATER_THAN:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_GT), node);
    case AST_NODE_LESS_OR_EQUAL:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_LTE), node);
    case AST_NODE_GREATER_OR_EQUAL:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_CMP_GTE), node);
    // Arithmetic (AstGen.zig:656-698).
    case AST_NODE_ADD:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_ADD), node);
    case AST_NODE_SUB:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_SUB), node);
    case AST_NODE_MUL:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_MUL), node);
    case AST_NODE_DIV:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_DIV), node);
    case AST_NODE_MOD:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_MOD), node);
    // Bitwise (AstGen.zig:700-712).
    case AST_NODE_BIT_AND:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_BIT_AND), node);
    case AST_NODE_BIT_OR:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_BIT_OR), node);
    case AST_NODE_BIT_XOR:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_XOR), node);
    case AST_NODE_SHL:
        return rvalue(gz, rl, shiftOp(gz, scope, node, ZIR_INST_SHL), node);
    case AST_NODE_SHR:
        return rvalue(gz, rl, shiftOp(gz, scope, node, ZIR_INST_SHR), node);
    // Boolean operators (AstGen.zig:728-731) — special: boolBinOp.
    case AST_NODE_BOOL_AND:
        return rvalue(
            gz, rl, boolBinOp(gz, scope, node, ZIR_INST_BOOL_BR_AND), node);
    case AST_NODE_BOOL_OR:
        return rvalue(
            gz, rl, boolBinOp(gz, scope, node, ZIR_INST_BOOL_BR_OR), node);
    // Unary operators (AstGen.zig:919-938).
    case AST_NODE_BOOL_NOT:
        return rvalue(gz, rl,
            addUnNode(gz, ZIR_INST_BOOL_NOT, expr(gz, scope, nd.lhs), node),
            node);
    case AST_NODE_BIT_NOT:
        return rvalue(gz, rl,
            addUnNode(gz, ZIR_INST_BIT_NOT, expr(gz, scope, nd.lhs), node),
            node);
    // negation (AstGen.zig:9863-9882).
    case AST_NODE_NEGATION: {
        // Check for number_literal as sub-expression to preserve negativity
        // (AstGen.zig:9875-9877).
        if (ag->tree->nodes.tags[nd.lhs] == AST_NODE_NUMBER_LITERAL) {
            return rvalue(gz, rl,
                numberLiteral(gz, nd.lhs, node, NUM_SIGN_NEGATIVE), node);
        }
        return rvalue(gz, rl,
            addUnNode(gz, ZIR_INST_NEGATE, expr(gz, scope, nd.lhs), node),
            node);
    }
    case AST_NODE_NEGATION_WRAP:
        return rvalue(gz, rl,
            addUnNode(gz, ZIR_INST_NEGATE_WRAP, expr(gz, scope, nd.lhs), node),
            node);
    // deref (AstGen.zig:942-951).
    case AST_NODE_DEREF: {
        uint32_t lhs = expr(gz, scope, nd.lhs);
        addUnNode(gz, ZIR_INST_VALIDATE_DEREF, lhs, node);
        if (RL_IS_REF(rl))
            return lhs;
        return rvalue(gz, rl, addUnNode(gz, ZIR_INST_LOAD, lhs, node), node);
    }
    // optional_type (AstGen.zig:961-964).
    case AST_NODE_OPTIONAL_TYPE:
        return rvalue(gz, rl,
            addUnNode(
                gz, ZIR_INST_OPTIONAL_TYPE, typeExpr(gz, scope, nd.lhs), node),
            node);
    // unwrap_optional (AstGen.zig:966-983).
    case AST_NODE_UNWRAP_OPTIONAL: {
        if (RL_IS_REF(rl)) {
            uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
            advanceSourceCursorToMainToken(ag, gz, node);
            uint32_t saved_line = ag->source_line - gz->decl_line;
            uint32_t saved_col = ag->source_column;
            emitDbgStmt(gz, saved_line, saved_col);
            return addUnNode(
                gz, ZIR_INST_OPTIONAL_PAYLOAD_SAFE_PTR, lhs, node);
        } else {
            uint32_t lhs = expr(gz, scope, nd.lhs);
            advanceSourceCursorToMainToken(ag, gz, node);
            uint32_t saved_line = ag->source_line - gz->decl_line;
            uint32_t saved_col = ag->source_column;
            emitDbgStmt(gz, saved_line, saved_col);
            return rvalue(gz, rl,
                addUnNode(gz, ZIR_INST_OPTIONAL_PAYLOAD_SAFE, lhs, node),
                node);
        }
    }
    // error_union type (AstGen.zig:788-797).
    case AST_NODE_ERROR_UNION: {
        uint32_t lhs = typeExpr(gz, scope, nd.lhs);
        uint32_t rhs = typeExpr(gz, scope, nd.rhs);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_ERROR_UNION_TYPE, node, lhs, rhs), node);
    }
    // char_literal (AstGen.zig:8662-8675).
    case AST_NODE_CHAR_LITERAL: {
        uint32_t main_tok = ag->tree->nodes.main_tokens[node];
        uint32_t tok_start = ag->tree->tokens.starts[main_tok];
        const char* src = ag->tree->source;
        uint32_t ci = tok_start + 1; // skip opening quote
        uint64_t char_val;
        if (src[ci] == '\\') {
            // Escape sequence (AstGen.zig:8668-8675).
            ci++;
            switch (src[ci]) {
            case 'n':
                char_val = '\n';
                break;
            case 'r':
                char_val = '\r';
                break;
            case 't':
                char_val = '\t';
                break;
            case '\\':
                char_val = '\\';
                break;
            case '\'':
                char_val = '\'';
                break;
            case '"':
                char_val = '"';
                break;
            case 'x': {
                // \xNN hex escape.
                uint8_t val = 0;
                for (int k = 0; k < 2; k++) {
                    ci++;
                    char c = src[ci];
                    if (c >= '0' && c <= '9')
                        val = (uint8_t)(val * 16 + (uint8_t)(c - '0'));
                    else if (c >= 'a' && c <= 'f')
                        val = (uint8_t)(val * 16 + 10 + (uint8_t)(c - 'a'));
                    else if (c >= 'A' && c <= 'F')
                        val = (uint8_t)(val * 16 + 10 + (uint8_t)(c - 'A'));
                }
                char_val = val;
                break;
            }
            case 'u': {
                // \u{NNNNNN} unicode escape (string_literal.zig:194-231).
                // Skip past '{'.
                ci++;
                uint32_t codepoint = 0;
                while (true) {
                    ci++;
                    char c = src[ci];
                    if (c >= '0' && c <= '9')
                        codepoint = codepoint * 16 + (uint32_t)(c - '0');
                    else if (c >= 'a' && c <= 'f')
                        codepoint = codepoint * 16 + 10 + (uint32_t)(c - 'a');
                    else if (c >= 'A' && c <= 'F')
                        codepoint = codepoint * 16 + 10 + (uint32_t)(c - 'A');
                    else
                        break; // Must be '}'.
                }
                char_val = codepoint;
                break;
            }
            default:
                char_val = (uint8_t)src[ci];
                break;
            }
        } else {
            char_val = (uint64_t)(uint8_t)src[ci];
        }
        return rvalue(gz, rl, addInt(gz, char_val), node);
    }
    // arrayAccess (AstGen.zig:6192-6221).
    case AST_NODE_ARRAY_ACCESS: {
        if (RL_IS_REF(rl)) {
            uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
            advanceSourceCursorToMainToken(ag, gz, node);
            uint32_t saved_line = ag->source_line - gz->decl_line;
            uint32_t saved_col = ag->source_column;
            uint32_t rhs = expr(gz, scope, nd.rhs);
            emitDbgStmt(gz, saved_line, saved_col);
            return addPlNodeBin(gz, ZIR_INST_ELEM_PTR_NODE, node, lhs, rhs);
        }
        uint32_t lhs = expr(gz, scope, nd.lhs);
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        uint32_t rhs = expr(gz, scope, nd.rhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_ELEM_VAL_NODE, node, lhs, rhs), node);
    }
    // slice (AstGen.zig:882-939).
    case AST_NODE_SLICE_OPEN: {
        // (AstGen.zig:908-937).
        uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        ResultLoc usize_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_USIZE_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t start = exprRl(gz, scope, usize_rl, nd.rhs);
        emitDbgStmt(gz, saved_line, saved_col);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_SLICE_START, node, lhs, start), node);
    }
    case AST_NODE_SLICE: {
        // Slice[rhs]: { start, end } (AstGen.zig:882-937).
        const Ast* stree = ag->tree;
        uint32_t start_node = stree->extra_data.arr[nd.rhs];
        uint32_t end_node = stree->extra_data.arr[nd.rhs + 1];
        // slice_length optimization (AstGen.zig:887-906).
        if (stree->nodes.tags[nd.lhs] == AST_NODE_SLICE_OPEN
            && nodeIsTriviallyZero(stree, start_node)) {
            AstData inner_nd = stree->nodes.datas[nd.lhs];
            uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, inner_nd.lhs);
            ResultLoc usize_rl = { .tag = RL_COERCED_TY,
                .data = ZIR_REF_USIZE_TYPE,
                .src_node = 0,
                .ctx = RI_CTX_NONE,
                .components = NULL,
                .components_len = 0 };
            uint32_t start_ref = exprRl(gz, scope, usize_rl, inner_nd.rhs);
            advanceSourceCursorToMainToken(ag, gz, node);
            uint32_t saved_line = ag->source_line - gz->decl_line;
            uint32_t saved_col = ag->source_column;
            uint32_t len_ref = exprRl(gz, scope, usize_rl, end_node);
            emitDbgStmt(gz, saved_line, saved_col);
            ensureExtraCapacity(ag, 5);
            uint32_t payload_index = ag->extra_len;
            ag->extra[ag->extra_len++] = lhs;
            ag->extra[ag->extra_len++] = start_ref;
            ag->extra[ag->extra_len++] = len_ref;
            ag->extra[ag->extra_len++] = ZIR_REF_NONE; // no sentinel
            int32_t src_off = (int32_t)nd.lhs - (int32_t)gz->decl_node_index;
            memcpy(&ag->extra[ag->extra_len], &src_off, sizeof(uint32_t));
            ag->extra_len++;
            ZirInstData data;
            data.pl_node.src_node
                = (int32_t)node - (int32_t)gz->decl_node_index;
            data.pl_node.payload_index = payload_index;
            return rvalue(
                gz, rl, addInstruction(gz, ZIR_INST_SLICE_LENGTH, data), node);
        }
        // Normal path.
        uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        ResultLoc usize_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_USIZE_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
            .components = NULL,
            .components_len = 0 };
        uint32_t start_ref = exprRl(gz, scope, usize_rl, start_node);
        uint32_t end_ref = exprRl(gz, scope, usize_rl, end_node);
        emitDbgStmt(gz, saved_line, saved_col);
        ensureExtraCapacity(ag, 3);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = start_ref;
        ag->extra[ag->extra_len++] = end_ref;
        ZirInstData data;
        data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        data.pl_node.payload_index = payload_index;
        return rvalue(
            gz, rl, addInstruction(gz, ZIR_INST_SLICE_END, data), node);
    }
    case AST_NODE_SLICE_SENTINEL: {
        // SliceSentinel[rhs]: { start, end, sentinel }
        // (AstGen.zig:882-937).
        const Ast* stree = ag->tree;
        uint32_t start_node = stree->extra_data.arr[nd.rhs];
        uint32_t end_node = stree->extra_data.arr[nd.rhs + 1];
        uint32_t sentinel_node = stree->extra_data.arr[nd.rhs + 2];
        // slice_length optimization (AstGen.zig:887-906).
        if (end_node != 0 && stree->nodes.tags[nd.lhs] == AST_NODE_SLICE_OPEN
            && nodeIsTriviallyZero(stree, start_node)) {
            AstData inner_nd = stree->nodes.datas[nd.lhs];
            uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, inner_nd.lhs);
            ResultLoc usize_rl = { .tag = RL_COERCED_TY,
                .data = ZIR_REF_USIZE_TYPE,
                .src_node = 0,
                .ctx = RI_CTX_NONE,
                .components = NULL,
                .components_len = 0 };
            uint32_t start_ref = exprRl(gz, scope, usize_rl, inner_nd.rhs);
            advanceSourceCursorToMainToken(ag, gz, node);
            uint32_t saved_line = ag->source_line - gz->decl_line;
            uint32_t saved_col = ag->source_column;
            uint32_t len_ref = exprRl(gz, scope, usize_rl, end_node);
            uint32_t sentinel_ref
                = exprRl(gz, scope, RL_NONE_VAL, sentinel_node);
            emitDbgStmt(gz, saved_line, saved_col);
            ensureExtraCapacity(ag, 5);
            uint32_t payload_index = ag->extra_len;
            ag->extra[ag->extra_len++] = lhs;
            ag->extra[ag->extra_len++] = start_ref;
            ag->extra[ag->extra_len++] = len_ref;
            ag->extra[ag->extra_len++] = sentinel_ref;
            int32_t src_off = (int32_t)nd.lhs - (int32_t)gz->decl_node_index;
            memcpy(&ag->extra[ag->extra_len], &src_off, sizeof(uint32_t));
            ag->extra_len++;
            ZirInstData data;
            data.pl_node.src_node
                = (int32_t)node - (int32_t)gz->decl_node_index;
            data.pl_node.payload_index = payload_index;
            return rvalue(
                gz, rl, addInstruction(gz, ZIR_INST_SLICE_LENGTH, data), node);
        }
        // Normal path.
        uint32_t lhs = exprRl(gz, scope, RL_REF_VAL, nd.lhs);
        advanceSourceCursorToMainToken(ag, gz, node);
        uint32_t saved_line = ag->source_line - gz->decl_line;
        uint32_t saved_col = ag->source_column;
        // start/end coerced to usize (AstGen.zig:911-912).
        ResultLoc usize_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_USIZE_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
            .components = NULL,
            .components_len = 0 };
        uint32_t start_ref = exprRl(gz, scope, usize_rl, start_node);
        uint32_t end_ref = (end_node != 0)
            ? exprRl(gz, scope, usize_rl, end_node)
            : ZIR_REF_NONE;
        // sentinel: create slice_sentinel_ty and coerce (AstGen.zig:913-916).
        uint32_t sentinel_ty
            = addUnNode(gz, ZIR_INST_SLICE_SENTINEL_TY, lhs, node);
        ResultLoc sent_rl = { .tag = RL_COERCED_TY,
            .data = sentinel_ty,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
            .components = NULL,
            .components_len = 0 };
        uint32_t sentinel_ref = exprRl(gz, scope, sent_rl, sentinel_node);
        emitDbgStmt(gz, saved_line, saved_col);
        ensureExtraCapacity(ag, 4);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = lhs;
        ag->extra[ag->extra_len++] = start_ref;
        ag->extra[ag->extra_len++] = end_ref;
        ag->extra[ag->extra_len++] = sentinel_ref;
        ZirInstData data;
        data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        data.pl_node.payload_index = payload_index;
        return rvalue(
            gz, rl, addInstruction(gz, ZIR_INST_SLICE_SENTINEL, data), node);
    }
    // orelse (AstGen.zig:1054-1075).
    case AST_NODE_ORELSE:
        if (RL_IS_REF(rl)) {
            return orelseCatchExpr(gz, scope, rl, node,
                ZIR_INST_IS_NON_NULL_PTR, ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE_PTR,
                (ZirInstTag)0, UINT32_MAX);
        } else {
            return orelseCatchExpr(gz, scope, rl, node, ZIR_INST_IS_NON_NULL,
                ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE, (ZirInstTag)0, UINT32_MAX);
        }
    // catch (AstGen.zig:1017-1052).
    case AST_NODE_CATCH: {
        uint32_t catch_token = ag->tree->nodes.main_tokens[node];
        uint32_t pt = (ag->tree->tokens.tags[catch_token + 1] == TOKEN_PIPE)
            ? catch_token + 2
            : UINT32_MAX;
        // Detect catch |err| switch(err) { ... } pattern
        // (AstGen.zig:1023-1029).
        if (pt != UINT32_MAX) {
            AstData catch_data = ag->tree->nodes.datas[node];
            uint32_t rhs = catch_data.rhs;
            AstNodeTag rhs_tag = ag->tree->nodes.tags[rhs];
            if ((rhs_tag == AST_NODE_SWITCH
                    || rhs_tag == AST_NODE_SWITCH_COMMA)
                && ag->tree->tokens.tags[ag->tree->nodes.main_tokens[rhs]]
                    == TOKEN_KEYWORD_SWITCH) {
                // Check switch condition is identifier matching capture.
                uint32_t cond = ag->tree->nodes.datas[rhs].lhs;
                if (ag->tree->nodes.tags[cond] == AST_NODE_IDENTIFIER
                    && tokenIdentEql(
                        ag->tree, pt, ag->tree->nodes.main_tokens[cond])) {
                    // Apply ri.br(): convert coerced_ty to ty.
                    ResultLoc brl = rl;
                    if (brl.tag == RL_COERCED_TY)
                        brl.tag = RL_TY;
                    return switchExprErrUnion(gz, scope, brl, node, 0);
                }
            }
        }
        if (RL_IS_REF(rl)) {
            return orelseCatchExpr(gz, scope, rl, node,
                ZIR_INST_IS_NON_ERR_PTR, ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE_PTR,
                ZIR_INST_ERR_UNION_CODE_PTR, pt);
        } else {
            return orelseCatchExpr(gz, scope, rl, node, ZIR_INST_IS_NON_ERR,
                ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE, ZIR_INST_ERR_UNION_CODE,
                pt);
        }
    }
    // Block expressions (AstGen.zig:984-992).
    case AST_NODE_BLOCK_TWO:
    case AST_NODE_BLOCK_TWO_SEMICOLON:
    case AST_NODE_BLOCK:
    case AST_NODE_BLOCK_SEMICOLON:
        return blockExprExpr(gz, scope, rl, node);
    // Anonymous array init (AstGen.zig:1119-1127).
    case AST_NODE_ARRAY_INIT_DOT_TWO:
    case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA:
    case AST_NODE_ARRAY_INIT_DOT:
    case AST_NODE_ARRAY_INIT_DOT_COMMA:
        return arrayInitDotExpr(gz, scope, rl, node);
    // if (AstGen.zig:1013-1024).
    case AST_NODE_IF_SIMPLE:
    case AST_NODE_IF: {
        // Detect switchExprErrUnion pattern: if (x) |v| { ... } else |err|
        // switch (err) { ... } (AstGen.zig:862-871).
        if (tag == AST_NODE_IF) {
            uint32_t then_node_if = ag->tree->extra_data.arr[nd.rhs];
            uint32_t else_node_if = ag->tree->extra_data.arr[nd.rhs + 1];
            if (else_node_if != 0) {
                uint32_t else_tok = lastToken(ag->tree, then_node_if) + 1;
                uint32_t err_tok = 0;
                if (else_tok + 1 < ag->tree->tokens.len
                    && ag->tree->tokens.tags[else_tok + 1] == TOKEN_PIPE) {
                    err_tok = else_tok + 2;
                }
                if (err_tok != 0) {
                    AstNodeTag else_tag = ag->tree->nodes.tags[else_node_if];
                    if ((else_tag == AST_NODE_SWITCH
                            || else_tag == AST_NODE_SWITCH_COMMA)
                        && ag->tree->tokens.tags[ag->tree->nodes
                                   .main_tokens[else_node_if]]
                            == TOKEN_KEYWORD_SWITCH) {
                        uint32_t sw_cond
                            = ag->tree->nodes.datas[else_node_if].lhs;
                        if (ag->tree->nodes.tags[sw_cond]
                                == AST_NODE_IDENTIFIER
                            && tokenIdentEql(ag->tree, err_tok,
                                ag->tree->nodes.main_tokens[sw_cond])) {
                            return switchExprErrUnion(
                                gz, scope, rlBr(rl), node, 1);
                        }
                    }
                }
            }
        }
        return ifExpr(gz, scope, rlBr(rl), node);
    }
    // for (AstGen.zig:1043-1060).
    case AST_NODE_FOR_SIMPLE:
    case AST_NODE_FOR:
        return forExpr(gz, scope, rlBr(rl), node, false);
    // Merge error sets (AstGen.zig:788-797).
    case AST_NODE_MERGE_ERROR_SETS: {
        uint32_t lhs = typeExpr(gz, scope, nd.lhs);
        uint32_t rhs = typeExpr(gz, scope, nd.rhs);
        return rvalue(gz, rl,
            addPlNodeBin(gz, ZIR_INST_MERGE_ERROR_SETS, node, lhs, rhs), node);
    }
    // Wrapping arithmetic (AstGen.zig:751-758).
    case AST_NODE_ADD_WRAP:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_ADDWRAP), node);
    case AST_NODE_SUB_WRAP:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_SUBWRAP), node);
    case AST_NODE_MUL_WRAP:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_MULWRAP), node);
    // Saturating arithmetic (AstGen.zig:752-761).
    case AST_NODE_ADD_SAT:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_ADD_SAT), node);
    case AST_NODE_SUB_SAT:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_SUB_SAT), node);
    case AST_NODE_MUL_SAT:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_MUL_SAT), node);
    case AST_NODE_SHL_SAT:
        return rvalue(
            gz, rl, simpleBinOp(gz, scope, node, ZIR_INST_SHL_SAT), node);
    // break (AstGen.zig:2150-2237).
    case AST_NODE_BREAK: {
        uint32_t opt_break_label = nd.lhs; // UINT32_MAX = none
        uint32_t opt_rhs = nd.rhs; // 0 = none

        // Walk scope chain to find target block (AstGen.zig:2157-2187).
        for (Scope* s = scope; s != NULL;) {
            if (s->tag == SCOPE_GEN_ZIR) {
                GenZir* block_gz = (GenZir*)s;
                uint32_t block_inst = UINT32_MAX;
                if (opt_break_label != UINT32_MAX) {
                    // Labeled break: check label on GenZir.
                    // Use direct source text comparison, not identAsString,
                    // to avoid adding label names to string_bytes
                    // (AstGen.zig:2176 uses tokenIdentEql).
                    if (block_gz->label_token != UINT32_MAX
                        && tokenIdentEql(ag->tree, opt_break_label,
                            block_gz->label_token)) {
                        block_inst = block_gz->label_block_inst;
                    }
                } else {
                    // Unlabeled break: check break_block.
                    if (block_gz->break_block != UINT32_MAX)
                        block_inst = block_gz->break_block;
                }
                if (block_inst != UINT32_MAX) {
                    // Found target (AstGen.zig:2188-2228).
                    ZirInstTag break_tag = block_gz->is_inline
                        ? ZIR_INST_BREAK_INLINE
                        : ZIR_INST_BREAK;
                    if (opt_rhs == 0) {
                        // Void break (AstGen.zig:2195-2206).
                        rvalue(gz, block_gz->break_result_info,
                            ZIR_REF_VOID_VALUE, node);
                        genDefers(gz, s, scope, DEFER_NORMAL_ONLY);
                        if (!block_gz->is_comptime) {
                            ZirInstData rdata;
                            rdata.un_node.operand
                                = block_inst + ZIR_REF_START_INDEX;
                            rdata.un_node.src_node
                                = (int32_t)node - (int32_t)gz->decl_node_index;
                            addInstruction(gz,
                                ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL,
                                rdata);
                        }
                        addBreak(gz, break_tag, block_inst, ZIR_REF_VOID_VALUE,
                            AST_NODE_OFFSET_NONE);
                    } else {
                        // Value break (AstGen.zig:2208-2228).
                        uint32_t operand = exprRl(
                            gz, scope, block_gz->break_result_info, opt_rhs);
                        genDefers(gz, s, scope, DEFER_NORMAL_ONLY);
                        if (!block_gz->is_comptime)
                            restoreErrRetIndex(gz, block_inst,
                                block_gz->break_result_info, opt_rhs, operand);
                        switch (block_gz->break_result_info.tag) {
                        case RL_PTR:
                        case RL_DISCARD:
                            addBreak(gz, break_tag, block_inst,
                                ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
                            break;
                        default:
                            addBreak(gz, break_tag, block_inst, operand,
                                (int32_t)opt_rhs
                                    - (int32_t)gz->decl_node_index);
                            break;
                        }
                    }
                    return ZIR_REF_UNREACHABLE_VALUE;
                }
                s = block_gz->parent;
            } else if (s->tag == SCOPE_LOCAL_VAL) {
                s = ((ScopeLocalVal*)s)->parent;
            } else if (s->tag == SCOPE_LOCAL_PTR) {
                s = ((ScopeLocalPtr*)s)->parent;
            } else if (s->tag == SCOPE_DEFER_NORMAL
                || s->tag == SCOPE_DEFER_ERROR) {
                s = ((ScopeDefer*)s)->parent;
            } else if (s->tag == SCOPE_LABEL) {
                s = ((ScopeLabel*)s)->parent;
            } else {
                break;
            }
        }
        SET_ERROR(ag);
        return ZIR_REF_UNREACHABLE_VALUE;
    }
    // continue (AstGen.zig:2246-2340).
    case AST_NODE_CONTINUE: {
        // Walk scope chain to find GenZir with continue_block.
        for (Scope* s = scope; s != NULL;) {
            if (s->tag == SCOPE_GEN_ZIR) {
                GenZir* gz2 = (GenZir*)s;
                if (gz2->continue_block != UINT32_MAX) {
                    genDefers(gz, s, scope, DEFER_NORMAL_ONLY);
                    ZirInstTag break_tag = gz2->is_inline
                        ? ZIR_INST_BREAK_INLINE
                        : ZIR_INST_BREAK;
                    if (break_tag == ZIR_INST_BREAK_INLINE) {
                        // AstGen.zig:2328-2330.
                        addUnNode(gz, ZIR_INST_CHECK_COMPTIME_CONTROL_FLOW,
                            gz2->continue_block + ZIR_REF_START_INDEX, node);
                    }
                    // Restore error return index (AstGen.zig:2333-2334).
                    if (!gz2->is_comptime) {
                        ZirInstData rdata;
                        rdata.un_node.operand
                            = gz2->continue_block + ZIR_REF_START_INDEX;
                        rdata.un_node.src_node
                            = (int32_t)node - (int32_t)gz->decl_node_index;
                        addInstruction(gz,
                            ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL,
                            rdata);
                    }
                    addBreak(gz, break_tag, gz2->continue_block,
                        ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
                    return ZIR_REF_UNREACHABLE_VALUE;
                }
                s = gz2->parent;
            } else if (s->tag == SCOPE_LOCAL_VAL) {
                s = ((ScopeLocalVal*)s)->parent;
            } else if (s->tag == SCOPE_LOCAL_PTR) {
                s = ((ScopeLocalPtr*)s)->parent;
            } else if (s->tag == SCOPE_DEFER_NORMAL
                || s->tag == SCOPE_DEFER_ERROR) {
                s = ((ScopeDefer*)s)->parent;
            } else if (s->tag == SCOPE_LABEL) {
                s = ((ScopeLabel*)s)->parent;
            } else {
                break;
            }
        }
        SET_ERROR(ag);
        return ZIR_REF_UNREACHABLE_VALUE;
    }
    // comptime (AstGen.zig:1104-1105).
    case AST_NODE_COMPTIME: {
        // comptimeExprAst / comptimeExpr2 (AstGen.zig:2104, 1982).
        uint32_t body_node = nd.lhs;

        // If already comptime, just pass through (AstGen.zig:1990-1992).
        if (gz->is_comptime)
            return exprRl(gz, scope, rl, body_node);

        // Create comptime block (AstGen.zig:2078-2098).
        uint32_t block_inst
            = makeBlockInst(ag, ZIR_INST_BLOCK_COMPTIME, gz, node);
        GenZir block_scope = makeSubBlock(gz, scope);
        block_scope.is_comptime = true;

        // Transform RL to type-only (AstGen.zig:2084-2090).
        // Runtime-to-comptime boundary: can't pass runtime pointers.
        ResultLoc ty_only_rl;
        uint32_t res_ty = rlResultType(gz, rl, node);
        if (res_ty != 0)
            ty_only_rl = (ResultLoc) { .tag = RL_COERCED_TY,
                .data = res_ty,
                .src_node = 0,
                .ctx = rl.ctx };
        else
            ty_only_rl = (ResultLoc) {
                .tag = RL_NONE, .data = 0, .src_node = 0, .ctx = rl.ctx
            };

        uint32_t result = exprRl(&block_scope, scope, ty_only_rl, body_node);
        addBreak(&block_scope, ZIR_INST_BREAK_INLINE, block_inst, result,
            AST_NODE_OFFSET_NONE);
        setBlockComptimeBody(
            ag, &block_scope, block_inst, COMPTIME_REASON_COMPTIME_KEYWORD);
        gzAppendInstruction(gz, block_inst);

        // Apply rvalue to handle RL_PTR etc (AstGen.zig:2098).
        return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
    }
    // switch (AstGen.zig:1072-1078).
    case AST_NODE_SWITCH:
    case AST_NODE_SWITCH_COMMA:
        return switchExpr(gz, scope, rlBr(rl), node);
    // while (AstGen.zig:1037-1042).
    case AST_NODE_WHILE_SIMPLE:
    case AST_NODE_WHILE_CONT:
    case AST_NODE_WHILE:
        return whileExpr(gz, scope, rlBr(rl), node, false);
    // error_value (AstGen.zig:1005).
    case AST_NODE_ERROR_VALUE: {
        uint32_t error_token = ag->tree->nodes.main_tokens[node] + 2;
        uint32_t str = identAsString(ag, error_token);
        return rvalue(gz, rl,
            addStrTok(gz, ZIR_INST_ERROR_VALUE, str, error_token), node);
    }
    // error_set_decl (AstGen.zig:5905-5955).
    case AST_NODE_ERROR_SET_DECL: {
        AstData esd = ag->tree->nodes.datas[node];
        uint32_t lbrace = esd.lhs;
        uint32_t rbrace = esd.rhs;
        // Reserve 1 extra word for ErrorSetDecl.fields_len.
        ensureExtraCapacity(ag, 1 + (rbrace - lbrace));
        uint32_t payload_index = ag->extra_len;
        ag->extra_len++; // placeholder for fields_len
        uint32_t fields_len = 0;
        for (uint32_t tok = lbrace + 1; tok < rbrace; tok++) {
            TokenizerTag ttag = ag->tree->tokens.tags[tok];
            if (ttag == TOKEN_DOC_COMMENT || ttag == TOKEN_COMMA)
                continue;
            if (ttag == TOKEN_IDENTIFIER) {
                uint32_t str_index = identAsString(ag, tok);
                ensureExtraCapacity(ag, 1);
                ag->extra[ag->extra_len++] = str_index;
                fields_len++;
            }
        }
        ag->extra[payload_index] = fields_len;
        return rvalue(gz, rl,
            addPlNodePayloadIndex(
                gz, ZIR_INST_ERROR_SET_DECL, node, payload_index),
            node);
    }
    // assign in expr context (AstGen.zig:1011-1014).
    case AST_NODE_ASSIGN:
        assignStmt(gz, scope, node);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    // Compound assignment operators (AstGen.zig:689-744).
    case AST_NODE_ASSIGN_ADD:
        assignOp(gz, scope, node, ZIR_INST_ADD);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_SUB:
        assignOp(gz, scope, node, ZIR_INST_SUB);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_MUL:
        assignOp(gz, scope, node, ZIR_INST_MUL);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_DIV:
        assignOp(gz, scope, node, ZIR_INST_DIV);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_MOD:
        assignOp(gz, scope, node, ZIR_INST_MOD_REM);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_BIT_AND:
        assignOp(gz, scope, node, ZIR_INST_BIT_AND);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_BIT_OR:
        assignOp(gz, scope, node, ZIR_INST_BIT_OR);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_BIT_XOR:
        assignOp(gz, scope, node, ZIR_INST_XOR);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_ADD_WRAP:
        assignOp(gz, scope, node, ZIR_INST_ADDWRAP);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_SUB_WRAP:
        assignOp(gz, scope, node, ZIR_INST_SUBWRAP);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_MUL_WRAP:
        assignOp(gz, scope, node, ZIR_INST_MULWRAP);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_ADD_SAT:
        assignOp(gz, scope, node, ZIR_INST_ADD_SAT);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_SUB_SAT:
        assignOp(gz, scope, node, ZIR_INST_SUB_SAT);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_MUL_SAT:
        assignOp(gz, scope, node, ZIR_INST_MUL_SAT);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    // Shift assignment operators (AstGen.zig:676-687).
    case AST_NODE_ASSIGN_SHL:
        assignShift(gz, scope, node, ZIR_INST_SHL);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_SHR:
        assignShift(gz, scope, node, ZIR_INST_SHR);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    case AST_NODE_ASSIGN_SHL_SAT:
        assignShiftSat(gz, scope, node);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    // assign_destructure (AstGen.zig:669-674).
    case AST_NODE_ASSIGN_DESTRUCTURE:
        assignDestructure(gz, scope, node);
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }
}

static uint32_t expr(GenZir* gz, Scope* scope, uint32_t node) {
    return exprRl(gz, scope, RL_NONE_VAL, node);
}

// --- blockExprExpr (AstGen.zig:2388-2536) ---
// Handles block expressions (labeled and unlabeled).
// Unlabeled blocks just execute statements and return void.
// Labeled blocks (blk: { ... break :blk val; }) need a block instruction.

static uint32_t blockExprExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract statements.
    uint32_t stmt_buf[2];
    const uint32_t* statements = NULL;
    uint32_t stmt_count = 0;

    switch (tag) {
    case AST_NODE_BLOCK_TWO:
    case AST_NODE_BLOCK_TWO_SEMICOLON: {
        uint32_t idx = 0;
        if (nd.lhs != 0)
            stmt_buf[idx++] = nd.lhs;
        if (nd.rhs != 0)
            stmt_buf[idx++] = nd.rhs;
        statements = stmt_buf;
        stmt_count = idx;
        break;
    }
    case AST_NODE_BLOCK:
    case AST_NODE_BLOCK_SEMICOLON: {
        uint32_t start = nd.lhs;
        uint32_t end = nd.rhs;
        statements = tree->extra_data.arr + start;
        stmt_count = end - start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Check if labeled (AstGen.zig:2397-2402).
    // A labeled block has: identifier colon before the lbrace.
    uint32_t lbrace = tree->nodes.main_tokens[node];
    bool is_labeled
        = (lbrace >= 2 && tree->tokens.tags[lbrace - 1] == TOKEN_COLON
            && tree->tokens.tags[lbrace - 2] == TOKEN_IDENTIFIER);

    if (!is_labeled) {
        if (!gz->is_comptime) {
            // Non-comptime unlabeled block (AstGen.zig:2404-2425).
            // Create block_inst FIRST, add to gz, then process body.
            uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK, gz, node);
            gzAppendInstruction(gz, block_inst);

            GenZir block_scope = makeSubBlock(gz, scope);
            blockExprStmts(
                &block_scope, &block_scope.base, statements, stmt_count);

            if (!endsWithNoReturn(&block_scope)) {
                // restore_err_ret_index on gz (AstGen.zig:2420).
                ZirInstData rdata;
                rdata.un_node.operand = block_inst + ZIR_REF_START_INDEX;
                rdata.un_node.src_node
                    = (int32_t)node - (int32_t)gz->decl_node_index;
                addInstruction(
                    gz, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);
                // break on block_scope (AstGen.zig:2422).
                addBreak(&block_scope, ZIR_INST_BREAK, block_inst,
                    ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
            }
            setBlockBody(ag, &block_scope, block_inst);
        } else {
            // Comptime unlabeled block: inline statements
            // (AstGen.zig:2426-2429).
            GenZir sub_gz = makeSubBlock(gz, scope);
            blockExprStmts(&sub_gz, &sub_gz.base, statements, stmt_count);
        }
        // AstGen.zig:2431
        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
    }

    // Labeled block (AstGen.zig:2466-2536).
    // Note: upstream blockExpr always passes force_comptime=false.
    uint32_t label_token = lbrace - 2;

    // Compute break result info (AstGen.zig:2484-2492).
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_ri = breakResultInfo(gz, rl, node, need_rl);
    bool need_result_rvalue = (break_ri.tag != rl.tag);

    // Reserve the block instruction (AstGen.zig:2500-2501).
    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK, gz, node);
    gzAppendInstruction(gz, block_inst);

    GenZir block_scope = makeSubBlock(gz, scope);
    // Set label on block_scope (AstGen.zig:2504-2508).
    block_scope.label_token = label_token;
    block_scope.label_block_inst = block_inst;
    block_scope.break_result_info = break_ri;

    // Process statements (AstGen.zig:2512).
    blockExprStmts(&block_scope, &block_scope.base, statements, stmt_count);

    if (!endsWithNoReturn(&block_scope)) {
        // Emit restore_err_ret_index (AstGen.zig:2515).
        ZirInstData rdata;
        rdata.un_node.operand = block_inst + ZIR_REF_START_INDEX;
        rdata.un_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        addInstruction(
            gz, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);
        // rvalue + break (AstGen.zig:2516-2518).
        uint32_t result = rvalue(
            gz, block_scope.break_result_info, ZIR_REF_VOID_VALUE, node);
        addBreak(&block_scope, ZIR_INST_BREAK, block_inst, result,
            AST_NODE_OFFSET_NONE);
    }

    setBlockBody(ag, &block_scope, block_inst);

    // AstGen.zig:2531-2534.
    if (need_result_rvalue)
        return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
    return block_inst + ZIR_REF_START_INDEX;
}

// --- arrayInitDotExpr (AstGen.zig:1576-1595) ---
// Handles anonymous array init: `.{a, b, c}`.
// Emits array_init_anon instruction with MultiOp payload.

static uint32_t arrayInitDotExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract elements.
    uint32_t elem_buf[2];
    const uint32_t* elements = NULL;
    uint32_t elem_count = 0;

    switch (tag) {
    case AST_NODE_ARRAY_INIT_DOT_TWO:
    case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA: {
        uint32_t idx = 0;
        if (nd.lhs != 0)
            elem_buf[idx++] = nd.lhs;
        if (nd.rhs != 0)
            elem_buf[idx++] = nd.rhs;
        elements = elem_buf;
        elem_count = idx;
        break;
    }
    case AST_NODE_ARRAY_INIT_DOT:
    case AST_NODE_ARRAY_INIT_DOT_COMMA: {
        uint32_t start = nd.lhs;
        uint32_t end = nd.rhs;
        elements = tree->extra_data.arr + start;
        elem_count = end - start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Dispatch based on RL (AstGen.zig:1515-1572).
    switch (rl.tag) {
    case RL_NONE: {
        // arrayInitExprAnon (AstGen.zig:1576-1595).
        ensureExtraCapacity(ag, 1 + elem_count);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = elem_count;
        uint32_t extra_start = ag->extra_len;
        ag->extra_len += elem_count;
        for (uint32_t i = 0; i < elem_count; i++) {
            uint32_t elem_ref = expr(gz, scope, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
        return addPlNodePayloadIndex(
            gz, ZIR_INST_ARRAY_INIT_ANON, node, payload_index);
    }
    case RL_TY:
    case RL_COERCED_TY: {
        // validate_array_init_result_ty + arrayInitExprTyped
        // (AstGen.zig:1534-1539).
        uint32_t result_ty = rl.data;
        // Emit ArrayInit { ty, init_count } payload for
        // validate_array_init_result_ty.
        ensureExtraCapacity(ag, 2);
        uint32_t val_payload = ag->extra_len;
        ag->extra[ag->extra_len++] = result_ty;
        ag->extra[ag->extra_len++] = elem_count;
        addPlNodePayloadIndex(
            gz, ZIR_INST_VALIDATE_ARRAY_INIT_RESULT_TY, node, val_payload);

        // arrayInitExprTyped (AstGen.zig:1598-1642) with elem_ty=none.
        uint32_t operands_len = elem_count + 1; // +1 for type
        ensureExtraCapacity(ag, 1 + operands_len);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = operands_len;
        ag->extra[ag->extra_len++] = result_ty;
        uint32_t extra_start = ag->extra_len;
        ag->extra_len += elem_count;
        for (uint32_t i = 0; i < elem_count; i++) {
            // array_init_elem_type uses bin data (AstGen.zig:1626-1632).
            uint32_t elem_ty
                = addBin(gz, ZIR_INST_ARRAY_INIT_ELEM_TYPE, result_ty, i);
            ResultLoc elem_rl
                = { .tag = RL_COERCED_TY, .data = elem_ty, .src_node = 0 };
            uint32_t elem_ref = exprRl(gz, scope, elem_rl, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
        return addPlNodePayloadIndex(
            gz, ZIR_INST_ARRAY_INIT, node, payload_index);
    }
    case RL_INFERRED_PTR: {
        // arrayInitExprAnon + rvalue (AstGen.zig:1545-1551).
        ensureExtraCapacity(ag, 1 + elem_count);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = elem_count;
        uint32_t extra_start = ag->extra_len;
        ag->extra_len += elem_count;
        for (uint32_t i = 0; i < elem_count; i++) {
            uint32_t elem_ref = expr(gz, scope, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
        uint32_t result = addPlNodePayloadIndex(
            gz, ZIR_INST_ARRAY_INIT_ANON, node, payload_index);
        return rvalue(gz, rl, result, node);
    }
    case RL_DISCARD: {
        // Evaluate and discard each element (AstGen.zig:1517-1522).
        for (uint32_t i = 0; i < elem_count; i++) {
            exprRl(gz, scope, RL_DISCARD_VAL, elements[i]);
        }
        return ZIR_REF_VOID_VALUE;
    }
    case RL_REF: {
        // arrayInitExprAnon + ref (AstGen.zig:1523-1526).
        ensureExtraCapacity(ag, 1 + elem_count);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = elem_count;
        uint32_t extra_start = ag->extra_len;
        ag->extra_len += elem_count;
        for (uint32_t i = 0; i < elem_count; i++) {
            uint32_t elem_ref = expr(gz, scope, elements[i]);
            ag->extra[extra_start + i] = elem_ref;
        }
        uint32_t result = addPlNodePayloadIndex(
            gz, ZIR_INST_ARRAY_INIT_ANON, node, payload_index);
        return rvalue(gz, rl, result, node);
    }
    case RL_REF_COERCED_TY: {
        // validate_array_init_ref_ty + arrayInitExprTyped
        // (AstGen.zig:1527-1532).
        uint32_t ptr_ty_inst = rl.data;
        ensureExtraCapacity(ag, 2);
        uint32_t val_payload = ag->extra_len;
        ag->extra[ag->extra_len++] = ptr_ty_inst;
        ag->extra[ag->extra_len++] = elem_count;
        uint32_t dest_arr_ty_inst = addPlNodePayloadIndex(
            gz, ZIR_INST_VALIDATE_ARRAY_INIT_REF_TY, node, val_payload);

        // arrayInitExprTyped with elem_ty=none, is_ref=true.
        uint32_t operands_len = elem_count + 1;
        ensureExtraCapacity(ag, 1 + operands_len);
        uint32_t ai_payload = ag->extra_len;
        ag->extra[ag->extra_len++] = operands_len;
        ag->extra[ag->extra_len++] = dest_arr_ty_inst;
        uint32_t extra_start2 = ag->extra_len;
        ag->extra_len += elem_count;
        for (uint32_t i = 0; i < elem_count; i++) {
            // array_init_elem_type uses bin data (AstGen.zig:1626-1632).
            uint32_t elem_ty = addBin(
                gz, ZIR_INST_ARRAY_INIT_ELEM_TYPE, dest_arr_ty_inst, i);
            ResultLoc elem_rl
                = { .tag = RL_COERCED_TY, .data = elem_ty, .src_node = 0 };
            uint32_t elem_ref = exprRl(gz, scope, elem_rl, elements[i]);
            ag->extra[extra_start2 + i] = elem_ref;
        }
        return addPlNodePayloadIndex(
            gz, ZIR_INST_ARRAY_INIT_REF, node, ai_payload);
    }
    case RL_PTR: {
        // arrayInitExprPtr (AstGen.zig:1541-1543, 1645-1672).
        uint32_t array_ptr_inst
            = addUnNode(gz, ZIR_INST_OPT_EU_BASE_PTR_INIT, rl.data, node);
        // Block payload: body_len = elem_count.
        ensureExtraCapacity(ag, 1 + elem_count);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = elem_count;
        uint32_t items_start = ag->extra_len;
        ag->extra_len += elem_count;

        for (uint32_t i = 0; i < elem_count; i++) {
            // array_init_elem_ptr: ElemPtrImm{ptr, index}.
            uint32_t elem_ptr_inst = addPlNodeBin(gz,
                ZIR_INST_ARRAY_INIT_ELEM_PTR, elements[i], array_ptr_inst, i);
            ag->extra[items_start + i]
                = elem_ptr_inst - ZIR_REF_START_INDEX; // .toIndex()
            // Evaluate element with ptr RL (AstGen.zig:1668).
            // Upstream creates fresh ResultInfo with default ctx (.none).
            ResultLoc ptr_rl = { .tag = RL_PTR,
                .data = elem_ptr_inst,
                .src_node = 0,
                .ctx = RI_CTX_NONE };
            exprRl(gz, scope, ptr_rl, elements[i]);
        }
        addPlNodePayloadIndex(
            gz, ZIR_INST_VALIDATE_PTR_ARRAY_INIT, node, payload_index);
        return ZIR_REF_VOID_VALUE;
    }
    case RL_DESTRUCTURE: {
        // Destructure directly into result pointers (AstGen.zig:1552-1569).
        if (elem_count != rl.components_len) {
            SET_ERROR(ag);
            return ZIR_REF_VOID_VALUE;
        }
        for (uint32_t i = 0; i < elem_count; i++) {
            const DestructureComponent* comp = &rl.components[i];
            ResultLoc elem_rl;
            switch (comp->tag) {
            case DC_TYPED_PTR:
                elem_rl = (ResultLoc) { .tag = RL_PTR,
                    .data = comp->inst,
                    .src_node = comp->src_node,
                    .ctx = RI_CTX_NONE };
                break;
            case DC_INFERRED_PTR:
                elem_rl = (ResultLoc) { .tag = RL_INFERRED_PTR,
                    .data = comp->inst,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                break;
            case DC_DISCARD:
                elem_rl = RL_DISCARD_VAL;
                break;
            }
            exprRl(gz, scope, elem_rl, elements[i]);
        }
        return ZIR_REF_VOID_VALUE;
    }
    }

    // Fallback: anon init + rvalue.
    ensureExtraCapacity(ag, 1 + elem_count);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = elem_count;
    uint32_t extra_start = ag->extra_len;
    ag->extra_len += elem_count;
    for (uint32_t i = 0; i < elem_count; i++) {
        uint32_t elem_ref = expr(gz, scope, elements[i]);
        ag->extra[extra_start + i] = elem_ref;
    }
    uint32_t result = addPlNodePayloadIndex(
        gz, ZIR_INST_ARRAY_INIT_ANON, node, payload_index);
    return rvalue(gz, rl, result, node);
}

// --- ifExpr (AstGen.zig:6300-6528) ---
// Handles if and if_simple expressions.
// Pattern: block_scope with condbr → then/else branches → setCondBrPayload.

static uint32_t ifExpr(GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_rl = breakResultInfo(gz, rl, node, need_rl);
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    uint32_t cond_node = nd.lhs;
    uint32_t then_node, else_node;

    if (tag == AST_NODE_IF_SIMPLE) {
        then_node = nd.rhs;
        else_node = 0;
    } else {
        // AST_NODE_IF: rhs is index into extra -> If{then_expr, else_expr}
        then_node = tree->extra_data.arr[nd.rhs];
        else_node = tree->extra_data.arr[nd.rhs + 1];
    }

    // Detect payload capture: if (cond) |x| (AstGen.zig Ast.fullIf).
    // payload_pipe = lastToken(cond_expr) + 2; if pipe -> payload_token + 1.
    uint32_t payload_token = 0; // 0 = no payload
    uint32_t last_cond_tok = lastToken(tree, cond_node);
    uint32_t pipe_tok = last_cond_tok + 2;
    if (pipe_tok < tree->tokens.len
        && tree->tokens.tags[pipe_tok] == TOKEN_PIPE) {
        payload_token = pipe_tok + 1; // identifier or * token
    }

    // Detect error token: then_expr else |e| (AstGen.zig Ast.fullIf).
    uint32_t error_token = 0;
    if (else_node != 0) {
        uint32_t else_tok = lastToken(tree, then_node) + 1; // "else" keyword
        if (else_tok + 1 < tree->tokens.len
            && tree->tokens.tags[else_tok + 1] == TOKEN_PIPE) {
            error_token = else_tok + 2;
        }
    }

    // Detect payload_is_ref: if payload_token is '*' (AstGen.zig:6330-6333).
    bool payload_is_ref = (payload_token != 0
        && tree->tokens.tags[payload_token] == TOKEN_ASTERISK);

    // Create block_scope (AstGen.zig:6326-6328).
    GenZir block_scope = makeSubBlock(gz, scope);

    // Emit DBG_STMT for condition (AstGen.zig:6335).
    // NOTE: upstream emits into parent_gz AFTER block_scope is created,
    // so the dbg_stmt ends up in block_scope's range (shared array).
    emitDbgNode(gz, cond_node);

    // Evaluate condition (AstGen.zig:6336-6363).
    uint32_t cond_inst; // the value (optional/err-union/bool)
    uint32_t bool_bit; // the boolean for condbr
    if (error_token != 0) {
        // Error union condition: if (err_union) |val| else |err|.
        // (AstGen.zig:6340-6347).
        ResultLoc cond_rl = payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;
        cond_rl.ctx = RI_CTX_ERROR_HANDLING_EXPR;
        cond_inst
            = exprRl(&block_scope, &block_scope.base, cond_rl, cond_node);
        ZirInstTag cond_tag
            = payload_is_ref ? ZIR_INST_IS_NON_ERR_PTR : ZIR_INST_IS_NON_ERR;
        bool_bit = addUnNode(&block_scope, cond_tag, cond_inst, cond_node);
    } else if (payload_token != 0) {
        // Optional condition: if (optional) |val| (AstGen.zig:6348-6355).
        ResultLoc cond_rl = payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;
        cond_inst
            = exprRl(&block_scope, &block_scope.base, cond_rl, cond_node);
        ZirInstTag cond_tag
            = payload_is_ref ? ZIR_INST_IS_NON_NULL_PTR : ZIR_INST_IS_NON_NULL;
        bool_bit = addUnNode(&block_scope, cond_tag, cond_inst, cond_node);
    } else {
        // Bool condition (AstGen.zig:6356-6362).
        ResultLoc coerced_bool_ri = {
            .tag = RL_COERCED_TY,
            .data = ZIR_REF_BOOL_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
        };
        cond_inst = exprRl(
            &block_scope, &block_scope.base, coerced_bool_ri, cond_node);
        bool_bit = cond_inst;
    }

    uint32_t condbr = addCondBr(&block_scope, ZIR_INST_CONDBR, node);
    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK, gz, node);
    setBlockBody(ag, &block_scope, block_inst);
    gzAppendInstruction(gz, block_inst);

    // Then branch (AstGen.zig:6372-6441).
    GenZir then_scope = makeSubBlock(gz, scope);
    Scope* then_sub_scope = &then_scope.base;
    ScopeLocalVal payload_val_scope;
    memset(&payload_val_scope, 0, sizeof(payload_val_scope));

    if (error_token != 0 && payload_token != 0) {
        // Error union with payload: unwrap payload (AstGen.zig:6379-6403).
        ZirInstTag unwrap_tag = payload_is_ref
            ? ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE_PTR
            : ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE;
        uint32_t payload_inst
            = addUnNode(&then_scope, unwrap_tag, cond_inst, then_node);
        uint32_t name_token = payload_token + (payload_is_ref ? 1u : 0u);
        if (tokenIsUnderscore(tree, name_token)) {
            // Discard (AstGen.zig:6389-6391).
            if (payload_is_ref) {
                SET_ERROR(ag);
                return ZIR_REF_VOID_VALUE;
            }
            // then_sub_scope stays as &then_scope.base
        } else {
            uint32_t ident_name = identAsString(ag, name_token);
            payload_val_scope = (ScopeLocalVal) {
                .base = { .tag = SCOPE_LOCAL_VAL },
                .parent = &then_scope.base,
                .gen_zir = &then_scope,
                .inst = payload_inst,
                .token_src = name_token,
                .name = ident_name,
            };
            addDbgVar(
                &then_scope, ZIR_INST_DBG_VAR_VAL, ident_name, payload_inst);
            then_sub_scope = &payload_val_scope.base;
        }
    } else if (error_token != 0) {
        // Error union without payload: ensure payload is void
        // (AstGen.zig:6404-6406).
        addUnNode(&then_scope, ZIR_INST_ENSURE_ERR_UNION_PAYLOAD_VOID,
            cond_inst, node);
    } else if (payload_token != 0) {
        // Optional with payload: unwrap optional (AstGen.zig:6408-6431).
        uint32_t ident_token = payload_token + (payload_is_ref ? 1u : 0u);
        if (tokenIsUnderscore(tree, ident_token)) {
            // Discard (AstGen.zig:6415-6417).
            if (payload_is_ref) {
                SET_ERROR(ag);
                return ZIR_REF_VOID_VALUE;
            }
            // then_sub_scope stays as &then_scope.base
        } else {
            ZirInstTag unwrap_tag = payload_is_ref
                ? ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE_PTR
                : ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE;
            uint32_t payload_inst
                = addUnNode(&then_scope, unwrap_tag, cond_inst, then_node);
            uint32_t ident_name = identAsString(ag, ident_token);
            payload_val_scope = (ScopeLocalVal) {
                .base = { .tag = SCOPE_LOCAL_VAL },
                .parent = &then_scope.base,
                .gen_zir = &then_scope,
                .inst = payload_inst,
                .token_src = ident_token,
                .name = ident_name,
            };
            addDbgVar(
                &then_scope, ZIR_INST_DBG_VAR_VAL, ident_name, payload_inst);
            then_sub_scope = &payload_val_scope.base;
        }
    }

    // Use fullBodyExpr for then body (AstGen.zig:6437).
    uint32_t then_result
        = fullBodyExpr(&then_scope, then_sub_scope, break_rl, then_node);
    if (!endsWithNoReturn(&then_scope)) {
        addBreak(&then_scope, ZIR_INST_BREAK, block_inst, then_result,
            (int32_t)then_node - (int32_t)gz->decl_node_index);
    }

    // Else branch (AstGen.zig:6443-6489).
    GenZir else_scope = makeSubBlock(gz, scope);

    // save_err_ret_index (AstGen.zig:6448-6449).
    bool do_err_trace = ag->fn_ret_ty != 0 && error_token != 0;
    if (do_err_trace && nodeMayAppendToErrorTrace(tree, cond_node))
        addSaveErrRetIndex(&else_scope, ZIR_REF_NONE);

    if (else_node != 0) {
        Scope* else_sub_scope = &else_scope.base;
        ScopeLocalVal error_val_scope;
        memset(&error_val_scope, 0, sizeof(error_val_scope));

        if (error_token != 0) {
            // Error capture: else |err| (AstGen.zig:6452-6475).
            ZirInstTag err_tag = payload_is_ref ? ZIR_INST_ERR_UNION_CODE_PTR
                                                : ZIR_INST_ERR_UNION_CODE;
            uint32_t err_inst
                = addUnNode(&else_scope, err_tag, cond_inst, cond_node);
            // identAsString must be called before the underscore check,
            // matching upstream order (AstGen.zig:6459-6462).
            uint32_t err_name = identAsString(ag, error_token);
            if (tokenIsUnderscore(tree, error_token)) {
                // Discard |_| (AstGen.zig:6461-6462).
                // else_sub_scope stays as &else_scope.base
            } else {
                error_val_scope = (ScopeLocalVal) {
                    .base = { .tag = SCOPE_LOCAL_VAL },
                    .parent = &else_scope.base,
                    .gen_zir = &else_scope,
                    .inst = err_inst,
                    .token_src = error_token,
                    .name = err_name,
                };
                addDbgVar(
                    &else_scope, ZIR_INST_DBG_VAR_VAL, err_name, err_inst);
                else_sub_scope = &error_val_scope.base;
            }
        }

        // Use fullBodyExpr for else body (AstGen.zig:6478).
        uint32_t else_result
            = fullBodyExpr(&else_scope, else_sub_scope, break_rl, else_node);
        if (!endsWithNoReturn(&else_scope)) {
            // Restore error return index (AstGen.zig:6480-6482).
            if (do_err_trace)
                restoreErrRetIndex(
                    &else_scope, block_inst, break_rl, else_node, else_result);
            addBreak(&else_scope, ZIR_INST_BREAK, block_inst, else_result,
                (int32_t)else_node - (int32_t)gz->decl_node_index);
        }
    } else {
        // No else branch (AstGen.zig:6486-6488).
        uint32_t else_result
            = rvalue(&else_scope, rl, ZIR_REF_VOID_VALUE, node);
        addBreak(&else_scope, ZIR_INST_BREAK, block_inst, else_result,
            AST_NODE_OFFSET_NONE);
    }

    // Wire up condbr (AstGen.zig:6491).
    setCondBrPayload(ag, condbr, bool_bit, &then_scope, &else_scope);

    // AstGen.zig:6493-6497.
    bool need_result_rvalue = (break_rl.tag != rl.tag);
    if (need_result_rvalue)
        return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
    return block_inst + ZIR_REF_START_INDEX;
}

// --- forExpr (AstGen.zig:6819-7125) ---
// Handles for_simple and for (multi-input).
// Supports both indexable and for_range inputs.

#define FOR_MAX_INPUTS 16

static uint32_t forExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, bool is_statement) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];
    AstNodeTag node_tag = tree->nodes.tags[node];

    // Detect inline keyword (AstGen.zig:6847).
    uint32_t main_token = tree->nodes.main_tokens[node];
    bool is_inline = (main_token > 0
        && tree->tokens.tags[main_token - 1] == TOKEN_KEYWORD_INLINE);

    // Compute label_token (AstGen.zig fullForComponents:2341-2348).
    uint32_t label_token = UINT32_MAX;
    {
        uint32_t tok_i = main_token;
        if (is_inline)
            tok_i = main_token - 1;
        if (tok_i >= 2 && tree->tokens.tags[tok_i - 2] == TOKEN_IDENTIFIER
            && tree->tokens.tags[tok_i - 1] == TOKEN_COLON)
            label_token = tok_i - 2;
    }

    // Compute break_rl from rl (AstGen.zig:6833-6845).
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_rl = breakResultInfo(gz, rl, node, need_rl);
    bool need_result_rvalue = (break_rl.tag != rl.tag);

    // Extract input nodes and body/else nodes.
    // FOR_SIMPLE: lhs = input node, rhs = body (Ast.zig:1960-1968).
    // FOR: lhs = extra_data index, rhs = packed AstFor (Ast.zig:1970-1981).
    uint32_t input_nodes[FOR_MAX_INPUTS];
    uint32_t num_inputs;
    uint32_t body_node;
    uint32_t else_node = 0;
    if (node_tag == AST_NODE_FOR_SIMPLE) {
        input_nodes[0] = nd.lhs;
        num_inputs = 1;
        body_node = nd.rhs;
    } else {
        uint32_t extra_idx = nd.lhs;
        AstFor for_data;
        memcpy(&for_data, &nd.rhs, sizeof(AstFor));
        num_inputs = for_data.inputs;
        if (num_inputs == 0 || num_inputs > FOR_MAX_INPUTS) {
            SET_ERROR(ag);
            return ZIR_REF_VOID_VALUE;
        }
        for (uint32_t i = 0; i < num_inputs; i++)
            input_nodes[i] = tree->extra_data.arr[extra_idx + i];
        body_node = tree->extra_data.arr[extra_idx + num_inputs];
        if (for_data.has_else)
            else_node = tree->extra_data.arr[extra_idx + num_inputs + 1];
    }

    // Per-input arrays (AstGen.zig:6858-6862).
    uint32_t indexables[FOR_MAX_INPUTS];
    uint32_t lens[FOR_MAX_INPUTS][2]; // [ref0, ref1] per input

    // Allocate index counter (AstGen.zig:6865-6874).
    ZirInstTag alloc_tag
        = is_inline ? ZIR_INST_ALLOC_COMPTIME_MUT : ZIR_INST_ALLOC;
    uint32_t index_ptr = addUnNode(gz, alloc_tag, ZIR_REF_USIZE_TYPE, node);
    addPlNodeBin(gz, ZIR_INST_STORE_NODE, node, index_ptr, ZIR_REF_ZERO_USIZE);

    // Compute payload_token (AstGen.zig fullForComponents:2349-2350).
    // payload_token = lastToken(inputs[last]) + 3 + has_comma
    uint32_t last_cond_tok = lastToken(tree, input_nodes[num_inputs - 1]);
    bool has_comma = (last_cond_tok + 1 < tree->tokens.len
        && tree->tokens.tags[last_cond_tok + 1] == TOKEN_COMMA);
    uint32_t payload_token = last_cond_tok + 3 + (has_comma ? 1 : 0);

    bool any_len_checks = false;

    // Process each input (AstGen.zig:6878-6925).
    uint32_t capture_token = payload_token;
    for (uint32_t i = 0; i < num_inputs; i++) {
        uint32_t input = input_nodes[i];
        // Advance capture_token past this capture's ident (+comma).
        bool capture_is_ref
            = (tree->tokens.tags[capture_token] == TOKEN_ASTERISK);
        uint32_t ident_tok = capture_token + (capture_is_ref ? 1u : 0u);
        bool is_discard = tokenIsUnderscore(tree, ident_tok);
        capture_token = ident_tok + 2; // skip ident + comma/pipe

        // Diagnostic: pointer modifier invalid on discard
        // (AstGen.zig:6885-6887).
        if (is_discard && capture_is_ref) {
            SET_ERROR(ag);
            return ZIR_REF_VOID_VALUE;
        }

        emitDbgNode(gz, input);

        if (tree->nodes.tags[input] == AST_NODE_FOR_RANGE) {
            // Diagnostic: cannot capture reference to range
            // (AstGen.zig:6893-6895).
            if (capture_is_ref) {
                SET_ERROR(ag);
                return ZIR_REF_VOID_VALUE;
            }

            // Range input (AstGen.zig:6896-6916).
            AstData range_nd = tree->nodes.datas[input];
            uint32_t start_node = range_nd.lhs;
            uint32_t end_node = range_nd.rhs;

            // AstGen.zig:6897-6902: expr with .rl = .{ .ty = .usize_type }
            ResultLoc usize_rl = {
                .tag = RL_TY,
                .data = ZIR_REF_USIZE_TYPE,
                .src_node = 0,
                .ctx = RI_CTX_NONE,
            };
            uint32_t start_val = exprRl(gz, scope, usize_rl, start_node);

            uint32_t end_val = ZIR_REF_NONE;
            if (end_node != 0) {
                end_val = exprRl(gz, scope, usize_rl, end_node);
            }

            // Diagnostic: discard of unbounded counter
            // (AstGen.zig:6904-6906).
            if (end_val == ZIR_REF_NONE && is_discard) {
                SET_ERROR(ag);
            }

            if (end_val == ZIR_REF_NONE) {
                lens[i][0] = ZIR_REF_NONE;
                lens[i][1] = ZIR_REF_NONE;
            } else {
                any_len_checks = true;
                lens[i][0] = start_val;
                lens[i][1] = end_val;
            }

            // Check if start is trivially zero.
            bool start_is_zero = false;
            if (tree->nodes.tags[start_node] == AST_NODE_NUMBER_LITERAL) {
                uint32_t tok = tree->nodes.main_tokens[start_node];
                uint32_t ts = tree->tokens.starts[tok];
                if (tree->source[ts] == '0'
                    && (ts + 1 >= tree->source_len
                        || tree->source[ts + 1] < '0'
                        || tree->source[ts + 1] > '9'))
                    start_is_zero = true;
            }
            indexables[i] = start_is_zero ? ZIR_REF_NONE : start_val;
        } else {
            // Regular indexable (AstGen.zig:6918-6923).
            uint32_t indexable = expr(gz, scope, input);
            any_len_checks = true;
            indexables[i] = indexable;
            lens[i][0] = indexable;
            lens[i][1] = ZIR_REF_NONE;
        }
    }

    // Error if no length checks exist (AstGen.zig:6927-6929).
    if (!any_len_checks) {
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Emit for_len as MultiOp (AstGen.zig:6933-6942).
    uint32_t len;
    {
        uint32_t operands_len = num_inputs * 2;
        ensureExtraCapacity(ag, 1 + operands_len);
        uint32_t payload_index = ag->extra_len;
        ag->extra[ag->extra_len++] = operands_len;
        for (uint32_t i = 0; i < num_inputs; i++) {
            ag->extra[ag->extra_len++] = lens[i][0];
            ag->extra[ag->extra_len++] = lens[i][1];
        }
        ZirInstData data;
        data.pl_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        data.pl_node.payload_index = payload_index;
        len = addInstruction(gz, ZIR_INST_FOR_LEN, data);
    }

    // Create loop (AstGen.zig:6944-6946).
    ZirInstTag loop_tag = is_inline ? ZIR_INST_BLOCK_INLINE : ZIR_INST_LOOP;
    uint32_t loop_inst = makeBlockInst(ag, loop_tag, gz, node);
    // Issue 3: append loop_inst to parent_gz immediately (AstGen.zig:6946).
    gzAppendInstruction(gz, loop_inst);

    GenZir loop_scope = makeSubBlock(gz, scope);
    loop_scope.is_inline = is_inline;
    // Issue 1: set break_result_info (AstGen.zig:6950).
    loop_scope.break_result_info = break_rl;

    // Load index (AstGen.zig:6955-6956).
    // We need to finish loop_scope later once we have the deferred refs from
    // then_scope. However, the load must be removed from instructions in the
    // meantime or it appears to be part of parent_gz.
    uint32_t index = addUnNode(&loop_scope, ZIR_INST_LOAD, index_ptr, node);
    ag->scratch_inst_len--; // pop from loop_scope (AstGen.zig:6956)

    // Condition: added to cond_scope (AstGen.zig:6958-6962).
    GenZir cond_scope = makeSubBlock(gz, &loop_scope.base);
    uint32_t cond
        = addPlNodeBin(&cond_scope, ZIR_INST_CMP_LT, node, index, len);

    // Create condbr + block (AstGen.zig:6967-6974).
    ZirInstTag condbr_tag
        = is_inline ? ZIR_INST_CONDBR_INLINE : ZIR_INST_CONDBR;
    uint32_t condbr = addCondBr(&cond_scope, condbr_tag, node);
    ZirInstTag block_tag = is_inline ? ZIR_INST_BLOCK_INLINE : ZIR_INST_BLOCK;
    uint32_t cond_block = makeBlockInst(ag, block_tag, &loop_scope, node);
    setBlockBody(ag, &cond_scope, cond_block);

    loop_scope.break_block = loop_inst;
    loop_scope.continue_block = cond_block; // AstGen.zig:6974
    // Issue 4: set label on loop_scope (AstGen.zig:6975-6980).
    if (label_token != UINT32_MAX) {
        loop_scope.label_token = label_token;
        loop_scope.label_block_inst = loop_inst;
    }

    // Then branch: loop body (AstGen.zig:6982-7065).
    GenZir then_scope = makeSubBlock(gz, &cond_scope.base);

    // Set up capture scopes for all inputs (AstGen.zig:6986-7045).
    ScopeLocalVal capture_scopes[FOR_MAX_INPUTS];
    Scope* body_scope_parent = &then_scope.base;
    {
        capture_token = payload_token;
        for (uint32_t i = 0; i < num_inputs; i++) {
            uint32_t input = input_nodes[i];
            bool capture_is_ref
                = (tree->tokens.tags[capture_token] == TOKEN_ASTERISK);
            uint32_t ident_tok = capture_token + (capture_is_ref ? 1u : 0u);
            capture_token = ident_tok + 2;

            // Check if discard (AstGen.zig:6999).
            bool is_discard = tokenIsUnderscore(tree, ident_tok);
            if (is_discard)
                continue;

            // Compute capture inst (AstGen.zig:7004-7028).
            uint32_t capture_inst;
            bool is_counter = (tree->nodes.tags[input] == AST_NODE_FOR_RANGE);

            if (indexables[i] == ZIR_REF_NONE) {
                // Start=0 counter: use index directly.
                capture_inst = index;
            } else if (is_counter) {
                // Counter with nonzero start: add.
                capture_inst = addPlNodeBin(
                    &then_scope, ZIR_INST_ADD, input, indexables[i], index);
            } else if (capture_is_ref) {
                // Indexable by ref: elem_ptr.
                capture_inst = addPlNodeBin(&then_scope, ZIR_INST_ELEM_PTR,
                    input, indexables[i], index);
            } else {
                // Indexable by val: elem_val.
                capture_inst = addPlNodeBin(&then_scope, ZIR_INST_ELEM_VAL,
                    input, indexables[i], index);
            }

            uint32_t name_str = identAsString(ag, ident_tok);
            capture_scopes[i] = (ScopeLocalVal) {
                .base = { .tag = SCOPE_LOCAL_VAL },
                .parent = body_scope_parent,
                .gen_zir = &then_scope,
                .inst = capture_inst,
                .token_src = ident_tok,
                .name = name_str,
            };
            // AstGen.zig:7040.
            addDbgVar(
                &then_scope, ZIR_INST_DBG_VAR_VAL, name_str, capture_inst);
            body_scope_parent = &capture_scopes[i].base;
        }
    }

    // Execute body (AstGen.zig:7047-7048).
    uint32_t then_result
        = fullBodyExpr(&then_scope, body_scope_parent, RL_NONE_VAL, body_node);
    addEnsureResult(&then_scope, then_result, body_node);

    // dbg_stmt + dbg_empty_stmt (AstGen.zig:7052-7061).
    advanceSourceCursor(ag, tree->tokens.starts[lastToken(tree, body_node)]);
    emitDbgStmt(gz, ag->source_line - gz->decl_line, ag->source_column);
    {
        ZirInstData ext_data;
        ext_data.extended.opcode = (uint16_t)ZIR_EXT_DBG_EMPTY_STMT;
        ext_data.extended.small = 0;
        ext_data.extended.operand = 0;
        addInstruction(gz, ZIR_INST_EXTENDED, ext_data);
    }

    ZirInstTag break_tag = is_inline ? ZIR_INST_BREAK_INLINE : ZIR_INST_BREAK;
    addBreak(&then_scope, break_tag, cond_block, ZIR_REF_VOID_VALUE,
        AST_NODE_OFFSET_NONE);

    // Else branch (AstGen.zig:7066-7091).
    GenZir else_scope = makeSubBlock(gz, &cond_scope.base);

    if (else_node != 0) {
        // Issue 2: evaluate else expression (AstGen.zig:7069-7081).
        // Remove continue/break blocks so that control flow applies
        // to outer loops (AstGen.zig:7073-7074).
        loop_scope.continue_block = UINT32_MAX;
        loop_scope.break_block = UINT32_MAX;
        uint32_t else_result = fullBodyExpr(&else_scope, &else_scope.base,
            loop_scope.break_result_info, else_node);
        if (is_statement) {
            addEnsureResult(&else_scope, else_result, else_node);
        }
        if (!endsWithNoReturn(&else_scope)) {
            addBreak(&else_scope, break_tag, loop_inst, else_result,
                (int32_t)else_node - (int32_t)gz->decl_node_index);
        }
    } else {
        // No else: break with void (AstGen.zig:7082-7085).
        uint32_t void_result
            = rvalue(&else_scope, rl, ZIR_REF_VOID_VALUE, node);
        addBreak(&else_scope, break_tag, loop_inst, void_result,
            AST_NODE_OFFSET_NONE);
    }

    // Issue 4: check unused label (AstGen.zig:7087-7091).
    if (label_token != UINT32_MAX) {
        // Note: upstream checks loop_scope.label.used; we don't track usage
        // yet, so skip the "unused for loop label" error for now.
    }

    setCondBrPayload(ag, condbr, cond, &then_scope, &else_scope);

    // then_scope and else_scope unstacked now. Resurrect loop_scope to
    // finally finish it (AstGen.zig:7095-7113).
    {
        // Reset loop_scope instructions and re-add index + cond_block.
        loop_scope.instructions_top = ag->scratch_inst_len;
        gzAppendInstruction(&loop_scope, index - ZIR_REF_START_INDEX);
        gzAppendInstruction(&loop_scope, cond_block);

        // Increment the index variable (AstGen.zig:7100-7108).
        uint32_t index_plus_one = addPlNodeBin(
            &loop_scope, ZIR_INST_ADD_UNSAFE, node, index, ZIR_REF_ONE_USIZE);
        addPlNodeBin(
            &loop_scope, ZIR_INST_STORE_NODE, node, index_ptr, index_plus_one);

        // Repeat (AstGen.zig:7110-7111).
        ZirInstTag repeat_tag
            = is_inline ? ZIR_INST_REPEAT_INLINE : ZIR_INST_REPEAT;
        ZirInstData repeat_data;
        memset(&repeat_data, 0, sizeof(repeat_data));
        repeat_data.node = (int32_t)node - (int32_t)loop_scope.decl_node_index;
        addInstruction(&loop_scope, repeat_tag, repeat_data);

        setBlockBody(ag, &loop_scope, loop_inst);
    }

    // Issue 1: apply rvalue if needed (AstGen.zig:7116-7119).
    uint32_t result;
    if (need_result_rvalue)
        result = rvalue(gz, rl, loop_inst + ZIR_REF_START_INDEX, node);
    else
        result = loop_inst + ZIR_REF_START_INDEX;

    // Emit ensure_result_used when used as statement (AstGen.zig:7121-7123).
    if (is_statement) {
        addUnNode(gz, ZIR_INST_ENSURE_RESULT_USED, result, node);
    }

    return result;
}

// --- orelseCatchExpr (AstGen.zig:6031-6142) ---
// Handles `lhs orelse rhs` and `lhs catch rhs`.

static uint32_t orelseCatchExpr(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, ZirInstTag cond_op, ZirInstTag unwrap_op,
    ZirInstTag unwrap_code_op, uint32_t payload_token) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];

    bool do_err_trace = ag->fn_ret_ty != 0
        && (cond_op == ZIR_INST_IS_NON_ERR
            || cond_op == ZIR_INST_IS_NON_ERR_PTR);

    // breakResultInfo (AstGen.zig:6046-6058).
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_rl = breakResultInfo(gz, rl, node, need_rl);
    bool need_result_rvalue = (break_rl.tag != rl.tag);

    // Create block_scope (AstGen.zig:6062-6063).
    GenZir block_scope = makeSubBlock(gz, scope);

    // Evaluate operand in block_scope (AstGen.zig:6066-6074).
    ResultLoc operand_rl;
    if (RL_IS_REF(break_rl)) {
        operand_rl = RL_REF_VAL;
    } else {
        operand_rl = RL_NONE_VAL;
    }
    if (do_err_trace) {
        operand_rl.ctx = RI_CTX_ERROR_HANDLING_EXPR;
    }
    uint32_t operand
        = exprRl(&block_scope, &block_scope.base, operand_rl, nd.lhs);

    // Check condition in block_scope (AstGen.zig:6075).
    uint32_t condition = addUnNode(&block_scope, cond_op, operand, node);

    // condbr in block_scope (AstGen.zig:6076).
    uint32_t condbr = addCondBr(&block_scope, ZIR_INST_CONDBR, node);

    // Create block in parent gz (AstGen.zig:6078-6081).
    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK, gz, node);
    setBlockBody(ag, &block_scope, block_inst);
    // block_scope unstacked now.
    gzAppendInstruction(gz, block_inst);

    // Then branch: unwrap payload (AstGen.zig:6083-6092).
    GenZir then_scope = makeSubBlock(&block_scope, scope);
    uint32_t unwrapped = addUnNode(&then_scope, unwrap_op, operand, node);
    // Apply rvalue coercion unless rl is ref/ref_coerced_ty
    // (AstGen.zig:6088-6091).
    uint32_t then_result = (rl.tag == RL_REF || rl.tag == RL_REF_COERCED_TY)
        ? unwrapped
        : rvalue(&then_scope, break_rl, unwrapped, node);
    addBreak(&then_scope, ZIR_INST_BREAK, block_inst, then_result,
        (int32_t)node - (int32_t)gz->decl_node_index);

    // Else branch: evaluate RHS (AstGen.zig:6094-6131).
    GenZir else_scope = makeSubBlock(&block_scope, scope);

    // save_err_ret_index (AstGen.zig:6099-6100).
    if (do_err_trace && nodeMayAppendToErrorTrace(tree, nd.lhs))
        addSaveErrRetIndex(&else_scope, ZIR_REF_NONE);

    // Error capture scope (AstGen.zig:6102-6123).
    ScopeLocalVal err_val_scope;
    memset(&err_val_scope, 0, sizeof(err_val_scope));
    Scope* else_sub_scope = &else_scope.base;
    if (payload_token != UINT32_MAX) {
        if (tokenIsUnderscore(tree, payload_token)) {
            // Discard |_| — else_sub_scope stays as &else_scope.base.
        } else {
            uint32_t err_name = identAsString(ag, payload_token);
            uint32_t err_inst
                = addUnNode(&else_scope, unwrap_code_op, operand, node);
            err_val_scope = (ScopeLocalVal) {
                .base = { .tag = SCOPE_LOCAL_VAL },
                .parent = &else_scope.base,
                .gen_zir = &else_scope,
                .inst = err_inst,
                .token_src = payload_token,
                .name = err_name,
            };
            else_sub_scope = &err_val_scope.base;
        }
    }

    // Use fullBodyExpr (not expr) to inline unlabeled blocks
    // (AstGen.zig:6125).
    uint32_t else_result
        = fullBodyExpr(&else_scope, else_sub_scope, break_rl, nd.rhs);
    if (!endsWithNoReturn(&else_scope)) {
        // restoreErrRetIndex (AstGen.zig:6128-6129).
        if (do_err_trace)
            restoreErrRetIndex(
                &else_scope, block_inst, break_rl, nd.rhs, else_result);
        addBreak(&else_scope, ZIR_INST_BREAK, block_inst, else_result,
            (int32_t)nd.rhs - (int32_t)gz->decl_node_index);
    }

    setCondBrPayload(ag, condbr, condition, &then_scope, &else_scope);

    // AstGen.zig:6137-6141.
    if (need_result_rvalue)
        return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
    return block_inst + ZIR_REF_START_INDEX;
}

// --- whileExpr (AstGen.zig:6529-6817) ---
// Handles while_simple, while_cont, while.
// Structure: loop { cond_block { cond, condbr }, repeat }
// condbr → then { [payload], continue_block { [cont_expr], body,
//                                             break continue }, break cond }
//        → else { [err_capture], else_body / break loop }

static uint32_t whileExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, bool is_statement) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag node_tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Compute break_rl from rl (AstGen.zig:6540-6548).
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_rl = breakResultInfo(gz, rl, node, need_rl);
    bool need_result_rvalue = (break_rl.tag != rl.tag);

    // Detect inline keyword (AstGen.zig:6558).
    uint32_t main_token = tree->nodes.main_tokens[node];
    bool is_inline = (main_token > 0
        && tree->tokens.tags[main_token - 1] == TOKEN_KEYWORD_INLINE);

    // Compute label_token (AstGen.zig fullWhileComponents:2310-2317).
    uint32_t label_token = UINT32_MAX;
    {
        uint32_t tok_i = main_token;
        if (is_inline)
            tok_i = main_token - 1;
        if (tok_i >= 2 && tree->tokens.tags[tok_i - 2] == TOKEN_IDENTIFIER
            && tree->tokens.tags[tok_i - 1] == TOKEN_COLON)
            label_token = tok_i - 2;
    }

    // Extract AST nodes depending on node type (Ast.zig:1925-1958).
    uint32_t cond_node = nd.lhs;
    uint32_t body_node;
    uint32_t else_node = 0;
    uint32_t cont_expr = 0; // 0 = none
    if (node_tag == AST_NODE_WHILE_SIMPLE) {
        body_node = nd.rhs;
    } else if (node_tag == AST_NODE_WHILE_CONT) {
        // WhileCont[rhs]: { cont_expr, then_expr }
        cont_expr = tree->extra_data.arr[nd.rhs];
        body_node = tree->extra_data.arr[nd.rhs + 1];
    } else {
        // AST_NODE_WHILE: While[rhs]: { cont_expr, then_expr, else_expr }
        // cont_expr is stored via OPT(): UINT32_MAX means none.
        uint32_t raw_cont = tree->extra_data.arr[nd.rhs];
        cont_expr = (raw_cont == UINT32_MAX) ? 0 : raw_cont;
        body_node = tree->extra_data.arr[nd.rhs + 1];
        else_node = tree->extra_data.arr[nd.rhs + 2];
    }

    // Detect payload capture (Ast.zig fullWhileComponents:2318-2321).
    uint32_t payload_token = 0;
    {
        uint32_t last_cond_tok = lastToken(tree, cond_node);
        if (last_cond_tok + 2 < tree->tokens.len
            && tree->tokens.tags[last_cond_tok + 2] == TOKEN_PIPE) {
            payload_token = last_cond_tok + 3;
        }
    }

    // Detect error token (Ast.zig fullWhileComponents:2322-2329).
    uint32_t error_token = 0;
    if (else_node != 0) {
        uint32_t else_tok = lastToken(tree, body_node) + 1;
        if (else_tok + 1 < tree->tokens.len
            && tree->tokens.tags[else_tok + 1] == TOKEN_PIPE) {
            error_token = else_tok + 2;
        }
    }

    // Detect payload_is_ref (AstGen.zig:6574-6577).
    bool payload_is_ref = (payload_token != 0
        && tree->tokens.tags[payload_token] == TOKEN_ASTERISK);

    // Create loop instruction (AstGen.zig:6562-6564).
    ZirInstTag loop_tag = is_inline ? ZIR_INST_BLOCK_INLINE : ZIR_INST_LOOP;
    uint32_t loop_inst = makeBlockInst(ag, loop_tag, gz, node);
    gzAppendInstruction(gz, loop_inst);

    GenZir loop_scope = makeSubBlock(gz, scope);
    loop_scope.is_inline = is_inline;
    loop_scope.break_result_info = break_rl;

    // Evaluate condition in cond_scope (AstGen.zig:6571-6607).
    GenZir cond_scope = makeSubBlock(gz, &loop_scope.base);

    // Emit debug node for the condition expression (AstGen.zig:6579).
    emitDbgNode(gz, cond_node);

    uint32_t cond_inst; // the value (optional/err-union/bool)
    uint32_t bool_bit; // the boolean for condbr
    if (error_token != 0) {
        // Error union condition (AstGen.zig:6584-6591).
        ResultLoc cond_rl = payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;
        cond_inst
            = fullBodyExpr(&cond_scope, &cond_scope.base, cond_rl, cond_node);
        ZirInstTag cond_tag
            = payload_is_ref ? ZIR_INST_IS_NON_ERR_PTR : ZIR_INST_IS_NON_ERR;
        bool_bit = addUnNode(&cond_scope, cond_tag, cond_inst, cond_node);
    } else if (payload_token != 0) {
        // Optional condition (AstGen.zig:6592-6599).
        ResultLoc cond_rl = payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;
        cond_inst
            = fullBodyExpr(&cond_scope, &cond_scope.base, cond_rl, cond_node);
        ZirInstTag cond_tag
            = payload_is_ref ? ZIR_INST_IS_NON_NULL_PTR : ZIR_INST_IS_NON_NULL;
        bool_bit = addUnNode(&cond_scope, cond_tag, cond_inst, cond_node);
    } else {
        // Bool condition (AstGen.zig:6600-6606).
        ResultLoc coerced_bool_ri = {
            .tag = RL_COERCED_TY,
            .data = ZIR_REF_BOOL_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
        };
        cond_inst = fullBodyExpr(
            &cond_scope, &cond_scope.base, coerced_bool_ri, cond_node);
        bool_bit = cond_inst;
    }

    // Create condbr + cond_block (AstGen.zig:6609-6615).
    ZirInstTag condbr_tag
        = is_inline ? ZIR_INST_CONDBR_INLINE : ZIR_INST_CONDBR;
    uint32_t condbr = addCondBr(&cond_scope, condbr_tag, node);
    ZirInstTag block_tag = is_inline ? ZIR_INST_BLOCK_INLINE : ZIR_INST_BLOCK;
    uint32_t cond_block = makeBlockInst(ag, block_tag, &loop_scope, node);
    setBlockBody(ag, &cond_scope, cond_block); // unstacks cond_scope
    gzAppendInstruction(&loop_scope, cond_block);

    // Payload handling (AstGen.zig:6623-6690).
    // Create payload instructions in the global inst array but don't add to
    // any scope's scratch area yet. then_scope and continue_scope are created
    // after loop_scope is finalized (to avoid scratch array overlap).
    uint32_t dbg_var_name = 0;
    uint32_t dbg_var_inst = 0;
    uint32_t opt_payload_raw_inst = UINT32_MAX; // raw inst index, not ref
    uint32_t payload_ref = 0;
    uint32_t payload_ident_token = 0;
    uint32_t payload_ident_name = 0;
    bool payload_has_scope = false; // true if we need a ScopeLocalVal

    if (error_token != 0 && payload_token != 0) {
        // Error union with payload: makeUnNode (AstGen.zig:6628-6655).
        ZirInstTag unwrap_tag = payload_is_ref
            ? ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE_PTR
            : ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE;
        ensureInstCapacity(ag, 1);
        uint32_t raw_idx = ag->inst_len;
        ag->inst_tags[raw_idx] = unwrap_tag;
        ZirInstData d;
        d.un_node.src_node = (int32_t)cond_node - (int32_t)gz->decl_node_index;
        d.un_node.operand = cond_inst;
        ag->inst_datas[raw_idx] = d;
        ag->inst_len++;
        payload_ref = raw_idx + ZIR_REF_START_INDEX;
        opt_payload_raw_inst = raw_idx;
        payload_ident_token = payload_token + (payload_is_ref ? 1u : 0u);
        if (tokenIsUnderscore(tree, payload_ident_token)) {
            if (payload_is_ref) {
                SET_ERROR(ag);
                return ZIR_REF_VOID_VALUE;
            }
        } else {
            payload_ident_name = identAsString(ag, payload_ident_token);
            payload_has_scope = true;
        }
    } else if (error_token != 0) {
        // Error union without payload (AstGen.zig:6656-6658).
        ensureInstCapacity(ag, 1);
        uint32_t raw_idx = ag->inst_len;
        ag->inst_tags[raw_idx] = ZIR_INST_ENSURE_ERR_UNION_PAYLOAD_VOID;
        ZirInstData d;
        d.un_node.src_node = (int32_t)node - (int32_t)gz->decl_node_index;
        d.un_node.operand = cond_inst;
        ag->inst_datas[raw_idx] = d;
        ag->inst_len++;
        opt_payload_raw_inst = raw_idx;
    } else if (payload_token != 0) {
        // Optional with payload: makeUnNode (AstGen.zig:6660-6686).
        ZirInstTag unwrap_tag = payload_is_ref
            ? ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE_PTR
            : ZIR_INST_OPTIONAL_PAYLOAD_UNSAFE;
        ensureInstCapacity(ag, 1);
        uint32_t raw_idx = ag->inst_len;
        ag->inst_tags[raw_idx] = unwrap_tag;
        ZirInstData d;
        d.un_node.src_node = (int32_t)cond_node - (int32_t)gz->decl_node_index;
        d.un_node.operand = cond_inst;
        ag->inst_datas[raw_idx] = d;
        ag->inst_len++;
        payload_ref = raw_idx + ZIR_REF_START_INDEX;
        opt_payload_raw_inst = raw_idx;
        payload_ident_token = payload_token + (payload_is_ref ? 1u : 0u);
        if (tokenIsUnderscore(tree, payload_ident_token)) {
            if (payload_is_ref) {
                SET_ERROR(ag);
                return ZIR_REF_VOID_VALUE;
            }
        } else {
            payload_ident_name = identAsString(ag, payload_ident_token);
            payload_has_scope = true;
        }
    }

    // Create continue_block (AstGen.zig:6695).
    // makeBlockInst doesn't add to scratch.
    uint32_t continue_block_inst = makeBlockInst(ag, block_tag, gz, node);

    // Add repeat to loop_scope (AstGen.zig:6697-6698).
    {
        ZirInstTag repeat_tag
            = is_inline ? ZIR_INST_REPEAT_INLINE : ZIR_INST_REPEAT;
        ZirInstData repeat_data;
        memset(&repeat_data, 0, sizeof(repeat_data));
        repeat_data.node = (int32_t)node - (int32_t)loop_scope.decl_node_index;
        addInstruction(&loop_scope, repeat_tag, repeat_data);
    }

    // Set loop body and configure break/continue (AstGen.zig:6700-6708).
    setBlockBody(ag, &loop_scope, loop_inst); // unstacks loop_scope
    loop_scope.break_block = loop_inst;
    loop_scope.continue_block = continue_block_inst;
    if (label_token != UINT32_MAX) {
        loop_scope.label_token = label_token;
        loop_scope.label_block_inst = loop_inst;
    }

    // Now create then_scope (AstGen.zig:6617-6621, 6711).
    // loop_scope is unstacked, scratch is clean.
    GenZir then_scope = makeSubBlock(gz, &cond_scope.base);
    Scope* then_sub_scope = &then_scope.base;
    ScopeLocalVal payload_val_scope;
    memset(&payload_val_scope, 0, sizeof(payload_val_scope));

    if (payload_has_scope) {
        payload_val_scope = (ScopeLocalVal) {
            .base = { .tag = SCOPE_LOCAL_VAL },
            .parent = &then_scope.base,
            .gen_zir = &then_scope,
            .inst = payload_ref,
            .token_src = payload_ident_token,
            .name = payload_ident_name,
        };
        dbg_var_name = payload_ident_name;
        dbg_var_inst = payload_ref;
        then_sub_scope = &payload_val_scope.base;
    }

    // Add payload instruction to then_scope (AstGen.zig:6714-6716).
    if (opt_payload_raw_inst != UINT32_MAX)
        gzAppendInstruction(&then_scope, opt_payload_raw_inst);
    // Add dbg_var_val for payload (AstGen.zig:6717).
    if (dbg_var_name != 0)
        addDbgVar(
            &then_scope, ZIR_INST_DBG_VAR_VAL, dbg_var_name, dbg_var_inst);
    // Add continue_block to then_scope (AstGen.zig:6718).
    gzAppendInstruction(&then_scope, continue_block_inst);

    // Emit continue expression if present (AstGen.zig:6723-6725).
    // Upstream: unusedResultExpr = emitDbgNode + expr + addEnsureResult.
    if (cont_expr != 0) {
        emitDbgNode(&then_scope, cont_expr);
        uint32_t cont_result = expr(&then_scope, then_sub_scope, cont_expr);
        addEnsureResult(&then_scope, cont_result, cont_expr);
    }

    // Create continue_scope (AstGen.zig:6692-6694, 6727).
    GenZir continue_scope = makeSubBlock(gz, then_sub_scope);

    // Execute body (AstGen.zig:6728-6731).
    uint32_t then_node = body_node;
    emitDbgNode(&continue_scope, then_node);
    uint32_t unused_result = fullBodyExpr(
        &continue_scope, &continue_scope.base, RL_NONE_VAL, then_node);
    addEnsureResult(&continue_scope, unused_result, then_node);

    // Break continue_block if not noreturn (AstGen.zig:6735-6747).
    ZirInstTag break_tag = is_inline ? ZIR_INST_BREAK_INLINE : ZIR_INST_BREAK;
    if (!endsWithNoReturn(&continue_scope)) {
        // dbg_stmt + dbg_empty_stmt (AstGen.zig:6736-6745).
        advanceSourceCursor(
            ag, tree->tokens.starts[lastToken(tree, then_node)]);
        emitDbgStmt(gz, ag->source_line - gz->decl_line, ag->source_column);
        {
            ZirInstData ext_data;
            ext_data.extended.opcode = (uint16_t)ZIR_EXT_DBG_EMPTY_STMT;
            ext_data.extended.small = 0;
            ext_data.extended.operand = 0;
            addInstruction(gz, ZIR_INST_EXTENDED, ext_data);
        }
        addBreak(&continue_scope, break_tag, continue_block_inst,
            ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
    }
    setBlockBody(ag, &continue_scope, continue_block_inst);
    // Break cond_block from then_scope (AstGen.zig:6749).
    addBreak(&then_scope, break_tag, cond_block, ZIR_REF_VOID_VALUE,
        AST_NODE_OFFSET_NONE);

    // Else scope (AstGen.zig:6751-6797).
    GenZir else_scope = makeSubBlock(gz, &cond_scope.base);

    if (else_node != 0) {
        Scope* else_sub_scope = &else_scope.base;
        ScopeLocalVal error_val_scope;
        memset(&error_val_scope, 0, sizeof(error_val_scope));

        if (error_token != 0) {
            // Error capture: else |err| (AstGen.zig:6756-6776).
            ZirInstTag err_tag = payload_is_ref ? ZIR_INST_ERR_UNION_CODE_PTR
                                                : ZIR_INST_ERR_UNION_CODE;
            uint32_t err_inst
                = addUnNode(&else_scope, err_tag, cond_inst, cond_node);
            if (tokenIsUnderscore(tree, error_token)) {
                // Discard |_| — else_sub_scope stays as &else_scope.base
            } else {
                uint32_t err_name = identAsString(ag, error_token);
                error_val_scope = (ScopeLocalVal) {
                    .base = { .tag = SCOPE_LOCAL_VAL },
                    .parent = &else_scope.base,
                    .gen_zir = &else_scope,
                    .inst = err_inst,
                    .token_src = error_token,
                    .name = err_name,
                };
                addDbgVar(
                    &else_scope, ZIR_INST_DBG_VAR_VAL, err_name, err_inst);
                else_sub_scope = &error_val_scope.base;
            }
        }

        // Remove continue/break blocks so control flow applies to outer
        // loops (AstGen.zig:6783-6784).
        loop_scope.continue_block = UINT32_MAX;
        loop_scope.break_block = UINT32_MAX;
        uint32_t else_result = fullBodyExpr(&else_scope, else_sub_scope,
            loop_scope.break_result_info, else_node);
        if (is_statement) {
            addEnsureResult(&else_scope, else_result, else_node);
        }
        if (!endsWithNoReturn(&else_scope)) {
            addBreak(&else_scope, break_tag, loop_inst, else_result,
                (int32_t)else_node - (int32_t)gz->decl_node_index);
        }
    } else {
        // No else: break with void (AstGen.zig:6794-6796).
        uint32_t void_result
            = rvalue(&else_scope, rl, ZIR_REF_VOID_VALUE, node);
        addBreak(&else_scope, break_tag, loop_inst, void_result,
            AST_NODE_OFFSET_NONE);
    }

    // Wire up condbr (AstGen.zig:6805).
    setCondBrPayload(ag, condbr, bool_bit, &then_scope, &else_scope);

    // Apply rvalue if needed (AstGen.zig:6807-6810).
    uint32_t result;
    if (need_result_rvalue)
        result = rvalue(gz, rl, loop_inst + ZIR_REF_START_INDEX, node);
    else
        result = loop_inst + ZIR_REF_START_INDEX;

    // Emit ensure_result_used when used as statement (AstGen.zig:6812-6814).
    if (is_statement) {
        addUnNode(gz, ZIR_INST_ENSURE_RESULT_USED, result, node);
    }

    return result;
}

// --- switchExpr (AstGen.zig:7625-8117) ---
// Handles switch and switch_comma expressions.
// Encoding: switch_block pl_node with SwitchBlock extra payload.

// Helper: append body instruction with ref_table fixups to pay buffer.
// Mirrors appendPossiblyRefdBodyInst (AstGen.zig:13675-13683) but writes
// to a dynamically-grown pay buffer instead of extra.
static void appendPossiblyRefdBodyInstPay(AstGenCtx* ag, uint32_t body_inst,
    uint32_t** pay, uint32_t* pay_len, uint32_t* pay_cap) {
    if (*pay_len >= *pay_cap) {
        *pay_cap *= 2;
        uint32_t* p = realloc(*pay, *pay_cap * sizeof(uint32_t));
        if (!p)
            abort();
        *pay = p;
    }
    (*pay)[(*pay_len)++] = body_inst;
    uint32_t ref_inst;
    if (refTableFetchRemove(ag, body_inst, &ref_inst)) {
        appendPossiblyRefdBodyInstPay(ag, ref_inst, pay, pay_len, pay_cap);
    }
}

// Helper: append body with fixups and extra refs to pay buffer.
// Mirrors appendBodyWithFixupsExtraRefsArrayList (AstGen.zig:13659-13673).
static void appendBodyWithFixupsExtraRefsPay(AstGenCtx* ag,
    const uint32_t* body, uint32_t body_len, const uint32_t* extra_refs,
    uint32_t extra_refs_len, uint32_t** pay, uint32_t* pay_len_p,
    uint32_t* pay_cap_p) {
    for (uint32_t i = 0; i < extra_refs_len; i++) {
        uint32_t ref_inst;
        if (refTableFetchRemove(ag, extra_refs[i], &ref_inst)) {
            appendPossiblyRefdBodyInstPay(
                ag, ref_inst, pay, pay_len_p, pay_cap_p);
        }
    }
    for (uint32_t i = 0; i < body_len; i++) {
        appendPossiblyRefdBodyInstPay(ag, body[i], pay, pay_len_p, pay_cap_p);
    }
}

// Helper: ensure pay buffer has capacity for `additional` more entries.
static void ensurePayCapacity(
    uint32_t** pay, uint32_t* pay_cap, uint32_t pay_len, uint32_t additional) {
    uint32_t needed = pay_len + additional;
    if (needed > *pay_cap) {
        while (*pay_cap < needed)
            *pay_cap *= 2;
        uint32_t* p = realloc(*pay, *pay_cap * sizeof(uint32_t));
        if (!p)
            abort();
        *pay = p;
    }
}

// Helper: get values for a switch case node. For SWITCH_CASE_ONE /
// SWITCH_CASE_INLINE_ONE, returns the single value (or NULL if else).
// For SWITCH_CASE / SWITCH_CASE_INLINE, returns the SubRange values.
// Returns values count and sets *values_arr to point to the values.
// For _ONE variants, writes to single_buf and returns pointer to it.
static uint32_t switchCaseValues(const Ast* tree, uint32_t case_node,
    uint32_t* single_buf, const uint32_t** values_arr) {
    AstNodeTag ct = tree->nodes.tags[case_node];
    AstData cd = tree->nodes.datas[case_node];
    switch (ct) {
    case AST_NODE_SWITCH_CASE_ONE:
    case AST_NODE_SWITCH_CASE_INLINE_ONE:
        if (cd.lhs == 0) {
            *values_arr = NULL;
            return 0; // else prong
        }
        *single_buf = cd.lhs;
        *values_arr = single_buf;
        return 1;
    case AST_NODE_SWITCH_CASE:
    case AST_NODE_SWITCH_CASE_INLINE: {
        uint32_t ist = tree->extra_data.arr[cd.lhs];
        uint32_t ien = tree->extra_data.arr[cd.lhs + 1];
        *values_arr = tree->extra_data.arr + ist;
        return ien - ist;
    }
    default:
        *values_arr = NULL;
        return 0;
    }
}

// --- switchExprErrUnion (AstGen.zig:7127-7623) ---
// Handles `catch |err| switch(err) { ... }` and
// `if (x) |v| { ... } else |err| switch (err) { ... }` optimization.
// Emits ZIR_INST_SWITCH_BLOCK_ERR_UNION instead of separate catch/if + switch.
// node_ty: 0=catch, 1=if.
static uint32_t switchExprErrUnion(GenZir* parent_gz, Scope* scope,
    ResultLoc rl, uint32_t catch_or_if_node, int node_ty) {
    AstGenCtx* ag = parent_gz->astgen;
    const Ast* tree = ag->tree;
    AstData cnd = tree->nodes.datas[catch_or_if_node];

    // Extract switch_node, operand_node, error_payload based on node_ty
    // (AstGen.zig:7138-7154).
    uint32_t switch_node, operand_node, error_payload;
    // For `if` case, we also need payload_token and then_node.
    uint32_t if_payload_token = 0; // 0 = no payload
    uint32_t if_then_node = 0;
    if (node_ty == 0) {
        // catch: rhs=switch, lhs=operand, main_token=catch keyword
        switch_node = cnd.rhs;
        operand_node = cnd.lhs;
        uint32_t catch_token = tree->nodes.main_tokens[catch_or_if_node];
        error_payload = catch_token + 2; // token after `catch |`
    } else {
        // if: parse fullIf structure (AstGen.zig:7138-7154).
        operand_node = cnd.lhs;
        if_then_node = tree->extra_data.arr[cnd.rhs];
        uint32_t else_node = tree->extra_data.arr[cnd.rhs + 1];
        switch_node = else_node;
        // Compute error_token.
        uint32_t else_tok = lastToken(tree, if_then_node) + 1;
        error_payload = else_tok + 2; // else |err| => err is at else_tok+2
        // Compute payload_token (if (cond) |val|).
        uint32_t last_cond_tok = lastToken(tree, operand_node);
        uint32_t pipe_tok = last_cond_tok + 2;
        if (pipe_tok < tree->tokens.len
            && tree->tokens.tags[pipe_tok] == TOKEN_PIPE) {
            if_payload_token = pipe_tok + 1;
        }
    }

    // Parse switch: lhs=condition, rhs=extra index for SubRange.
    AstData snd = tree->nodes.datas[switch_node];
    uint32_t sw_extra = snd.rhs;
    uint32_t cases_start = tree->extra_data.arr[sw_extra];
    uint32_t cases_end = tree->extra_data.arr[sw_extra + 1];
    const uint32_t* case_nodes_arr = tree->extra_data.arr + cases_start;
    uint32_t case_count = cases_end - cases_start;

    bool do_err_trace = (ag->fn_ret_ty != 0);
    bool need_rl = nodesNeedRlContains(ag, catch_or_if_node);
    ResultLoc break_rl
        = breakResultInfo(parent_gz, rl, catch_or_if_node, need_rl);
    bool need_result_rvalue = (break_rl.tag != rl.tag);

    // payload_is_ref (AstGen.zig:7168-7171).
    bool payload_is_ref;
    if (node_ty == 1) {
        payload_is_ref = (if_payload_token != 0
            && tree->tokens.tags[if_payload_token] == TOKEN_ASTERISK);
    } else {
        payload_is_ref = (rl.tag == RL_REF || rl.tag == RL_REF_COERCED_TY);
    }

    // First pass: categorize cases (AstGen.zig:7173-7229).
    uint32_t scalar_cases_len = 0;
    uint32_t multi_cases_len = 0;
    bool has_else = false;
    uint32_t else_ci = UINT32_MAX; // index into case_nodes_arr

    for (uint32_t ci = 0; ci < case_count; ci++) {
        uint32_t cn = case_nodes_arr[ci];
        uint32_t single_buf;
        const uint32_t* values;
        uint32_t values_len = switchCaseValues(tree, cn, &single_buf, &values);

        if (values_len == 0) {
            has_else = true;
            else_ci = ci;
            continue;
        }

        if (values_len == 1
            && tree->nodes.tags[values[0]] != AST_NODE_SWITCH_RANGE) {
            scalar_cases_len++;
        } else {
            multi_cases_len++;
        }
    }

    // Operand rl (AstGen.zig:7231-7234).
    ResultLoc operand_rl = payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;
    operand_rl.ctx = RI_CTX_ERROR_HANDLING_EXPR;

    // Save operand source location (AstGen.zig:7236-7237).
    advanceSourceCursorToNode(ag, operand_node);
    uint32_t operand_lc_line = ag->source_line - parent_gz->decl_line;
    uint32_t operand_lc_col = ag->source_column;

    uint32_t raw_operand = reachableExpr(
        parent_gz, scope, operand_rl, operand_node, switch_node);

    // --- Payload buffer ---
    // Table: [non_error_prong] [else?] [scalar_0..N] [multi_0..N]
    uint32_t case_table_start = 0;
    uint32_t scalar_case_table = case_table_start + 1 + (has_else ? 1u : 0u);
    uint32_t multi_case_table = scalar_case_table + scalar_cases_len;
    uint32_t case_table_end = multi_case_table + multi_cases_len;

    uint32_t pay_cap = case_table_end + case_count * 16;
    if (pay_cap < 64)
        pay_cap = 64;
    uint32_t* pay = malloc(pay_cap * sizeof(uint32_t));
    if (!pay)
        abort();
    uint32_t pay_len = case_table_end;

    GenZir block_scope = makeSubBlock(parent_gz, scope);
    block_scope.instructions_top = UINT32_MAX; // unstacked
    block_scope.break_result_info = break_rl;

    // dbg_stmt before switch_block_err_union (AstGen.zig:7249).
    emitDbgStmtForceCurrentIndex(parent_gz, operand_lc_line, operand_lc_col);

    uint32_t switch_inst = makeBlockInst(
        ag, ZIR_INST_SWITCH_BLOCK_ERR_UNION, parent_gz, switch_node);

    GenZir case_scope = makeSubBlock(parent_gz, &block_scope.base);

    // --- Non-error prong (AstGen.zig:7255-7391) ---
    {
        uint32_t body_len_index = pay_len;
        pay[case_table_start] = body_len_index;
        ensurePayCapacity(&pay, &pay_cap, pay_len, 1);
        pay_len = body_len_index + 1; // body_len slot

        case_scope.instructions_top = ag->scratch_inst_len;

        ZirInstTag unwrap_tag = payload_is_ref
            ? ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE_PTR
            : ZIR_INST_ERR_UNION_PAYLOAD_UNSAFE;
        uint32_t unwrapped = addUnNode(
            &case_scope, unwrap_tag, raw_operand, catch_or_if_node);

        if (node_ty == 0) {
            // catch: rvalue the unwrapped payload and break
            // (AstGen.zig:7299-7314).
            uint32_t case_result
                = (rl.tag == RL_REF || rl.tag == RL_REF_COERCED_TY)
                ? unwrapped
                : rvalue(&case_scope, block_scope.break_result_info, unwrapped,
                      catch_or_if_node);
            addBreak(&case_scope, ZIR_INST_BREAK, switch_inst, case_result,
                (int32_t)catch_or_if_node
                    - (int32_t)parent_gz->decl_node_index);
        } else {
            // if: evaluate then branch with payload capture
            // (AstGen.zig:7316-7368).
            ScopeLocalVal payload_val_scope;
            memset(&payload_val_scope, 0, sizeof(payload_val_scope));
            Scope* then_sub_scope = &case_scope.base;

            if (if_payload_token != 0) {
                uint32_t name_token
                    = if_payload_token + (payload_is_ref ? 1u : 0u);
                uint32_t ident_name = identAsString(ag, name_token);
                if (tokenIsUnderscore(tree, name_token)) {
                    // Discard: sub_scope stays as case_scope.
                } else {
                    payload_val_scope = (ScopeLocalVal) {
                        .base = { .tag = SCOPE_LOCAL_VAL },
                        .parent = &case_scope.base,
                        .gen_zir = &case_scope,
                        .name = ident_name,
                        .inst = unwrapped,
                        .token_src = name_token,
                    };
                    addDbgVar(&case_scope, ZIR_INST_DBG_VAR_VAL, ident_name,
                        unwrapped);
                    then_sub_scope = &payload_val_scope.base;
                }
            } else {
                // No payload: ensure payload is void
                // (AstGen.zig:7346-7350).
                addUnNode(&case_scope, ZIR_INST_ENSURE_ERR_UNION_PAYLOAD_VOID,
                    raw_operand, catch_or_if_node);
            }

            uint32_t then_result = exprRl(&case_scope, then_sub_scope,
                block_scope.break_result_info, if_then_node);
            if (!refIsNoReturn(parent_gz, then_result)) {
                addBreak(&case_scope, ZIR_INST_BREAK, switch_inst, then_result,
                    (int32_t)if_then_node
                        - (int32_t)parent_gz->decl_node_index);
            }
        }

        uint32_t raw_body_len = gzInstructionsLen(&case_scope);
        const uint32_t* body = gzInstructionsSlice(&case_scope);
        const uint32_t extra_refs[1] = { switch_inst };
        uint32_t body_len = countBodyLenAfterFixupsExtraRefs(
            ag, body, raw_body_len, extra_refs, 1);

        // ProngInfo: body_len, capture, not inline, no tag
        // (AstGen.zig:7375-7389).
        uint32_t capture = 0; // none
        if (node_ty == 1 && if_payload_token != 0) {
            capture = payload_is_ref ? 2u : 1u; // by_ref or by_val
        }
        pay[body_len_index]
            = (body_len & 0x0FFFFFFFu) | ((capture & 3u) << 28);

        ensurePayCapacity(&pay, &pay_cap, pay_len, body_len);
        appendBodyWithFixupsExtraRefsPay(
            ag, body, raw_body_len, extra_refs, 1, &pay, &pay_len, &pay_cap);

        gzUnstack(&case_scope);
    }

    // --- Error capture name (AstGen.zig:7329-7342) ---
    uint32_t err_name = identAsString(ag, error_payload);

    // Allocate shared value_placeholder for error capture
    // (AstGen.zig:7345-7353).
    uint32_t err_inst = ag->inst_len;
    ensureInstCapacity(ag, 1);
    ag->inst_tags[err_inst] = ZIR_INST_EXTENDED;
    ZirInstData edata;
    memset(&edata, 0xaa, sizeof(edata));
    edata.extended.opcode = (uint16_t)ZIR_EXT_VALUE_PLACEHOLDER;
    ag->inst_datas[err_inst] = edata;
    ag->inst_len++;

    // --- Error cases (AstGen.zig:7356-7520) ---
    uint32_t multi_case_index = 0;
    uint32_t scalar_case_index = 0;
    bool any_uses_err_capture = false;

    for (uint32_t ci = 0; ci < case_count; ci++) {
        uint32_t cn = case_nodes_arr[ci];
        AstNodeTag ct = tree->nodes.tags[cn];
        AstData cd = tree->nodes.datas[cn];
        bool is_inline = (ct == AST_NODE_SWITCH_CASE_INLINE_ONE
            || ct == AST_NODE_SWITCH_CASE_INLINE);

        uint32_t single_buf;
        const uint32_t* values;
        uint32_t values_len = switchCaseValues(tree, cn, &single_buf, &values);

        bool is_multi_case = values_len > 1
            || (values_len == 1
                && tree->nodes.tags[values[0]] == AST_NODE_SWITCH_RANGE);

        // Set up error capture scope (AstGen.zig:7366-7404).
        uint32_t dbg_var_name = 0;
        uint32_t dbg_var_inst = 0;
        ScopeLocalVal err_scope;
        ScopeLocalVal capture_scope_val;
        memset(&err_scope, 0, sizeof(err_scope));
        memset(&capture_scope_val, 0, sizeof(capture_scope_val));

        err_scope = (ScopeLocalVal) {
            .base = { .tag = SCOPE_LOCAL_VAL },
            .parent = &case_scope.base,
            .gen_zir = &case_scope,
            .inst = err_inst + ZIR_REF_START_INDEX,
            .token_src = error_payload,
            .name = err_name,
        };

        Scope* sub_scope = &err_scope.base;

        // Check for case payload capture (AstGen.zig:7381-7404).
        uint32_t arrow_token = tree->nodes.main_tokens[cn];
        bool has_payload = false;
        if (tree->tokens.tags[arrow_token + 1] == TOKEN_PIPE) {
            uint32_t capture_token = arrow_token + 2;
            if (tree->tokens.tags[capture_token] == TOKEN_IDENTIFIER) {
                has_payload = true;
                if (!tokenIsUnderscore(tree, capture_token)) {
                    uint32_t tag_name = identAsString(ag, capture_token);
                    capture_scope_val = (ScopeLocalVal) {
                        .base = { .tag = SCOPE_LOCAL_VAL },
                        .parent = &case_scope.base,
                        .gen_zir = &case_scope,
                        .inst = switch_inst + ZIR_REF_START_INDEX,
                        .token_src = capture_token,
                        .name = tag_name,
                    };
                    dbg_var_name = tag_name;
                    dbg_var_inst = switch_inst + ZIR_REF_START_INDEX;
                    // err_scope parent points to capture_scope_val
                    err_scope.parent = &capture_scope_val.base;
                }
            }
        }

        // Fill item data in pay buffer (AstGen.zig:7406-7462).
        ensurePayCapacity(&pay, &pay_cap, pay_len, 32);
        uint32_t hdr = pay_len;
        uint32_t prong_info_slot = 0;

        if (is_multi_case) {
            pay[multi_case_table + multi_case_index] = hdr;
            multi_case_index++;
            pay[pay_len++] = 0; // items_len placeholder
            pay[pay_len++] = 0; // ranges_len placeholder
            prong_info_slot = pay_len++;

            uint32_t nitems = 0;
            uint32_t nranges = 0;
            for (uint32_t vi = 0; vi < values_len; vi++) {
                if (tree->nodes.tags[values[vi]] == AST_NODE_SWITCH_RANGE) {
                    nranges++;
                    continue;
                }
                nitems++;
                ensurePayCapacity(&pay, &pay_cap, pay_len, 1);
                pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                    values[vi], COMPTIME_REASON_SWITCH_ITEM);
            }
            for (uint32_t vi = 0; vi < values_len; vi++) {
                if (tree->nodes.tags[values[vi]] != AST_NODE_SWITCH_RANGE)
                    continue;
                AstData rng = tree->nodes.datas[values[vi]];
                ensurePayCapacity(&pay, &pay_cap, pay_len, 2);
                pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                    rng.lhs, COMPTIME_REASON_SWITCH_ITEM);
                pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                    rng.rhs, COMPTIME_REASON_SWITCH_ITEM);
            }
            pay[hdr] = nitems;
            pay[hdr + 1] = nranges;
        } else if (ci == else_ci) {
            pay[case_table_start + 1] = hdr;
            prong_info_slot = pay_len++;
        } else {
            // Scalar case.
            pay[scalar_case_table + scalar_case_index] = hdr;
            scalar_case_index++;
            pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                values[0], COMPTIME_REASON_SWITCH_ITEM);
            prong_info_slot = pay_len++;
        }

        // Evaluate body (AstGen.zig:7464-7518).
        {
            case_scope.instructions_top = ag->scratch_inst_len;

            if (do_err_trace && nodeMayAppendToErrorTrace(tree, operand_node))
                addSaveErrRetIndex(&case_scope, ZIR_REF_NONE);

            if (dbg_var_name != 0) {
                addDbgVar(&case_scope, ZIR_INST_DBG_VAR_VAL, dbg_var_name,
                    dbg_var_inst);
            }

            uint32_t body_node = cd.rhs;
            uint32_t result = fullBodyExpr(&case_scope, sub_scope,
                block_scope.break_result_info, body_node);

            // Track err capture usage (AstGen.zig:7489-7494).
            // The upstream tracks scope usage via used/discarded fields.
            // We approximate: err capture is "used" if the err_scope was
            // found during identifier lookup (i.e., the err name was
            // referenced in the body). Since we don't track scope usage
            // in C, we check if any instruction in the body references
            // the err_inst placeholder.
            bool uses_err = false;
            {
                uint32_t rbl = gzInstructionsLen(&case_scope);
                const uint32_t* rbody = gzInstructionsSlice(&case_scope);
                for (uint32_t bi = 0; bi < rbl; bi++) {
                    uint32_t inst = rbody[bi];
                    // Check if any instruction data references err_inst.
                    ZirInstData d = ag->inst_datas[inst];
                    if (d.un_node.operand == err_inst + ZIR_REF_START_INDEX) {
                        uses_err = true;
                        break;
                    }
                }
            }
            if (uses_err) {
                addDbgVar(&case_scope, ZIR_INST_DBG_VAR_VAL, err_name,
                    err_inst + ZIR_REF_START_INDEX);
                any_uses_err_capture = true;
            }

            if (!refIsNoReturn(parent_gz, result)) {
                if (do_err_trace)
                    restoreErrRetIndex(&case_scope, switch_inst,
                        block_scope.break_result_info, body_node, result);
                addBreak(&case_scope, ZIR_INST_BREAK, switch_inst, result,
                    (int32_t)body_node - (int32_t)parent_gz->decl_node_index);
            }

            uint32_t raw_body_len = gzInstructionsLen(&case_scope);
            const uint32_t* body = gzInstructionsSlice(&case_scope);

            uint32_t extra_refs[2];
            uint32_t extra_refs_len = 0;
            extra_refs[extra_refs_len++] = switch_inst;
            if (uses_err)
                extra_refs[extra_refs_len++] = err_inst;

            uint32_t body_len = countBodyLenAfterFixupsExtraRefs(
                ag, body, raw_body_len, extra_refs, extra_refs_len);

            uint32_t capture = has_payload ? 1u : 0u; // by_val or none
            uint32_t prong_info = (body_len & 0x0FFFFFFFu)
                | ((capture & 3u) << 28) | ((is_inline ? 1u : 0u) << 30);
            pay[prong_info_slot] = prong_info;

            ensurePayCapacity(&pay, &pay_cap, pay_len, body_len);
            appendBodyWithFixupsExtraRefsPay(ag, body, raw_body_len,
                extra_refs, extra_refs_len, &pay, &pay_len, &pay_cap);

            gzUnstack(&case_scope);
        }
    }

    // Now add switch_inst to parent (AstGen.zig:7522).
    gzAppendInstruction(parent_gz, switch_inst);

    // --- Serialize to extra (AstGen.zig:7524-7615) ---
    ensureExtraCapacity(ag,
        3 + (multi_cases_len > 0 ? 1u : 0u) + (any_uses_err_capture ? 1u : 0u)
            + pay_len - case_table_end);
    uint32_t payload_index = ag->extra_len;

    // SwitchBlockErrUnion: operand (AstGen.zig:7529).
    ag->extra[ag->extra_len++] = raw_operand;

    // SwitchBlockErrUnion: bits (AstGen.zig:7530-7538).
    {
        uint32_t bits = 0;
        if (multi_cases_len > 0)
            bits |= 1u; // has_multi_cases (bit 0)
        if (has_else)
            bits |= (1u << 1); // has_else (bit 1)
        if (any_uses_err_capture)
            bits |= (1u << 2); // any_uses_err_capture (bit 2)
        if (payload_is_ref)
            bits |= (1u << 3); // payload_is_ref (bit 3)
        bits |= (scalar_cases_len & 0x0FFFFFFFu) << 4; // scalar_cases_len
        ag->extra[ag->extra_len++] = bits;
    }

    // SwitchBlockErrUnion: main_src_node_offset (AstGen.zig:7539).
    ag->extra[ag->extra_len++] = (uint32_t)((int32_t)catch_or_if_node
        - (int32_t)parent_gz->decl_node_index);

    // multi_cases_len (AstGen.zig:7542-7544).
    if (multi_cases_len > 0)
        ag->extra[ag->extra_len++] = multi_cases_len;

    // err_inst (AstGen.zig:7546-7548).
    if (any_uses_err_capture)
        ag->extra[ag->extra_len++] = err_inst;

    ag->inst_datas[switch_inst].pl_node.payload_index = payload_index;

    // Serialize case data from pay table (AstGen.zig:7552-7613).
    for (uint32_t i = 0; i < case_table_end; i++) {
        uint32_t si = pay[i];
        uint32_t body_len_idx = si;
        uint32_t end = si;

        if (i < scalar_case_table) {
            // Non-error or else prong: [prong_info, body...]
            end += 1;
        } else if (i < multi_case_table) {
            // Scalar: [item, prong_info, body...]
            body_len_idx = si + 1;
            end += 2;
        } else {
            // Multi: [items_len, ranges_len, prong_info, items..., ranges...]
            body_len_idx = si + 2;
            uint32_t ni = pay[si];
            uint32_t nr = pay[si + 1];
            end += 3 + ni + nr * 2;
        }
        uint32_t prong_info = pay[body_len_idx];
        uint32_t bl = prong_info & 0x0FFFFFFFu;
        end += bl;
        ensureExtraCapacity(ag, end - si);
        for (uint32_t j = si; j < end; j++)
            ag->extra[ag->extra_len++] = pay[j];
    }

    free(pay);

    if (need_result_rvalue)
        return rvalue(
            parent_gz, rl, switch_inst + ZIR_REF_START_INDEX, switch_node);
    return switch_inst + ZIR_REF_START_INDEX;
}

static uint32_t switchExpr(
    GenZir* parent_gz, Scope* scope, ResultLoc rl, uint32_t node) {
    AstGenCtx* ag = parent_gz->astgen;
    const Ast* tree = ag->tree;
    bool need_rl = nodesNeedRlContains(ag, node);
    ResultLoc break_rl = breakResultInfo(parent_gz, rl, node, need_rl);
    AstData nd = tree->nodes.datas[node];

    // Detect label (AstGen.zig:7652-7654 / Ast.zig switchFull).
    uint32_t main_token = tree->nodes.main_tokens[node];
    uint32_t label_token = UINT32_MAX; // none
    if (tree->tokens.tags[main_token] == TOKEN_IDENTIFIER) {
        label_token = main_token;
        // switch_token = main_token + 2 (skip label + colon)
    }

    // AST_NODE_SWITCH: lhs = condition node, rhs = extra index for SubRange.
    // SubRange[rhs] = { cases_start, cases_end }.
    // Case nodes are at extra_data[cases_start..cases_end].
    uint32_t cond_node = nd.lhs;
    uint32_t extra_idx = nd.rhs;
    uint32_t cases_start = tree->extra_data.arr[extra_idx];
    uint32_t cases_end = tree->extra_data.arr[extra_idx + 1];
    const uint32_t* case_nodes_arr = tree->extra_data.arr + cases_start;
    uint32_t case_count = cases_end - cases_start;

    // --- First pass: categorize cases (AstGen.zig:7659-7762) ---
    bool any_payload_is_ref = false;
    bool any_has_tag_capture = false;
    bool any_non_inline_capture = false;
    uint32_t scalar_cases_len = 0;
    uint32_t multi_cases_len = 0;
    bool has_else = false;
    // Underscore prong tracking (AstGen.zig:7667-7670).
    uint32_t underscore_case_idx = UINT32_MAX; // index into case_nodes_arr
    uint32_t underscore_node = UINT32_MAX; // the `_` value node
    // underscore_additional_items: 0=none, 2=under, 4=under_one_item,
    // 6=under_many_items (matching SpecialProngs bit patterns).
    uint32_t underscore_additional_items = 2; // .under

    for (uint32_t ci = 0; ci < case_count; ci++) {
        uint32_t cn = case_nodes_arr[ci];
        AstNodeTag ct = tree->nodes.tags[cn];
        AstData cd = tree->nodes.datas[cn];
        bool is_inline = (ct == AST_NODE_SWITCH_CASE_INLINE_ONE
            || ct == AST_NODE_SWITCH_CASE_INLINE);

        // Check payload token for ref/tag capture (AstGen.zig:7673-7689).
        uint32_t arrow_token = tree->nodes.main_tokens[cn]; // =>
        if (tree->tokens.tags[arrow_token + 1] == TOKEN_PIPE) {
            uint32_t payload_token = arrow_token + 2;
            uint32_t ident = payload_token;
            if (tree->tokens.tags[payload_token] == TOKEN_ASTERISK) {
                any_payload_is_ref = true;
                ident = payload_token + 1;
            }
            if (tree->tokens.tags[ident + 1] == TOKEN_COMMA) {
                any_has_tag_capture = true;
            }
            if (!tokenIsUnderscore(tree, ident)) {
                any_non_inline_capture = true;
            }
        }

        // Get values for this case.
        uint32_t single_buf;
        const uint32_t* values;
        uint32_t values_len = switchCaseValues(tree, cn, &single_buf, &values);

        // Check for else prong (values_len == 0) (AstGen.zig:7693-7711).
        if (values_len == 0) {
            has_else = true;
            continue;
        }

        // Check for '_' prong (AstGen.zig:7714-7752).
        bool case_has_underscore = false;
        for (uint32_t vi = 0; vi < values_len; vi++) {
            uint32_t val = values[vi];
            if (tree->nodes.tags[val] == AST_NODE_IDENTIFIER
                && isUnderscoreIdent(tree, val)) {
                underscore_case_idx = ci;
                underscore_node = val;
                switch (values_len) {
                case 1:
                    underscore_additional_items = 2; // .under
                    break;
                case 2:
                    underscore_additional_items = 4; // .under_one_item
                    break;
                default:
                    underscore_additional_items = 6; // .under_many_items
                    break;
                }
                case_has_underscore = true;
            }
        }
        if (case_has_underscore)
            continue;

        // Categorize as scalar or multi (AstGen.zig:7754-7758).
        if (values_len == 1
            && tree->nodes.tags[values[0]] != AST_NODE_SWITCH_RANGE) {
            scalar_cases_len++;
        } else {
            multi_cases_len++;
        }
        (void)is_inline; // inline_cases_len tracking skipped (issue 13)
        (void)cd;
    }

    // Compute special_prongs (AstGen.zig:7764-7770).
    // SpecialProngs is a 3-bit field:
    //   bit 0: has_else
    //   bits 1-2: underscore variant (0=none, 1=under, 2=under_one_item,
    //             3=under_many_items)
    bool has_under = (underscore_case_idx != UINT32_MAX);
    uint32_t special_prongs; // 3-bit SpecialProngs enum value
    {
        uint32_t else_bit = has_else ? 1u : 0u;
        uint32_t under_bits = has_under ? underscore_additional_items : 0u;
        special_prongs = else_bit | under_bits;
    }

    // Operand result info (AstGen.zig:7772).
    ResultLoc operand_ri = any_payload_is_ref ? RL_REF_VAL : RL_NONE_VAL;

    // Save operand source location before evaluating (AstGen.zig:7774-7775).
    advanceSourceCursorToNode(ag, cond_node);
    uint32_t operand_lc_line = ag->source_line - parent_gz->decl_line;
    uint32_t operand_lc_col = ag->source_column;

    // Evaluate switch operand (AstGen.zig:7777).
    uint32_t raw_operand = exprRl(parent_gz, scope, operand_ri, cond_node);

    // Compute typeof for labeled switch continue support
    // (AstGen.zig:7782-7784).
    uint32_t raw_operand_ty_ref = 0;
    if (label_token != UINT32_MAX) {
        raw_operand_ty_ref
            = addUnNode(parent_gz, ZIR_INST_TYPEOF, raw_operand, cond_node);
    }

    // Sema expects a dbg_stmt immediately before switch_block(_ref)
    // (AstGen.zig:7806).
    emitDbgStmtForceCurrentIndex(parent_gz, operand_lc_line, operand_lc_col);

    // Create switch_block instruction (AstGen.zig:7808-7809).
    ZirInstTag switch_tag = any_payload_is_ref ? ZIR_INST_SWITCH_BLOCK_REF
                                               : ZIR_INST_SWITCH_BLOCK;
    uint32_t switch_inst = makeBlockInst(ag, switch_tag, parent_gz, node);

    // Set up block_scope (AstGen.zig:7800-7826).
    GenZir block_scope = makeSubBlock(parent_gz, scope);
    block_scope.instructions_top = UINT32_MAX; // unstacked
    block_scope.break_result_info = break_rl;

    // Label support (AstGen.zig:7811-7826).
    if (label_token != UINT32_MAX) {
        block_scope.continue_block = switch_inst;
        // continue_result_info: for ref, use ref_coerced_ty; else coerced_ty
        // (AstGen.zig:7813-7818).
        if (any_payload_is_ref) {
            block_scope.break_result_info
                = (ResultLoc) { .tag = RL_REF_COERCED_TY,
                      .data = raw_operand_ty_ref,
                      .src_node = 0,
                      .ctx = RI_CTX_NONE };
        }
        // Note: we store continue_result_info as break_result_info on
        // block_scope for now; the label's block_inst is switch_inst.
        block_scope.label_token = label_token;
        block_scope.label_block_inst = switch_inst;
    }

    // Allocate shared value_placeholder for tag captures
    // (AstGen.zig:7833-7844).
    uint32_t tag_inst = 0;
    if (any_has_tag_capture) {
        tag_inst = ag->inst_len;
        ensureInstCapacity(ag, 1);
        ag->inst_tags[tag_inst] = ZIR_INST_EXTENDED;
        ZirInstData tdata;
        memset(&tdata, 0xaa, sizeof(tdata));
        tdata.extended.opcode = (uint16_t)ZIR_EXT_VALUE_PLACEHOLDER;
        ag->inst_datas[tag_inst] = tdata;
        ag->inst_len++;
    }

    // Case scope — re-used for all cases (AstGen.zig:7829-7830).
    GenZir case_scope = makeSubBlock(parent_gz, &block_scope.base);
    case_scope.instructions_top = UINT32_MAX; // unstacked initially

    // --- Payload buffer (AstGen.zig:7789-7798) ---
    // Table layout: [else?] [under?] [scalar_0..N] [multi_0..N]
    uint32_t else_tbl = 0;
    uint32_t under_tbl = (has_else ? 1u : 0u);
    uint32_t scalar_tbl = under_tbl + (has_under ? 1u : 0u);
    uint32_t multi_tbl = scalar_tbl + scalar_cases_len;
    uint32_t table_size = multi_tbl + multi_cases_len;

    uint32_t pay_cap = table_size + case_count * 16;
    if (pay_cap < 64)
        pay_cap = 64;
    uint32_t* pay = malloc(pay_cap * sizeof(uint32_t));
    uint32_t pay_len = table_size;

    uint32_t scalar_ci = 0;
    uint32_t multi_ci = 0;

    // --- Second pass: emit items and bodies (AstGen.zig:7849-8027) ---
    for (uint32_t ci = 0; ci < case_count; ci++) {
        uint32_t cn = case_nodes_arr[ci];
        AstNodeTag ct = tree->nodes.tags[cn];
        AstData cd = tree->nodes.datas[cn];
        bool is_inline = (ct == AST_NODE_SWITCH_CASE_INLINE_ONE
            || ct == AST_NODE_SWITCH_CASE_INLINE);

        // Get values for this case.
        uint32_t single_buf;
        const uint32_t* values;
        uint32_t values_len = switchCaseValues(tree, cn, &single_buf, &values);

        // Determine if this is the else, underscore, scalar, or multi case.
        bool is_else_case = (values_len == 0);
        bool is_underscore_case = (ci == underscore_case_idx);
        bool is_multi_case = false;
        if (!is_else_case && !is_underscore_case) {
            is_multi_case = (values_len > 1
                || (values_len == 1
                    && tree->nodes.tags[values[0]] == AST_NODE_SWITCH_RANGE));
        }

        // Parse payload token (AstGen.zig:7855-7921).
        uint32_t dbg_var_name = 0; // NullTerminatedString, 0 = empty
        uint32_t dbg_var_inst = 0;
        uint32_t dbg_var_tag_name = 0;
        uint32_t dbg_var_tag_inst = 0;
        bool has_tag_capture = false;
        ScopeLocalVal capture_val_scope;
        ScopeLocalVal tag_scope_val;
        memset(&capture_val_scope, 0, sizeof(capture_val_scope));
        memset(&tag_scope_val, 0, sizeof(tag_scope_val));

        uint32_t capture = 0; // 0=none, 1=by_val, 2=by_ref

        uint32_t arrow_token = tree->nodes.main_tokens[cn];
        bool has_payload = (tree->tokens.tags[arrow_token + 1] == TOKEN_PIPE);
        Scope* sub_scope = &case_scope.base;

        if (has_payload) {
            uint32_t payload_token = arrow_token + 2;
            bool capture_is_ref
                = (tree->tokens.tags[payload_token] == TOKEN_ASTERISK);
            uint32_t ident = payload_token + (capture_is_ref ? 1u : 0u);

            capture = capture_is_ref ? 2u : 1u; // by_ref : by_val

            if (tokenIsUnderscore(tree, ident)) {
                // Discard capture (AstGen.zig:7874-7878).
                if (capture_is_ref) {
                    SET_ERROR(ag);
                    free(pay);
                    return ZIR_REF_VOID_VALUE;
                }
                capture = 0; // none
                // sub_scope stays as &case_scope.base
            } else {
                // Named capture (AstGen.zig:7880-7892).
                uint32_t capture_name = identAsString(ag, ident);
                capture_val_scope = (ScopeLocalVal) {
                    .base = { .tag = SCOPE_LOCAL_VAL },
                    .parent = &case_scope.base,
                    .gen_zir = &case_scope,
                    .inst = switch_inst + ZIR_REF_START_INDEX,
                    .token_src = ident,
                    .name = capture_name,
                };
                dbg_var_name = capture_name;
                dbg_var_inst = switch_inst + ZIR_REF_START_INDEX;
                sub_scope = &capture_val_scope.base;
            }

            // Check for tag capture: ident followed by comma
            // (AstGen.zig:7895-7921).
            if (tree->tokens.tags[ident + 1] == TOKEN_COMMA) {
                uint32_t tag_token = ident + 2;
                uint32_t tag_name = identAsString(ag, tag_token);

                has_tag_capture = true;

                tag_scope_val = (ScopeLocalVal) {
                    .base = { .tag = SCOPE_LOCAL_VAL },
                    .parent = sub_scope,
                    .gen_zir = &case_scope,
                    .inst = tag_inst + ZIR_REF_START_INDEX,
                    .token_src = tag_token,
                    .name = tag_name,
                };
                dbg_var_tag_name = tag_name;
                dbg_var_tag_inst = tag_inst + ZIR_REF_START_INDEX;
                sub_scope = &tag_scope_val.base;
            }
        }

        ensurePayCapacity(&pay, &pay_cap, pay_len, 32);
        uint32_t hdr = pay_len;
        uint32_t prong_info_slot = 0;

        // Determine case kind and fill item data (AstGen.zig:7924-7995).
        if (is_underscore_case && is_multi_case) {
            // Underscore case with additional items as multi
            // (AstGen.zig:7926-7942).
            pay[under_tbl] = hdr;
            if (underscore_additional_items == 4) {
                // One additional item (AstGen.zig:7928-7937).
                // [item_ref, prong_info]
                uint32_t item_node;
                if (values[0] == underscore_node)
                    item_node = values[1];
                else
                    item_node = values[0];
                pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                    item_node, COMPTIME_REASON_SWITCH_ITEM);
                prong_info_slot = pay_len++;
            } else {
                // Many additional items: multi format
                // (AstGen.zig:7943-7977).
                uint32_t nitems = 0;
                uint32_t nranges = 0;
                for (uint32_t vi = 0; vi < values_len; vi++) {
                    if (values[vi] == underscore_node)
                        continue;
                    if (tree->nodes.tags[values[vi]] == AST_NODE_SWITCH_RANGE)
                        nranges++;
                    else
                        nitems++;
                }
                pay[pay_len++] = nitems;
                pay[pay_len++] = nranges;
                prong_info_slot = pay_len++;
                // Non-range items.
                for (uint32_t vi = 0; vi < values_len; vi++) {
                    if (values[vi] == underscore_node)
                        continue;
                    if (tree->nodes.tags[values[vi]]
                        != AST_NODE_SWITCH_RANGE) {
                        ensurePayCapacity(&pay, &pay_cap, pay_len, 1);
                        pay[pay_len++]
                            = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                                values[vi], COMPTIME_REASON_SWITCH_ITEM);
                    }
                }
                // Range pairs.
                for (uint32_t vi = 0; vi < values_len; vi++) {
                    if (values[vi] == underscore_node)
                        continue;
                    if (tree->nodes.tags[values[vi]]
                        == AST_NODE_SWITCH_RANGE) {
                        AstData rng = tree->nodes.datas[values[vi]];
                        ensurePayCapacity(&pay, &pay_cap, pay_len, 2);
                        pay[pay_len++] = comptimeExpr(parent_gz, scope,
                            RL_NONE_VAL, rng.lhs, COMPTIME_REASON_SWITCH_ITEM);
                        pay[pay_len++] = comptimeExpr(parent_gz, scope,
                            RL_NONE_VAL, rng.rhs, COMPTIME_REASON_SWITCH_ITEM);
                    }
                }
            }
        } else if (is_else_case) {
            // Else prong (AstGen.zig:7978-7981).
            pay[else_tbl] = hdr;
            prong_info_slot = pay_len++;
        } else if (is_underscore_case) {
            // Underscore-only prong, no additional items
            // (AstGen.zig:7982-7986).
            pay[under_tbl] = hdr;
            prong_info_slot = pay_len++;
        } else if (!is_multi_case) {
            // Scalar case (AstGen.zig:7987-7994).
            pay[scalar_tbl + scalar_ci++] = hdr;
            pay[pay_len++] = comptimeExpr(parent_gz, scope, RL_NONE_VAL,
                values[0], COMPTIME_REASON_SWITCH_ITEM);
            prong_info_slot = pay_len++;
        } else {
            // Multi case (AstGen.zig:7939-7977 non-underscore path).
            pay[multi_tbl + multi_ci++] = hdr;
            uint32_t nitems = 0;
            uint32_t nranges = 0;
            for (uint32_t vi = 0; vi < values_len; vi++) {
                if (tree->nodes.tags[values[vi]] == AST_NODE_SWITCH_RANGE)
                    nranges++;
                else
                    nitems++;
            }
            pay[pay_len++] = nitems;
            pay[pay_len++] = nranges;
            prong_info_slot = pay_len++;
            // Non-range items.
            for (uint32_t vi = 0; vi < values_len; vi++) {
                if (tree->nodes.tags[values[vi]] != AST_NODE_SWITCH_RANGE) {
                    ensurePayCapacity(&pay, &pay_cap, pay_len, 1);
                    pay[pay_len++] = comptimeExpr(parent_gz, scope,
                        RL_NONE_VAL, values[vi], COMPTIME_REASON_SWITCH_ITEM);
                }
            }
            // Range pairs.
            for (uint32_t vi = 0; vi < values_len; vi++) {
                if (tree->nodes.tags[values[vi]] == AST_NODE_SWITCH_RANGE) {
                    AstData rng = tree->nodes.datas[values[vi]];
                    ensurePayCapacity(&pay, &pay_cap, pay_len, 2);
                    pay[pay_len++] = comptimeExpr(parent_gz, scope,
                        RL_NONE_VAL, rng.lhs, COMPTIME_REASON_SWITCH_ITEM);
                    pay[pay_len++] = comptimeExpr(parent_gz, scope,
                        RL_NONE_VAL, rng.rhs, COMPTIME_REASON_SWITCH_ITEM);
                }
            }
        }

        // Evaluate body (AstGen.zig:7997-8026).
        {
            // Temporarily stack case_scope on parent_gz
            // (AstGen.zig:7998-8000).
            case_scope.instructions_top = parent_gz->astgen->scratch_inst_len;

            if (dbg_var_name != 0) {
                addDbgVar(&case_scope, ZIR_INST_DBG_VAR_VAL, dbg_var_name,
                    dbg_var_inst);
            }
            if (dbg_var_tag_name != 0) {
                addDbgVar(&case_scope, ZIR_INST_DBG_VAR_VAL, dbg_var_tag_name,
                    dbg_var_tag_inst);
            }

            uint32_t body_node = cd.rhs;
            uint32_t result = fullBodyExpr(&case_scope, sub_scope,
                block_scope.break_result_info, body_node);
            if (!refIsNoReturn(parent_gz, result)) {
                addBreak(&case_scope, ZIR_INST_BREAK, switch_inst, result,
                    (int32_t)body_node - (int32_t)parent_gz->decl_node_index);
            }

            uint32_t raw_body_len = gzInstructionsLen(&case_scope);
            const uint32_t* body = gzInstructionsSlice(&case_scope);

            // Body fixups with extra refs (AstGen.zig:8016-8025).
            uint32_t extra_refs[2];
            uint32_t extra_refs_len = 0;
            extra_refs[extra_refs_len++] = switch_inst;
            if (has_tag_capture) {
                extra_refs[extra_refs_len++] = tag_inst;
            }

            uint32_t body_len = countBodyLenAfterFixupsExtraRefs(
                ag, body, raw_body_len, extra_refs, extra_refs_len);

            // Encode ProngInfo (AstGen.zig:8019-8024).
            uint32_t prong_info = (body_len & 0x0FFFFFFFu)
                | ((capture & 3u) << 28) | ((is_inline ? 1u : 0u) << 30)
                | ((has_tag_capture ? 1u : 0u) << 31);
            pay[prong_info_slot] = prong_info;

            ensurePayCapacity(&pay, &pay_cap, pay_len, body_len);
            appendBodyWithFixupsExtraRefsPay(ag, body, raw_body_len,
                extra_refs, extra_refs_len, &pay, &pay_len, &pay_cap);

            gzUnstack(&case_scope);
        }
    }

    // Now add switch_block to parent (AstGen.zig:8034).
    gzAppendInstruction(parent_gz, switch_inst);

    // --- Serialize to extra in payload order (AstGen.zig:8036-8110) ---
    ensureExtraCapacity(ag,
        2 + (uint32_t)(multi_cases_len > 0 ? 1 : 0)
            + (any_has_tag_capture ? 1u : 0u) + pay_len - table_size);
    uint32_t payload_index = ag->extra_len;

    // SwitchBlock.operand (AstGen.zig:8042).
    ag->extra[ag->extra_len++] = raw_operand;

    // SwitchBlock.bits (AstGen.zig:8043-8050).
    {
        uint32_t bits = 0;
        if (multi_cases_len > 0)
            bits |= 1u; // has_multi_cases (bit 0)
        bits |= (special_prongs & 7u) << 1; // special_prongs (bits 1-3)
        if (any_has_tag_capture)
            bits |= (1u << 4); // any_has_tag_capture (bit 4)
        if (any_non_inline_capture)
            bits |= (1u << 5); // any_non_inline_capture (bit 5)
        // has_continue (bit 6): set if label used for continue.
        // We don't track used_for_continue precisely, so set it if label
        // exists (conservative). Skipping precise tracking per issue 9.
        // Actually: only set if label_token != UINT32_MAX.
        // The upstream checks block_scope.label.used_for_continue; we
        // don't track that, so conservatively set it when there's a label.
        // This is safe: sema handles the flag as an optimization hint.
        if (label_token != UINT32_MAX)
            bits |= (1u << 6); // has_continue
        bits |= (scalar_cases_len & 0x1FFFFFFu) << 7; // scalar_cases_len
        ag->extra[ag->extra_len++] = bits;
    }

    // multi_cases_len (AstGen.zig:8053-8055).
    if (multi_cases_len > 0)
        ag->extra[ag->extra_len++] = multi_cases_len;

    // tag_inst (AstGen.zig:8057-8059).
    if (any_has_tag_capture)
        ag->extra[ag->extra_len++] = tag_inst;

    ag->inst_datas[switch_inst].pl_node.payload_index = payload_index;

    // Else prong (AstGen.zig:8064-8070).
    if (has_else) {
        uint32_t si = pay[else_tbl];
        uint32_t prong_info = pay[si];
        uint32_t bl = prong_info & 0x0FFFFFFFu;
        uint32_t end = si + 1 + bl;
        for (uint32_t i = si; i < end; i++)
            ag->extra[ag->extra_len++] = pay[i];
    }

    // Underscore prong (AstGen.zig:8071-8093).
    if (has_under) {
        uint32_t si = pay[under_tbl];
        uint32_t body_len_idx = si;
        uint32_t end = si;
        switch (underscore_additional_items) {
        case 2: // none
            end += 1; // just prong_info
            break;
        case 4: // one additional item
            body_len_idx = si + 1;
            end += 2; // item + prong_info
            break;
        case 6: // many additional items
            body_len_idx = si + 2;
            end += 3 + pay[si] + 2 * pay[si + 1]; // hdr + items + ranges
            break;
        default:
            break;
        }
        uint32_t prong_info = pay[body_len_idx];
        uint32_t bl = prong_info & 0x0FFFFFFFu;
        end += bl;
        for (uint32_t i = si; i < end; i++)
            ag->extra[ag->extra_len++] = pay[i];
    }

    // Scalar and multi cases (AstGen.zig:8094-8110).
    for (uint32_t i = 0; i < scalar_cases_len + multi_cases_len; i++) {
        uint32_t tbl_idx = scalar_tbl + i;
        uint32_t si = pay[tbl_idx];
        uint32_t body_len_idx;
        uint32_t end = si;
        if (tbl_idx < multi_tbl) {
            // Scalar: [item, prong_info, body...]
            body_len_idx = si + 1;
            end += 2;
        } else {
            // Multi: [items_len, ranges_len, prong_info, items..., ranges...]
            body_len_idx = si + 2;
            uint32_t ni = pay[si];
            uint32_t nr = pay[si + 1];
            end += 3 + ni + nr * 2;
        }
        uint32_t prong_info = pay[body_len_idx];
        uint32_t bl = prong_info & 0x0FFFFFFFu;
        end += bl;
        for (uint32_t j = si; j < end; j++)
            ag->extra[ag->extra_len++] = pay[j];
    }

    free(pay);

    // AstGen.zig:8112-8115.
    bool need_result_rvalue = (break_rl.tag != rl.tag);
    if (need_result_rvalue)
        return rvalue(parent_gz, rl, switch_inst + ZIR_REF_START_INDEX, node);
    return switch_inst + ZIR_REF_START_INDEX;
}

// --- rvalue (AstGen.zig:11029) ---
// Simplified: handles .none and .discard result locations.

static uint32_t rvalueDiscard(GenZir* gz, uint32_t result, uint32_t src_node) {
    // .discard => emit ensure_result_non_error, return .void_value
    // (AstGen.zig:11071-11074)
    ZirInstData data;
    data.un_node.src_node = (int32_t)src_node - (int32_t)gz->decl_node_index;
    data.un_node.operand = result;
    addInstruction(gz, ZIR_INST_ENSURE_RESULT_NON_ERROR, data);
    return ZIR_REF_VOID_VALUE;
}

// --- emitDbgNode / emitDbgStmt (AstGen.zig:3422, 13713) ---

static void emitDbgStmt(GenZir* gz, uint32_t line, uint32_t column) {
    if (gz->is_comptime)
        return;
    // Check if last instruction is already dbg_stmt; if so, update it.
    // (AstGen.zig:13715-13724)
    AstGenCtx* ag = gz->astgen;
    uint32_t gz_len = gzInstructionsLen(gz);
    if (gz_len > 0) {
        uint32_t last = gzInstructionsSlice(gz)[gz_len - 1];
        if (ag->inst_tags[last] == ZIR_INST_DBG_STMT) {
            ag->inst_datas[last].dbg_stmt.line = line;
            ag->inst_datas[last].dbg_stmt.column = column;
            return;
        }
    }
    ZirInstData data;
    data.dbg_stmt.line = line;
    data.dbg_stmt.column = column;
    addInstruction(gz, ZIR_INST_DBG_STMT, data);
}

// Mirrors emitDbgStmtForceCurrentIndex (AstGen.zig:13739-13760).
static void emitDbgStmtForceCurrentIndex(
    GenZir* gz, uint32_t line, uint32_t column) {
    AstGenCtx* ag = gz->astgen;
    uint32_t gz_len = gzInstructionsLen(gz);
    if (gz_len > 0
        && gzInstructionsSlice(gz)[gz_len - 1] == ag->inst_len - 1) {
        uint32_t last = ag->inst_len - 1;
        if (ag->inst_tags[last] == ZIR_INST_DBG_STMT) {
            ag->inst_datas[last].dbg_stmt.line = line;
            ag->inst_datas[last].dbg_stmt.column = column;
            return;
        }
    }
    ZirInstData data;
    data.dbg_stmt.line = line;
    data.dbg_stmt.column = column;
    addInstruction(gz, ZIR_INST_DBG_STMT, data);
}

static void emitDbgNode(GenZir* gz, uint32_t node) {
    if (gz->is_comptime)
        return;
    AstGenCtx* ag = gz->astgen;
    advanceSourceCursorToNode(ag, node);
    uint32_t line = ag->source_line - gz->decl_line;
    uint32_t column = ag->source_column;
    emitDbgStmt(gz, line, column);
}

// --- assign (AstGen.zig:3434) ---
// Handles `_ = expr` discard pattern.

static void assignStmt(GenZir* gz, Scope* scope, uint32_t infix_node) {
    emitDbgNode(gz, infix_node);
    const AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    AstData nd = tree->nodes.datas[infix_node];
    uint32_t lhs = nd.lhs;
    uint32_t rhs = nd.rhs;

    // Check if LHS is `_` identifier for discard (AstGen.zig:3440-3446).
    if (tree->nodes.tags[lhs] == AST_NODE_IDENTIFIER) {
        uint32_t ident_tok = tree->nodes.main_tokens[lhs];
        uint32_t tok_start = tree->tokens.starts[ident_tok];
        if (tree->source[tok_start] == '_'
            && (tok_start + 1 >= tree->source_len
                || !((tree->source[tok_start + 1] >= 'a'
                         && tree->source[tok_start + 1] <= 'z')
                    || (tree->source[tok_start + 1] >= 'A'
                        && tree->source[tok_start + 1] <= 'Z')
                    || tree->source[tok_start + 1] == '_'
                    || (tree->source[tok_start + 1] >= '0'
                        && tree->source[tok_start + 1] <= '9')))) {
            // Discard: evaluate RHS with .discard result location.
            uint32_t result = expr(gz, scope, rhs);
            rvalueDiscard(gz, result, rhs);
            return;
        }
    }

    // Non-discard assignment: evaluate LHS as lvalue, pass ptr rl to RHS.
    // (AstGen.zig:3448-3452).
    {
        uint32_t lhs_ptr = exprRl(gz, scope, RL_REF_VAL, lhs);
        ResultLoc ptr_rl
            = { .tag = RL_PTR, .data = lhs_ptr, .src_node = infix_node };
        (void)exprRl(gz, scope, ptr_rl, rhs);
    }
}

// --- assignDestructure (AstGen.zig:3456-3504) ---
// Handles destructure assignments where LHS is only lvalue expressions (no
// new var/const declarations). Called from exprRl and blockExprStmts.

static void assignDestructure(GenZir* gz, Scope* scope, uint32_t node) {
    emitDbgNode(gz, node);
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    // Parse assign_destructure node: lhs=extra_index, rhs=value_expr.
    AstData nd = tree->nodes.datas[node];
    uint32_t extra_start = nd.lhs;
    uint32_t value_expr = nd.rhs;
    uint32_t variable_count = tree->extra_data.arr[extra_start];
    const uint32_t* variables = tree->extra_data.arr + extra_start + 1;

    // Detect comptime token (AstGen.zig:3462-3464).
    // Check if the first variable's first token (or the token before it)
    // is keyword_comptime.
    bool has_comptime = false;
    if (variable_count > 0) {
        uint32_t first_var = variables[0];
        AstNodeTag first_tag = tree->nodes.tags[first_var];
        uint32_t first_tok;
        if (first_tag == AST_NODE_GLOBAL_VAR_DECL
            || first_tag == AST_NODE_LOCAL_VAR_DECL
            || first_tag == AST_NODE_ALIGNED_VAR_DECL
            || first_tag == AST_NODE_SIMPLE_VAR_DECL) {
            first_tok = firstToken(tree, first_var);
        } else {
            first_tok = firstToken(tree, first_var) - 1;
        }
        if (first_tok < tree->tokens.len
            && tree->tokens.tags[first_tok] == TOKEN_KEYWORD_COMPTIME) {
            has_comptime = true;
        }
    }

    if (has_comptime && gz->is_comptime) {
        // Redundant comptime in already comptime scope (AstGen.zig:3466-3468).
        SET_ERROR(ag);
        return;
    }

    // If comptime, wrap in sub-block (AstGen.zig:3471-3477).
    GenZir gz_buf;
    GenZir* inner_gz = gz;
    if (has_comptime) {
        gz_buf = makeSubBlock(gz, scope);
        gz_buf.is_comptime = true;
        inner_gz = &gz_buf;
    }

    // Build rl_components (AstGen.zig:3479-3492).
    DestructureComponent* rl_components
        = malloc(variable_count * sizeof(DestructureComponent));
    if (!rl_components)
        exit(1);
    for (uint32_t i = 0; i < variable_count; i++) {
        uint32_t variable_node = variables[i];
        // Check for `_` identifier (AstGen.zig:3481-3487).
        if (tree->nodes.tags[variable_node] == AST_NODE_IDENTIFIER) {
            uint32_t ident_tok = tree->nodes.main_tokens[variable_node];
            uint32_t tok_start = tree->tokens.starts[ident_tok];
            if (tree->source[tok_start] == '_'
                && (tok_start + 1 >= tree->source_len
                    || !((tree->source[tok_start + 1] >= 'a'
                             && tree->source[tok_start + 1] <= 'z')
                        || (tree->source[tok_start + 1] >= 'A'
                            && tree->source[tok_start + 1] <= 'Z')
                        || tree->source[tok_start + 1] == '_'
                        || (tree->source[tok_start + 1] >= '0'
                            && tree->source[tok_start + 1] <= '9')))) {
                rl_components[i].tag = DC_DISCARD;
                rl_components[i].inst = 0;
                rl_components[i].src_node = 0;
                continue;
            }
        }
        // lvalExpr: evaluate as ref (AstGen.zig:3488-3491).
        rl_components[i].tag = DC_TYPED_PTR;
        rl_components[i].inst
            = exprRl(inner_gz, scope, RL_REF_VAL, variable_node);
        rl_components[i].src_node = variable_node;
    }

    // Build destructure result location and evaluate RHS
    // (AstGen.zig:3494-3499).
    ResultLoc ds_rl;
    memset(&ds_rl, 0, sizeof(ds_rl));
    ds_rl.tag = RL_DESTRUCTURE;
    ds_rl.src_node = node;
    ds_rl.components = rl_components;
    ds_rl.components_len = variable_count;
    (void)exprRl(inner_gz, scope, ds_rl, value_expr);

    // If comptime, finish block_comptime (AstGen.zig:3501-3505).
    if (has_comptime) {
        uint32_t comptime_block_inst
            = makeBlockInst(ag, ZIR_INST_BLOCK_COMPTIME, gz, node);
        addBreak(inner_gz, ZIR_INST_BREAK_INLINE, comptime_block_inst,
            ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
        setBlockComptimeBody(ag, inner_gz, comptime_block_inst,
            COMPTIME_REASON_COMPTIME_KEYWORD);
        gzAppendInstruction(gz, comptime_block_inst);
        gzUnstack(inner_gz);
    }
    free(rl_components);
}

// --- assignDestructureMaybeDecls (AstGen.zig:3507-3729) ---
// Handles destructure assignments that may contain const/var declarations.
// Returns new scope containing any declared variables.

static Scope* assignDestructureMaybeDecls(GenZir* gz, Scope* scope,
    uint32_t node, ScopeLocalVal* val_scopes, uint32_t* val_idx,
    ScopeLocalPtr* ptr_scopes, uint32_t* ptr_idx, uint32_t max_scopes) {
    (void)val_scopes;
    (void)val_idx;
    emitDbgNode(gz, node);
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    // Parse assign_destructure node.
    AstData nd = tree->nodes.datas[node];
    uint32_t extra_start = nd.lhs;
    uint32_t value_expr = nd.rhs;
    uint32_t variable_count = tree->extra_data.arr[extra_start];
    const uint32_t* variables = tree->extra_data.arr + extra_start + 1;

    // Detect comptime token.
    bool has_comptime = false;
    if (variable_count > 0) {
        uint32_t first_var = variables[0];
        AstNodeTag first_tag = tree->nodes.tags[first_var];
        uint32_t first_tok;
        if (first_tag == AST_NODE_GLOBAL_VAR_DECL
            || first_tag == AST_NODE_LOCAL_VAR_DECL
            || first_tag == AST_NODE_ALIGNED_VAR_DECL
            || first_tag == AST_NODE_SIMPLE_VAR_DECL) {
            first_tok = firstToken(tree, first_var);
        } else {
            first_tok = firstToken(tree, first_var) - 1;
        }
        if (first_tok < tree->tokens.len
            && tree->tokens.tags[first_tok] == TOKEN_KEYWORD_COMPTIME) {
            has_comptime = true;
        }
    }

    bool is_comptime = has_comptime || gz->is_comptime;
    bool value_is_comptime = tree->nodes.tags[value_expr] == AST_NODE_COMPTIME;

    if (has_comptime && gz->is_comptime) {
        SET_ERROR(ag); // redundant comptime
    }

    // First pass: build rl_components (AstGen.zig:3535-3620).
    DestructureComponent* rl_components
        = malloc(variable_count * sizeof(DestructureComponent));
    if (!rl_components)
        exit(1);
    bool any_lvalue_expr = false;

    for (uint32_t i = 0; i < variable_count; i++) {
        uint32_t variable_node = variables[i];
        AstNodeTag vtag = tree->nodes.tags[variable_node];

        // Check for `_` identifier (AstGen.zig:3537-3544).
        if (vtag == AST_NODE_IDENTIFIER) {
            uint32_t ident_tok = tree->nodes.main_tokens[variable_node];
            uint32_t tok_start = tree->tokens.starts[ident_tok];
            if (tree->source[tok_start] == '_'
                && (tok_start + 1 >= tree->source_len
                    || !((tree->source[tok_start + 1] >= 'a'
                             && tree->source[tok_start + 1] <= 'z')
                        || (tree->source[tok_start + 1] >= 'A'
                            && tree->source[tok_start + 1] <= 'Z')
                        || tree->source[tok_start + 1] == '_'
                        || (tree->source[tok_start + 1] >= '0'
                            && tree->source[tok_start + 1] <= '9')))) {

                rl_components[i].tag = DC_DISCARD;
                rl_components[i].inst = 0;
                rl_components[i].src_node = 0;
                continue;
            }
        }

        // var/const declarations (AstGen.zig:3545-3607).
        if (vtag == AST_NODE_GLOBAL_VAR_DECL || vtag == AST_NODE_LOCAL_VAR_DECL
            || vtag == AST_NODE_SIMPLE_VAR_DECL
            || vtag == AST_NODE_ALIGNED_VAR_DECL) {
            AstData vnd = tree->nodes.datas[variable_node];
            uint32_t mut_token = tree->nodes.main_tokens[variable_node];
            bool var_is_const
                = (tree->tokens.tags[mut_token] == TOKEN_KEYWORD_CONST);
            bool this_comptime
                = is_comptime || (var_is_const && value_is_comptime);

            uint32_t type_node = vnd.lhs;
            // AstGen.zig:3576-3607: typed vs inferred alloc.
            if (type_node != 0) {
                uint32_t type_inst = typeExpr(gz, scope, type_node);
                ZirInstTag alloc_tag;
                if (var_is_const)
                    alloc_tag = ZIR_INST_ALLOC;
                else if (this_comptime)
                    alloc_tag = ZIR_INST_ALLOC_COMPTIME_MUT;
                else
                    alloc_tag = ZIR_INST_ALLOC_MUT;
                uint32_t ptr = addUnNode(gz, alloc_tag, type_inst, node);
                rl_components[i].tag = DC_TYPED_PTR;
                rl_components[i].inst = ptr;
                rl_components[i].src_node = 0;
            } else {
                // Inferred alloc.
                ZirInstTag alloc_tag;
                if (var_is_const) {
                    alloc_tag = this_comptime
                        ? ZIR_INST_ALLOC_INFERRED_COMPTIME
                        : ZIR_INST_ALLOC_INFERRED;
                } else {
                    alloc_tag = this_comptime
                        ? ZIR_INST_ALLOC_INFERRED_COMPTIME_MUT
                        : ZIR_INST_ALLOC_INFERRED_MUT;
                }
                uint32_t ptr = addNode(gz, alloc_tag, node);
                rl_components[i].tag = DC_INFERRED_PTR;
                rl_components[i].inst = ptr;
                rl_components[i].src_node = 0;
            }
            continue;
        }
        // Lvalue expression (AstGen.zig:3609-3618).
        any_lvalue_expr = true;
        rl_components[i].tag = DC_TYPED_PTR;
        rl_components[i].inst = 0; // will be filled in second pass
        rl_components[i].src_node = variable_node;
    }

    // If comptime, wrap in sub-block (AstGen.zig:3627-3632).
    GenZir gz_buf;
    GenZir* inner_gz = gz;
    if (has_comptime) {
        gz_buf = makeSubBlock(gz, scope);
        gz_buf.is_comptime = true;
        inner_gz = &gz_buf;
    }

    // Second pass for lvalue expressions (AstGen.zig:3634-3642).
    if (any_lvalue_expr) {
        for (uint32_t i = 0; i < variable_count; i++) {
            if (rl_components[i].tag != DC_TYPED_PTR)
                continue;
            AstNodeTag vtag = tree->nodes.tags[variables[i]];
            if (vtag == AST_NODE_GLOBAL_VAR_DECL
                || vtag == AST_NODE_LOCAL_VAR_DECL
                || vtag == AST_NODE_SIMPLE_VAR_DECL
                || vtag == AST_NODE_ALIGNED_VAR_DECL)
                continue;
            rl_components[i].inst
                = exprRl(inner_gz, scope, RL_REF_VAL, variables[i]);
        }
    }

    // Evaluate RHS with destructure RL (AstGen.zig:3647-3652).
    ResultLoc ds_rl;
    memset(&ds_rl, 0, sizeof(ds_rl));
    ds_rl.tag = RL_DESTRUCTURE;
    ds_rl.src_node = node;
    ds_rl.components = rl_components;
    ds_rl.components_len = variable_count;
    (void)exprRl(inner_gz, scope, ds_rl, value_expr);

    // If comptime, finish block_comptime (AstGen.zig:3654-3660).
    if (has_comptime) {
        uint32_t comptime_block_inst
            = makeBlockInst(ag, ZIR_INST_BLOCK_COMPTIME, gz, node);
        addBreak(inner_gz, ZIR_INST_BREAK_INLINE, comptime_block_inst,
            ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
        setBlockComptimeBody(ag, inner_gz, comptime_block_inst,
            COMPTIME_REASON_COMPTIME_KEYWORD);
        gzAppendInstruction(gz, comptime_block_inst);
        gzUnstack(inner_gz);
    }

    // Third pass: create scopes for declared variables (AstGen.zig:3664-3729).
    Scope* cur_scope = scope;
    for (uint32_t i = 0; i < variable_count; i++) {
        uint32_t variable_node = variables[i];
        AstNodeTag vtag = tree->nodes.tags[variable_node];
        if (vtag != AST_NODE_LOCAL_VAR_DECL && vtag != AST_NODE_SIMPLE_VAR_DECL
            && vtag != AST_NODE_ALIGNED_VAR_DECL)
            continue;

        uint32_t mut_token = tree->nodes.main_tokens[variable_node];
        bool var_is_const
            = (tree->tokens.tags[mut_token] == TOKEN_KEYWORD_CONST);
        uint32_t raw_ptr = rl_components[i].inst;
        bool resolve_inferred = (rl_components[i].tag == DC_INFERRED_PTR);

        // Resolve inferred alloc or make ptr const (AstGen.zig:3694-3700).
        uint32_t final_ptr;
        if (resolve_inferred)
            final_ptr = addUnNode(
                gz, ZIR_INST_RESOLVE_INFERRED_ALLOC, raw_ptr, variable_node);
        else if (var_is_const)
            final_ptr = addUnNode(gz, ZIR_INST_MAKE_PTR_CONST, raw_ptr, node);
        else
            final_ptr = raw_ptr;

        // Create dbg_var_ptr (AstGen.zig:3710).
        uint32_t name_token = mut_token + 1;
        uint32_t ident_name = identAsString(ag, name_token);
        addDbgVar(gz, ZIR_INST_DBG_VAR_PTR, ident_name, final_ptr);

        // Create scope (AstGen.zig:3712-3722).
        if (*ptr_idx < max_scopes) {
            ptr_scopes[*ptr_idx] = (ScopeLocalPtr) {
                .base = { .tag = SCOPE_LOCAL_PTR },
                .parent = cur_scope,
                .name = ident_name,
                .ptr = final_ptr,
            };
            cur_scope = &ptr_scopes[*ptr_idx].base;
            (*ptr_idx)++;
        } else {
            SET_ERROR(ag);
        }
    }
    free(rl_components);
    return cur_scope;
}

// --- assignOp (AstGen.zig:3731) ---
// Handles compound assignment operators (+=, -=, *=, etc.).

static void assignOp(
    GenZir* gz, Scope* scope, uint32_t infix_node, ZirInstTag op_tag) {
    emitDbgNode(gz, infix_node);
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    AstData nd = tree->nodes.datas[infix_node];
    uint32_t lhs_node = nd.lhs;
    uint32_t rhs_node = nd.rhs;

    // Evaluate LHS as lvalue pointer (AstGen.zig:3742).
    uint32_t lhs_ptr = exprRl(gz, scope, RL_REF_VAL, lhs_node);

    // Advance cursor for add/sub/mul/div/mod_rem (AstGen.zig:3744-3747).
    uint32_t cursor_line = 0, cursor_col = 0;
    bool need_dbg = false;
    if (op_tag == ZIR_INST_ADD || op_tag == ZIR_INST_SUB
        || op_tag == ZIR_INST_MUL || op_tag == ZIR_INST_DIV
        || op_tag == ZIR_INST_MOD_REM) {
        if (!gz->is_comptime) {
            advanceSourceCursorToMainToken(ag, gz, infix_node);
        }
        cursor_line = ag->source_line - gz->decl_line;
        cursor_col = ag->source_column;
        need_dbg = true;
    }

    // Load current value (AstGen.zig:3748).
    uint32_t lhs = addUnNode(gz, ZIR_INST_LOAD, lhs_ptr, infix_node);

    // Determine RHS result type (AstGen.zig:3750-3766).
    uint32_t rhs_res_ty;
    if (op_tag == ZIR_INST_ADD || op_tag == ZIR_INST_SUB) {
        // Emit inplace_arith_result_ty extended instruction.
        uint16_t inplace_op
            = (op_tag == ZIR_INST_ADD) ? 0 : 1; // add_eq=0, sub_eq=1
        ZirInstData ext_data;
        memset(&ext_data, 0, sizeof(ext_data));
        ext_data.extended.opcode = (uint16_t)ZIR_EXT_INPLACE_ARITH_RESULT_TY;
        ext_data.extended.small = inplace_op;
        ext_data.extended.operand = lhs;
        rhs_res_ty = addInstruction(gz, ZIR_INST_EXTENDED, ext_data);
    } else {
        rhs_res_ty = addUnNode(gz, ZIR_INST_TYPEOF, lhs, infix_node);
    }

    // Evaluate RHS with type coercion (AstGen.zig:3768).
    uint32_t rhs_raw = expr(gz, scope, rhs_node);
    uint32_t rhs
        = addPlNodeBin(gz, ZIR_INST_AS_NODE, rhs_node, rhs_res_ty, rhs_raw);

    // Emit debug statement for arithmetic ops (AstGen.zig:3770-3775).
    if (need_dbg) {
        emitDbgStmt(gz, cursor_line, cursor_col);
    }

    // Emit the operation (AstGen.zig:3776-3779).
    uint32_t result = addPlNodeBin(gz, op_tag, infix_node, lhs, rhs);

    // Store result back (AstGen.zig:3780-3783).
    addPlNodeBin(gz, ZIR_INST_STORE_NODE, infix_node, lhs_ptr, result);
}

// --- assignShift (AstGen.zig:3786) ---
// Handles <<= and >>= assignment operators.

static void assignShift(
    GenZir* gz, Scope* scope, uint32_t infix_node, ZirInstTag op_tag) {
    emitDbgNode(gz, infix_node);
    const AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    AstData nd = tree->nodes.datas[infix_node];
    uint32_t lhs_node = nd.lhs;
    uint32_t rhs_node = nd.rhs;

    // Evaluate LHS as lvalue pointer (AstGen.zig:3797).
    uint32_t lhs_ptr = exprRl(gz, scope, RL_REF_VAL, lhs_node);
    // Load current value (AstGen.zig:3798).
    uint32_t lhs = addUnNode(gz, ZIR_INST_LOAD, lhs_ptr, infix_node);
    // RHS type is typeof_log2_int_type of LHS (AstGen.zig:3799).
    uint32_t rhs_type
        = addUnNode(gz, ZIR_INST_TYPEOF_LOG2_INT_TYPE, lhs, infix_node);
    ResultLoc rhs_rl = {
        .tag = RL_TY, .data = rhs_type, .src_node = 0, .ctx = RI_CTX_NONE
    };
    uint32_t rhs = exprRl(gz, scope, rhs_rl, rhs_node);

    // Emit the shift operation (AstGen.zig:3802-3805).
    uint32_t result = addPlNodeBin(gz, op_tag, infix_node, lhs, rhs);
    // Store result back (AstGen.zig:3806-3809).
    addPlNodeBin(gz, ZIR_INST_STORE_NODE, infix_node, lhs_ptr, result);
}

// --- assignShiftSat (AstGen.zig:3812) ---
// Handles <<|= saturating shift-left assignment.

static void assignShiftSat(GenZir* gz, Scope* scope, uint32_t infix_node) {
    emitDbgNode(gz, infix_node);
    const AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;

    AstData nd = tree->nodes.datas[infix_node];
    uint32_t lhs_node = nd.lhs;
    uint32_t rhs_node = nd.rhs;

    // Evaluate LHS as lvalue pointer (AstGen.zig:3818).
    uint32_t lhs_ptr = exprRl(gz, scope, RL_REF_VAL, lhs_node);
    // Load current value (AstGen.zig:3819).
    uint32_t lhs = addUnNode(gz, ZIR_INST_LOAD, lhs_ptr, infix_node);
    // Saturating shift-left allows any integer type for both LHS and RHS
    // (AstGen.zig:3820-3821).
    uint32_t rhs = expr(gz, scope, rhs_node);

    // Emit shl_sat (AstGen.zig:3823-3825).
    uint32_t result = addPlNodeBin(gz, ZIR_INST_SHL_SAT, infix_node, lhs, rhs);
    // Store result back (AstGen.zig:3827-3830).
    addPlNodeBin(gz, ZIR_INST_STORE_NODE, infix_node, lhs_ptr, result);
}

// --- builtinEvalToError (BuiltinFn.zig) ---
// Returns per-builtin eval_to_error. Default is .never; only a few are
// .maybe or .always. Mirrors BuiltinFn.list lookup in AstGen.zig:10539.
static int builtinEvalToError(const Ast* tree, uint32_t node) {
    uint32_t main_tok = tree->nodes.main_tokens[node];
    uint32_t tok_start = tree->tokens.starts[main_tok];
    const char* source = tree->source;
    uint32_t name_start = tok_start + 1; // skip '@'
    uint32_t name_end = name_start;
    while (name_end < tree->source_len
        && ((source[name_end] >= 'a' && source[name_end] <= 'z')
            || (source[name_end] >= 'A' && source[name_end] <= 'Z')
            || source[name_end] == '_')) {
        name_end++;
    }
    uint32_t name_len = name_end - name_start;
    const char* name = source + name_start;
    // clang-format off
    // .always:
    if (name_len == 12 && memcmp(name, "errorFromInt", 12) == 0)
        return 1; // EVAL_TO_ERROR_ALWAYS
    // .maybe:
    if (name_len == 2 && memcmp(name, "as", 2) == 0) return 2;
    if (name_len == 4 && memcmp(name, "call", 4) == 0) return 2;
    if (name_len == 5 && memcmp(name, "field", 5) == 0) return 2;
    if (name_len == 9 && memcmp(name, "errorCast", 9) == 0) return 2;
    // clang-format on
    // Default: .never
    return 0;
}

// --- nodeMayEvalToError (AstGen.zig:10340) ---
// Three-way result: 0=never, 1=always, 2=maybe.
#define EVAL_TO_ERROR_NEVER 0
#define EVAL_TO_ERROR_ALWAYS 1
#define EVAL_TO_ERROR_MAYBE 2

static int nodeMayEvalToError(const Ast* tree, uint32_t node) {
    uint32_t n = node;
    while (true) {
        AstNodeTag tag = tree->nodes.tags[n];
        switch (tag) {
        case AST_NODE_ERROR_VALUE:
            return EVAL_TO_ERROR_ALWAYS;
        // These may evaluate to errors.
        case AST_NODE_IDENTIFIER:
        case AST_NODE_FIELD_ACCESS:
        case AST_NODE_DEREF:
        case AST_NODE_ARRAY_ACCESS:
        case AST_NODE_WHILE_SIMPLE:
        case AST_NODE_WHILE_CONT:
        case AST_NODE_WHILE:
        case AST_NODE_FOR_SIMPLE:
        case AST_NODE_FOR:
        case AST_NODE_IF_SIMPLE:
        case AST_NODE_IF:
        case AST_NODE_SWITCH:
        case AST_NODE_SWITCH_COMMA:
        case AST_NODE_CALL_ONE:
        case AST_NODE_CALL_ONE_COMMA:
        case AST_NODE_CALL:
        case AST_NODE_CALL_COMMA:
        case AST_NODE_ASM_SIMPLE:
        case AST_NODE_ASM_LEGACY:
        case AST_NODE_ASM:
        case AST_NODE_CATCH:
        case AST_NODE_ORELSE:
            return EVAL_TO_ERROR_MAYBE;
        // Forward to sub-expression.
        case AST_NODE_TRY:
        case AST_NODE_COMPTIME:
        case AST_NODE_NOSUSPEND:
            n = tree->nodes.datas[n].lhs;
            continue;
        case AST_NODE_GROUPED_EXPRESSION:
        case AST_NODE_UNWRAP_OPTIONAL:
            n = tree->nodes.datas[n].lhs;
            continue;
        // Labeled blocks may need a memory location.
        case AST_NODE_BLOCK_TWO:
        case AST_NODE_BLOCK_TWO_SEMICOLON:
        case AST_NODE_BLOCK:
        case AST_NODE_BLOCK_SEMICOLON: {
            uint32_t lbrace = tree->nodes.main_tokens[n];
            if (lbrace > 0 && tree->tokens.tags[lbrace - 1] == TOKEN_COLON)
                return EVAL_TO_ERROR_MAYBE;
            return EVAL_TO_ERROR_NEVER;
        }
        // Builtins: look up per-builtin eval_to_error
        // (AstGen.zig:10530-10541).
        case AST_NODE_BUILTIN_CALL:
        case AST_NODE_BUILTIN_CALL_COMMA:
        case AST_NODE_BUILTIN_CALL_TWO:
        case AST_NODE_BUILTIN_CALL_TWO_COMMA:
            return builtinEvalToError(tree, n);
        // Everything else: .never
        default:
            return EVAL_TO_ERROR_NEVER;
        }
    }
}

// --- nodeMayAppendToErrorTrace (AstGen.zig:10315) ---
// Returns true if the expression may append to the error return trace.
static bool nodeMayAppendToErrorTrace(const Ast* tree, uint32_t node) {
    uint32_t n = node;
    while (true) {
        AstNodeTag tag = tree->nodes.tags[n];
        switch (tag) {
        // These don't call runtime functions.
        case AST_NODE_ERROR_VALUE:
        case AST_NODE_IDENTIFIER:
        case AST_NODE_COMPTIME:
            return false;
        // Forward to sub-expression.
        case AST_NODE_TRY:
        case AST_NODE_NOSUSPEND:
            n = tree->nodes.datas[n].lhs;
            continue;
        case AST_NODE_GROUPED_EXPRESSION:
        case AST_NODE_UNWRAP_OPTIONAL:
            n = tree->nodes.datas[n].lhs;
            continue;
        // Anything else: check if it may eval to error.
        default:
            return nodeMayEvalToError(tree, n) != EVAL_TO_ERROR_NEVER;
        }
    }
}

// --- addSaveErrRetIndex (AstGen.zig:12556) ---
// Emits SAVE_ERR_RET_INDEX instruction.
// operand is the init inst ref (or ZIR_REF_NONE for .always).
static void addSaveErrRetIndex(GenZir* gz, uint32_t operand) {
    ZirInstData data;
    data.save_err_ret_index.operand = operand;
    data.save_err_ret_index._pad = 0;
    addInstruction(gz, ZIR_INST_SAVE_ERR_RET_INDEX, data);
}

// --- addRestoreErrRetIndexBlock (AstGen.zig:12607-12614) ---
// Emits extended RESTORE_ERR_RET_INDEX with block target (if_non_error
// condition). Payload: src_node, block_ref, operand.
static void addRestoreErrRetIndexBlock(
    GenZir* gz, uint32_t block_inst, uint32_t operand, uint32_t node) {
    AstGenCtx* ag = gz->astgen;
    ensureExtraCapacity(ag, 3);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++]
        = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);
    ag->extra[ag->extra_len++] = block_inst + ZIR_REF_START_INDEX;
    ag->extra[ag->extra_len++] = operand;

    ZirInstData ext_data;
    ext_data.extended.opcode = (uint16_t)ZIR_EXT_RESTORE_ERR_RET_INDEX;
    ext_data.extended.small = 0;
    ext_data.extended.operand = payload_index;
    addInstruction(gz, ZIR_INST_EXTENDED, ext_data);
}

// --- restoreErrRetIndex (AstGen.zig:2121-2148) ---
// Emits restore_err_ret_index for block target based on nodeMayEvalToError.
static void restoreErrRetIndex(GenZir* gz, uint32_t block_inst, ResultLoc rl,
    uint32_t node, uint32_t result) {
    const Ast* tree = gz->astgen->tree;
    int eval = nodeMayEvalToError(tree, node);
    if (eval == EVAL_TO_ERROR_ALWAYS)
        return; // never restore/pop
    uint32_t op;
    if (eval == EVAL_TO_ERROR_NEVER) {
        op = ZIR_REF_NONE; // always restore/pop
    } else {
        // EVAL_TO_ERROR_MAYBE
        // Simplified: without ri.ctx, treat non-ptr RL as result
        // (AstGen.zig:2131-2144).
        if (rl.tag == RL_PTR) {
            op = addUnNode(gz, ZIR_INST_LOAD, rl.data, node);
        } else if (rl.tag == RL_INFERRED_PTR) {
            op = ZIR_REF_NONE;
        } else {
            op = result;
        }
    }
    addRestoreErrRetIndexBlock(gz, block_inst, op, node);
}

// --- varDecl (AstGen.zig:3189) ---
// Handles local const/var declarations. Returns new scope with the variable.
// scope_out: set to new scope if variable is added; unchanged otherwise.

static void varDecl(GenZir* gz, Scope* scope, uint32_t node,
    ScopeLocalVal* val_out, ScopeLocalPtr* ptr_out, Scope** scope_out) {
    AstGenCtx* ag = gz->astgen;
    emitDbgNode(gz, node); // AstGen.zig:3196
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];
    AstNodeTag tag = tree->nodes.tags[node];

    uint32_t mut_token = tree->nodes.main_tokens[node];
    uint32_t name_token = mut_token + 1;
    bool is_const = (tree->source[tree->tokens.starts[mut_token]] == 'c');

    uint32_t ident_name = identAsString(ag, name_token);

    // Extract comptime_token by scanning backwards from mut_token
    // (Ast.zig:2012-2023, fullVarDeclComponents).
    bool has_comptime_token = false;
    if (mut_token > 0
        && tree->tokens.tags[mut_token - 1] == TOKEN_KEYWORD_COMPTIME) {
        has_comptime_token = true;
    }

    // Extract type_node and init_node based on variant.
    uint32_t type_node = 0;
    uint32_t align_node = 0;
    uint32_t init_node = 0;

    if (tag == AST_NODE_SIMPLE_VAR_DECL) {
        // lhs = type (optional), rhs = init (optional).
        type_node = nd.lhs;
        init_node = nd.rhs;
    } else if (tag == AST_NODE_LOCAL_VAR_DECL) {
        // lhs = extra_data index, rhs = init.
        // extra: {type_node, align_node, addrspace_node, section_node}
        uint32_t extra_idx = nd.lhs;
        type_node = tree->extra_data.arr[extra_idx]; // type_node
        align_node = tree->extra_data.arr[extra_idx + 1]; // align_node
        init_node = nd.rhs;
    } else if (tag == AST_NODE_ALIGNED_VAR_DECL) {
        // lhs = align expr, rhs = init.
        // No type node in this variant.
        align_node = nd.lhs;
        init_node = nd.rhs;
    } else {
        // global_var_decl or unknown — bail.
        SET_ERROR(ag);
        return;
    }

    if (init_node == 0) {
        // Variables must be initialized (AstGen.zig:3228).
        SET_ERROR(ag);
        return;
    }

    // Evaluate alignment expression (AstGen.zig:3227-3230).
    uint32_t align_inst = ZIR_REF_NONE;
    if (align_node != 0) {
        ResultLoc align_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_U29_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE,
            .components = NULL,
            .components_len = 0 };
        align_inst = exprRl(gz, scope, align_rl, align_node);
    }

    if (is_const) {
        // --- CONST path (AstGen.zig:3232-3340) ---

        // `comptime const` is a non-fatal error; treat it like the init was
        // marked `comptime` (AstGen.zig:3234-3239).
        uint32_t force_comptime
            = has_comptime_token ? COMPTIME_REASON_COMPTIME_KEYWORD : 0;

        if (!nodesNeedRlContains(ag, node)) {
            // Rvalue path (AstGen.zig:3246-3271).
            // Evaluate type annotation and build result_info
            // (AstGen.zig:3247-3250).
            ResultLoc result_info;
            if (type_node != 0) {
                uint32_t type_ref = typeExpr(gz, scope, type_node);
                result_info = (ResultLoc) { .tag = RL_TY,
                    .data = type_ref,
                    .src_node = 0,
                    .ctx = RI_CTX_CONST_INIT };
            } else {
                result_info = (ResultLoc) { .tag = RL_NONE,
                    .data = 0,
                    .src_node = 0,
                    .ctx = RI_CTX_CONST_INIT };
            }

            // Evaluate init expression (AstGen.zig:3251-3252).
            uint32_t init_ref = reachableExprComptime(
                gz, scope, result_info, init_node, node, force_comptime);

            if (ag->has_compile_errors)
                return;

            // validate_const (AstGen.zig:3266).
            addUnNode(gz, ZIR_INST_VALIDATE_CONST, init_ref, init_node);

            // dbg_var_val (AstGen.zig:3269).
            addDbgVar(gz, ZIR_INST_DBG_VAR_VAL, ident_name, init_ref);

            // save_err_ret_index (AstGen.zig:3259-3260).
            if (nodeMayAppendToErrorTrace(tree, init_node))
                addSaveErrRetIndex(gz, init_ref);

            // Create ScopeLocalVal (AstGen.zig:3276-3284).
            val_out->base.tag = SCOPE_LOCAL_VAL;
            val_out->parent = *scope_out;
            val_out->gen_zir = gz;
            val_out->inst = init_ref;
            val_out->token_src = name_token;
            val_out->name = ident_name;
            val_out->is_used_or_discarded = NULL;
            *scope_out = &val_out->base;
        } else {
            // Alloc path (AstGen.zig:3277-3340).
            // The init expression needs a result pointer (nodes_need_rl).
            bool is_comptime_init = gz->is_comptime
                || tree->nodes.tags[init_node] == AST_NODE_COMPTIME;

            uint32_t var_ptr;
            bool resolve_inferred;

            if (type_node != 0) {
                // Typed const: alloc (AstGen.zig:3280).
                uint32_t type_ref = typeExpr(gz, scope, type_node);
                var_ptr = addUnNode(gz, ZIR_INST_ALLOC, type_ref, node);
                resolve_inferred = false;
            } else {
                // Inferred type: alloc_inferred (AstGen.zig:3291-3296).
                ZirInstTag alloc_tag = is_comptime_init
                    ? ZIR_INST_ALLOC_INFERRED_COMPTIME
                    : ZIR_INST_ALLOC_INFERRED;
                ZirInstData adata;
                adata.node = (int32_t)node - (int32_t)gz->decl_node_index;
                var_ptr = addInstruction(gz, alloc_tag, adata);
                resolve_inferred = true;
            }

            // Evaluate init with RL pointing to alloc (AstGen.zig:3313-3316).
            ResultLoc init_rl;
            init_rl.components = NULL;
            init_rl.components_len = 0;
            if (type_node != 0) {
                init_rl.tag = RL_PTR;
                init_rl.data = var_ptr;
                init_rl.src_node = 0; // upstream: .none (PtrResultLoc.src_node
                                      // defaults to null)
            } else {
                init_rl.tag = RL_INFERRED_PTR;
                init_rl.data = var_ptr;
                init_rl.src_node = 0;
            }
            init_rl.ctx = RI_CTX_CONST_INIT;
            uint32_t init_ref = reachableExprComptime(
                gz, scope, init_rl, init_node, node, force_comptime);

            if (ag->has_compile_errors)
                return;

            // save_err_ret_index (AstGen.zig:3320-3321).
            if (nodeMayAppendToErrorTrace(tree, init_node))
                addSaveErrRetIndex(gz, init_ref);

            // resolve_inferred_alloc or make_ptr_const (AstGen.zig:3323-3326).
            uint32_t const_ptr;
            if (resolve_inferred)
                const_ptr = addUnNode(
                    gz, ZIR_INST_RESOLVE_INFERRED_ALLOC, var_ptr, node);
            else
                const_ptr
                    = addUnNode(gz, ZIR_INST_MAKE_PTR_CONST, var_ptr, node);

            // dbg_var_ptr (AstGen.zig:3328).
            addDbgVar(gz, ZIR_INST_DBG_VAR_PTR, ident_name, const_ptr);

            // Create ScopeLocalPtr (AstGen.zig:3330-3340).
            ptr_out->base.tag = SCOPE_LOCAL_PTR;
            ptr_out->parent = *scope_out;
            ptr_out->gen_zir = gz;
            ptr_out->ptr = const_ptr;
            ptr_out->token_src = name_token;
            ptr_out->name = ident_name;
            ptr_out->maybe_comptime = true;
            *scope_out = &ptr_out->base;
        }
    } else {
        // --- VAR path (AstGen.zig:3342-3416) ---

        // comptime_token handling (AstGen.zig:3343-3345).
        bool is_comptime = has_comptime_token || gz->is_comptime;

        uint32_t alloc_ref;
        bool resolve_inferred = false;

        if (type_node != 0) {
            // Typed var: alloc_mut (AstGen.zig:3346-3365).
            uint32_t type_ref = typeExpr(gz, scope, type_node);
            if (align_inst == ZIR_REF_NONE) {
                ZirInstTag alloc_tag = is_comptime
                    ? ZIR_INST_ALLOC_COMPTIME_MUT
                    : ZIR_INST_ALLOC_MUT;
                alloc_ref = addUnNode(gz, alloc_tag, type_ref, node);
            } else {
                // addAllocExtended (AstGen.zig:12781-12830).
                ensureExtraCapacity(ag, 3); // src_node + type + align
                uint32_t payload_index = ag->extra_len;
                int32_t src_off = (int32_t)node - (int32_t)gz->decl_node_index;
                memcpy(&ag->extra[ag->extra_len], &src_off, sizeof(uint32_t));
                ag->extra_len++;
                ag->extra[ag->extra_len++] = type_ref;
                ag->extra[ag->extra_len++] = align_inst;
                // small: has_type=1, has_align=1, is_const=0, is_comptime
                uint16_t small = (uint16_t)(1u | (1u << 1)
                    | ((is_comptime ? 1u : 0u) << 3));
                ZirInstData edata;
                edata.extended.opcode = (uint16_t)ZIR_EXT_ALLOC;
                edata.extended.small = small;
                edata.extended.operand = payload_index;
                alloc_ref = addInstruction(gz, ZIR_INST_EXTENDED, edata);
            }
        } else {
            // Inferred type var: alloc_inferred_mut
            // (AstGen.zig:3366-3385).
            if (align_inst == ZIR_REF_NONE) {
                ZirInstTag alloc_tag = is_comptime
                    ? ZIR_INST_ALLOC_INFERRED_COMPTIME_MUT
                    : ZIR_INST_ALLOC_INFERRED_MUT;
                ZirInstData adata;
                adata.node = (int32_t)node - (int32_t)gz->decl_node_index;
                alloc_ref = addInstruction(gz, alloc_tag, adata);
            } else {
                // addAllocExtended without type (AstGen.zig:12781-12830).
                ensureExtraCapacity(ag, 2); // src_node + align
                uint32_t payload_index = ag->extra_len;
                int32_t src_off = (int32_t)node - (int32_t)gz->decl_node_index;
                memcpy(&ag->extra[ag->extra_len], &src_off, sizeof(uint32_t));
                ag->extra_len++;
                ag->extra[ag->extra_len++] = align_inst;
                // small: has_type=0, has_align=1, is_const=0, is_comptime
                uint16_t small
                    = (uint16_t)((1u << 1) | ((is_comptime ? 1u : 0u) << 3));
                ZirInstData edata;
                edata.extended.opcode = (uint16_t)ZIR_EXT_ALLOC;
                edata.extended.small = small;
                edata.extended.operand = payload_index;
                alloc_ref = addInstruction(gz, ZIR_INST_EXTENDED, edata);
            }
            resolve_inferred = true;
        }

        // Evaluate init with RL pointing to alloc (AstGen.zig:3395-3402).
        ResultLoc var_init_rl;
        var_init_rl.components = NULL;
        var_init_rl.components_len = 0;
        if (type_node != 0) {
            var_init_rl.tag = RL_PTR;
            var_init_rl.data = alloc_ref;
            var_init_rl.src_node = 0; // upstream: .none (PtrResultLoc.src_node
                                      // defaults to null)
        } else {
            var_init_rl.tag = RL_INFERRED_PTR;
            var_init_rl.data = alloc_ref;
            var_init_rl.src_node = 0;
        }
        var_init_rl.ctx = RI_CTX_NONE;
        uint32_t comptime_reason
            = has_comptime_token ? COMPTIME_REASON_COMPTIME_KEYWORD : 0;
        uint32_t init_ref = reachableExprComptime(
            gz, scope, var_init_rl, init_node, node, comptime_reason);
        (void)init_ref;

        if (ag->has_compile_errors)
            return;

        // resolve_inferred_alloc if type was inferred
        // (AstGen.zig:3407-3408).
        uint32_t final_ptr = alloc_ref;
        if (resolve_inferred)
            final_ptr = addUnNode(
                gz, ZIR_INST_RESOLVE_INFERRED_ALLOC, alloc_ref, node);

        // dbg_var_ptr (AstGen.zig:3411).
        addDbgVar(gz, ZIR_INST_DBG_VAR_PTR, ident_name, final_ptr);

        // Create ScopeLocalPtr (AstGen.zig:3413-3422).
        ptr_out->base.tag = SCOPE_LOCAL_PTR;
        ptr_out->parent = *scope_out;
        ptr_out->gen_zir = gz;
        ptr_out->ptr = final_ptr;
        ptr_out->token_src = name_token;
        ptr_out->name = ident_name;
        ptr_out->maybe_comptime = is_comptime;
        *scope_out = &ptr_out->base;
    }
}

// --- addEnsureResult (AstGen.zig:2649) ---
// After evaluating an expression as a statement, optionally emits
// ensure_result_used. For call/field_call, sets flag in extra data instead.
// Returns true if the result is noreturn (AstGen.zig:2909).
static bool addEnsureResult(
    GenZir* gz, uint32_t maybe_unused_result, uint32_t statement) {
    AstGenCtx* ag = gz->astgen;
    bool elide_check;
    bool is_noreturn = false;
    if (maybe_unused_result >= ZIR_REF_START_INDEX) {
        uint32_t inst = maybe_unused_result - ZIR_REF_START_INDEX;
        ZirInstTag tag = ag->inst_tags[inst];
        switch (tag) {
        // For call/field_call: set ensure_result_used flag
        // (bit 3 of flags at offset 0). Flags *must* be at offset 0
        // (AstGen.zig:2658-2665, Zir.zig:3022).
        case ZIR_INST_CALL:
        case ZIR_INST_FIELD_CALL: {
            uint32_t pi = ag->inst_datas[inst].pl_node.payload_index;
            ag->extra[pi] |= (1u << 3); // ensure_result_used
            elide_check = true;
            break;
        }
        // For builtin_call: ensure_result_used is at bit 1, not bit 3.
        case ZIR_INST_BUILTIN_CALL: {
            uint32_t pi = ag->inst_datas[inst].pl_node.payload_index;
            ag->extra[pi] |= (1u << 1); // ensure_result_used
            elide_check = true;
            break;
        }
        // Always noreturn → elide (AstGen.zig:2909).
        case ZIR_INST_BREAK:
        case ZIR_INST_BREAK_INLINE:
        case ZIR_INST_CONDBR:
        case ZIR_INST_CONDBR_INLINE:
        case ZIR_INST_RET_NODE:
        case ZIR_INST_RET_LOAD:
        case ZIR_INST_RET_IMPLICIT:
        case ZIR_INST_RET_ERR_VALUE:
        case ZIR_INST_UNREACHABLE:
        case ZIR_INST_REPEAT:
        case ZIR_INST_REPEAT_INLINE:
        case ZIR_INST_PANIC:
        case ZIR_INST_TRAP:
        case ZIR_INST_CHECK_COMPTIME_CONTROL_FLOW:
        case ZIR_INST_SWITCH_CONTINUE:
        case ZIR_INST_COMPILE_ERROR:
            is_noreturn = true;
            elide_check = true;
            break;
        // Always void → elide.
        case ZIR_INST_DBG_STMT:
        case ZIR_INST_DBG_VAR_PTR:
        case ZIR_INST_DBG_VAR_VAL:
        case ZIR_INST_ENSURE_RESULT_USED:
        case ZIR_INST_ENSURE_RESULT_NON_ERROR:
        case ZIR_INST_ENSURE_ERR_UNION_PAYLOAD_VOID:
        case ZIR_INST_EXPORT:
        case ZIR_INST_SET_EVAL_BRANCH_QUOTA:
        case ZIR_INST_ATOMIC_STORE:
        case ZIR_INST_STORE_NODE:
        case ZIR_INST_STORE_TO_INFERRED_PTR:
        case ZIR_INST_RESOLVE_INFERRED_ALLOC:
        case ZIR_INST_SET_RUNTIME_SAFETY:
        case ZIR_INST_MEMCPY:
        case ZIR_INST_MEMSET:
        case ZIR_INST_MEMMOVE:
        case ZIR_INST_VALIDATE_DEREF:
        case ZIR_INST_VALIDATE_DESTRUCTURE:
        case ZIR_INST_SAVE_ERR_RET_INDEX:
        case ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL:
        case ZIR_INST_RESTORE_ERR_RET_INDEX_FN_ENTRY:
        case ZIR_INST_VALIDATE_STRUCT_INIT_TY:
        case ZIR_INST_VALIDATE_STRUCT_INIT_RESULT_TY:
        case ZIR_INST_VALIDATE_PTR_STRUCT_INIT:
        case ZIR_INST_VALIDATE_ARRAY_INIT_TY:
        case ZIR_INST_VALIDATE_ARRAY_INIT_RESULT_TY:
        case ZIR_INST_VALIDATE_PTR_ARRAY_INIT:
        case ZIR_INST_VALIDATE_REF_TY:
        case ZIR_INST_VALIDATE_CONST:
            elide_check = true;
            break;
        // Extended: check opcode.
        case ZIR_INST_EXTENDED: {
            uint32_t opcode = ag->inst_datas[inst].extended.opcode;
            elide_check = (opcode == ZIR_EXT_BREAKPOINT
                || opcode == ZIR_EXT_BRANCH_HINT
                || opcode == ZIR_EXT_SET_FLOAT_MODE
                || opcode == ZIR_EXT_DISABLE_INSTRUMENTATION
                || opcode == ZIR_EXT_DISABLE_INTRINSICS);
            break;
        }
        // Everything else: might produce non-void result → emit check.
        default:
            elide_check = false;
            break;
        }
    } else {
        // Named ref constant.
        is_noreturn = (maybe_unused_result == ZIR_REF_UNREACHABLE_VALUE);
        elide_check
            = (is_noreturn || maybe_unused_result == ZIR_REF_VOID_VALUE);
    }
    if (!elide_check) {
        addUnNode(
            gz, ZIR_INST_ENSURE_RESULT_USED, maybe_unused_result, statement);
    }
    return is_noreturn;
}

// --- countDefers (AstGen.zig:2966) ---
// Walk scope chain and count defer types.

static DeferCounts countDefers(const Scope* outer_scope, Scope* inner_scope) {
    DeferCounts c = { false, false, false, false };
    Scope* s = inner_scope;
    while (s != outer_scope) {
        switch (s->tag) {
        case SCOPE_GEN_ZIR:
            s = ((GenZir*)s)->parent;
            break;
        case SCOPE_LOCAL_VAL:
            s = ((ScopeLocalVal*)s)->parent;
            break;
        case SCOPE_LOCAL_PTR:
            s = ((ScopeLocalPtr*)s)->parent;
            break;
        case SCOPE_DEFER_NORMAL: {
            ScopeDefer* d = (ScopeDefer*)s;
            s = d->parent;
            c.have_normal = true;
            break;
        }
        case SCOPE_DEFER_ERROR: {
            ScopeDefer* d = (ScopeDefer*)s;
            s = d->parent;
            c.have_err = true;
            // need_err_code if remapped_err_code exists (we don't
            // implement err capture yet, so always false).
            break;
        }
        default:
            return c;
        }
    }
    c.have_any = c.have_normal || c.have_err;
    return c;
}

// --- genDefers (AstGen.zig:3014) ---
// Walk scope chain from inner to outer, emitting .defer instructions.
// which: DEFER_NORMAL_ONLY or DEFER_BOTH_SANS_ERR.

static void genDefers(
    GenZir* gz, const Scope* outer_scope, Scope* inner_scope, int which) {
    Scope* s = inner_scope;
    while (s != outer_scope) {
        switch (s->tag) {
        case SCOPE_GEN_ZIR: {
            GenZir* g = (GenZir*)s;
            s = g->parent;
            break;
        }
        case SCOPE_LOCAL_VAL: {
            ScopeLocalVal* lv = (ScopeLocalVal*)s;
            s = lv->parent;
            break;
        }
        case SCOPE_LOCAL_PTR: {
            ScopeLocalPtr* lp = (ScopeLocalPtr*)s;
            s = lp->parent;
            break;
        }
        case SCOPE_DEFER_NORMAL: {
            ScopeDefer* d = (ScopeDefer*)s;
            s = d->parent;
            // Emit ZIR_INST_DEFER (AstGen.zig:3031).
            ZirInstData data;
            data.defer_data.index = d->index;
            data.defer_data.len = d->len;
            addInstruction(gz, ZIR_INST_DEFER, data);
            break;
        }
        case SCOPE_DEFER_ERROR: {
            ScopeDefer* d = (ScopeDefer*)s;
            s = d->parent;
            if (which == DEFER_BOTH_SANS_ERR) {
                // Emit regular DEFER for error defers too (AstGen.zig:3038).
                ZirInstData data;
                data.defer_data.index = d->index;
                data.defer_data.len = d->len;
                addInstruction(gz, ZIR_INST_DEFER, data);
            }
            // DEFER_NORMAL_ONLY: skip error defers (AstGen.zig:3063).
            break;
        }
        case SCOPE_LABEL: {
            // Labels store parent in the GenZir they're attached to.
            // Just skip by going to the parent scope stored in parent.
            // Actually labels don't have a separate parent pointer in our
            // representation; they're part of GenZir. This case shouldn't
            // appear when walking from blockExprStmts scope.
            return;
        }
        case SCOPE_NAMESPACE:
        case SCOPE_TOP:
        default:
            return;
        }
    }
}

// --- blockExprStmts (AstGen.zig:2538) ---
// Processes block statements sequentially, threading scope.

static void blockExprStmts(GenZir* gz, Scope* scope,
    const uint32_t* statements, uint32_t stmt_count) {
    AstGenCtx* ag = gz->astgen;
    // Stack-allocated scope storage for local variables and defers.
    // Max 128 local variable declarations and 128 defers per block.
    ScopeLocalVal val_scopes[128];
    ScopeLocalPtr ptr_scopes[128];
    ScopeDefer defer_scopes[128];
    uint32_t val_idx = 0;
    uint32_t ptr_idx = 0;
    uint32_t defer_idx = 0;
    Scope* cur_scope = scope;
    bool noreturn_stmt = false;

    for (uint32_t i = 0; i < stmt_count; i++) {
        if (ag->has_compile_errors)
            return;
        uint32_t stmt = statements[i];
        // Unwrap grouped_expression (parentheses) before dispatching
        // (AstGen.zig:2569-2630).
        uint32_t inner_node = stmt;
        for (;;) {
            AstNodeTag tag = ag->tree->nodes.tags[inner_node];
            switch (tag) {
            case AST_NODE_ASSIGN:
                assignStmt(gz, cur_scope, inner_node);
                break;
            // assign_destructure (AstGen.zig:2578).
            case AST_NODE_ASSIGN_DESTRUCTURE:
                cur_scope
                    = assignDestructureMaybeDecls(gz, cur_scope, inner_node,
                        val_scopes, &val_idx, ptr_scopes, &ptr_idx, 128);
                break;
            // Shift assignment operators (AstGen.zig:2585-2586).
            case AST_NODE_ASSIGN_SHL:
                assignShift(gz, cur_scope, inner_node, ZIR_INST_SHL);
                break;
            case AST_NODE_ASSIGN_SHR:
                assignShift(gz, cur_scope, inner_node, ZIR_INST_SHR);
                break;
            // Saturating shift-left assignment (AstGen.zig:680-682 via expr).
            case AST_NODE_ASSIGN_SHL_SAT:
                assignShiftSat(gz, cur_scope, inner_node);
                break;
            // Compound assignment operators (AstGen.zig:2588-2607).
            case AST_NODE_ASSIGN_ADD:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_ADD);
                break;
            case AST_NODE_ASSIGN_SUB:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_SUB);
                break;
            case AST_NODE_ASSIGN_MUL:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_MUL);
                break;
            case AST_NODE_ASSIGN_DIV:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_DIV);
                break;
            case AST_NODE_ASSIGN_MOD:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_MOD_REM);
                break;
            case AST_NODE_ASSIGN_BIT_AND:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_BIT_AND);
                break;
            case AST_NODE_ASSIGN_BIT_OR:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_BIT_OR);
                break;
            case AST_NODE_ASSIGN_BIT_XOR:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_XOR);
                break;
            case AST_NODE_ASSIGN_ADD_WRAP:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_ADDWRAP);
                break;
            case AST_NODE_ASSIGN_SUB_WRAP:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_SUBWRAP);
                break;
            case AST_NODE_ASSIGN_MUL_WRAP:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_MULWRAP);
                break;
            case AST_NODE_ASSIGN_ADD_SAT:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_ADD_SAT);
                break;
            case AST_NODE_ASSIGN_SUB_SAT:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_SUB_SAT);
                break;
            case AST_NODE_ASSIGN_MUL_SAT:
                assignOp(gz, cur_scope, inner_node, ZIR_INST_MUL_SAT);
                break;
            case AST_NODE_SIMPLE_VAR_DECL:
            case AST_NODE_LOCAL_VAR_DECL:
            case AST_NODE_ALIGNED_VAR_DECL:
                if (val_idx < 128 && ptr_idx < 128) {
                    varDecl(gz, cur_scope, stmt, &val_scopes[val_idx],
                        &ptr_scopes[ptr_idx], &cur_scope);
                    // Check which one was used: if scope now points to
                    // val_scopes[val_idx], advance val_idx; same for ptr.
                    if (cur_scope == &val_scopes[val_idx].base)
                        val_idx++;
                    else if (cur_scope == &ptr_scopes[ptr_idx].base)
                        ptr_idx++;
                } else {
                    SET_ERROR(ag);
                }
                break;
            // defer/errdefer (AstGen.zig:2580-2581).
            case AST_NODE_DEFER:
            case AST_NODE_ERRDEFER: {
                if (defer_idx >= 128) {
                    SET_ERROR(ag);
                    break;
                }
                ScopeTag scope_tag = (tag == AST_NODE_DEFER)
                    ? SCOPE_DEFER_NORMAL
                    : SCOPE_DEFER_ERROR;
                // Create sub-block for defer body (AstGen.zig:3123-3126).
                GenZir defer_gen = makeSubBlock(gz, cur_scope);
                defer_gen.any_defer_node = stmt; // AstGen.zig:3125

                // Evaluate deferred expression (AstGen.zig:3165).
                // DEFER: lhs is the deferred expression, rhs = 0.
                // ERRDEFER: lhs is optional error capture token, rhs is expr.
                AstData dnd = ag->tree->nodes.datas[stmt];
                uint32_t expr_node;
                if (tag == AST_NODE_DEFER) {
                    expr_node = dnd.lhs;
                } else {
                    expr_node = dnd.rhs;
                }
                // unusedResultExpr pattern (AstGen.zig:3165, 2641-2646).
                emitDbgNode(&defer_gen, expr_node);
                uint32_t defer_result
                    = expr(&defer_gen, &defer_gen.base, expr_node);
                addEnsureResult(&defer_gen, defer_result, expr_node);

                // Add break_inline at end (AstGen.zig:3167).
                addBreak(&defer_gen, ZIR_INST_BREAK_INLINE, 0,
                    ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);

                // Write body to extra (AstGen.zig:3173-3175).
                uint32_t raw_body_len = gzInstructionsLen(&defer_gen);
                const uint32_t* body = gzInstructionsSlice(&defer_gen);
                uint32_t extra_index = ag->extra_len;
                uint32_t fixup_len
                    = countBodyLenAfterFixups(ag, body, raw_body_len);
                ensureExtraCapacity(ag, fixup_len);
                for (uint32_t b = 0; b < raw_body_len; b++)
                    appendPossiblyRefdBodyInst(ag, body[b]);
                gzUnstack(&defer_gen);

                // Create scope (AstGen.zig:3179-3185).
                defer_scopes[defer_idx] = (ScopeDefer) {
                    .base = { .tag = scope_tag },
                    .parent = cur_scope,
                    .index = extra_index,
                    .len = fixup_len,
                };
                cur_scope = &defer_scopes[defer_idx].base;
                defer_idx++;
                break;
            }
            // Grouped expression: unwrap parentheses (AstGen.zig:2600-2602).
            case AST_NODE_GROUPED_EXPRESSION:
                inner_node = ag->tree->nodes.datas[inner_node].lhs;
                continue;
            // while/for as statements (AstGen.zig:2605-2610).
            // These do NOT get emitDbgNode; they emit their own dbg_stmt.
            case AST_NODE_WHILE_SIMPLE:
            case AST_NODE_WHILE_CONT:
            case AST_NODE_WHILE:
                (void)whileExpr(gz, cur_scope, RL_NONE_VAL, inner_node, true);
                break;
            case AST_NODE_FOR_SIMPLE:
            case AST_NODE_FOR:
                (void)forExpr(gz, cur_scope, RL_NONE_VAL, inner_node, true);
                break;
            default: {
                // Expression statement (AstGen.zig:2627 unusedResultExpr).
                emitDbgNode(gz, inner_node);
                uint32_t result = expr(gz, cur_scope, inner_node);
                noreturn_stmt = addEnsureResult(gz, result, inner_node);
                break;
            }
            }
            break; // Break out of the for(;;) unwrapping loop.
        }
    }
    // Emit normal defers at block exit (AstGen.zig:2633-2634).
    if (!noreturn_stmt) {
        genDefers(gz, scope, cur_scope, DEFER_NORMAL_ONLY);
    }
}

// --- fullBodyExpr (AstGen.zig:2358) ---
// Processes a body expression. If it's an unlabeled block, processes
// statements inline without creating a BLOCK instruction (unlike blockExprExpr
// which wraps in BLOCK). Returns the result ref.

static uint32_t fullBodyExpr(
    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
    const Ast* tree = gz->astgen->tree;
    AstNodeTag tag = tree->nodes.tags[node];

    // Extract block statements (AstGen.zig:2368).
    AstData nd = tree->nodes.datas[node];
    uint32_t stmt_buf[2];
    const uint32_t* statements = NULL;
    uint32_t stmt_count = 0;

    switch (tag) {
    case AST_NODE_BLOCK_TWO:
    case AST_NODE_BLOCK_TWO_SEMICOLON: {
        uint32_t idx = 0;
        if (nd.lhs != 0)
            stmt_buf[idx++] = nd.lhs;
        if (nd.rhs != 0)
            stmt_buf[idx++] = nd.rhs;
        statements = stmt_buf;
        stmt_count = idx;
        break;
    }
    case AST_NODE_BLOCK:
    case AST_NODE_BLOCK_SEMICOLON: {
        uint32_t start = nd.lhs;
        uint32_t end = nd.rhs;
        statements = tree->extra_data.arr + start;
        stmt_count = end - start;
        break;
    }
    default:
        // Not a block — treat as single expression (AstGen.zig:2369).
        return exprRl(gz, scope, rl, node);
    }

    // Check if labeled (AstGen.zig:2373-2377).
    uint32_t lbrace = tree->nodes.main_tokens[node];
    bool is_labeled
        = (lbrace >= 2 && tree->tokens.tags[lbrace - 1] == TOKEN_COLON
            && tree->tokens.tags[lbrace - 2] == TOKEN_IDENTIFIER);
    if (is_labeled) {
        // Labeled blocks need a proper block instruction.
        return blockExprExpr(gz, scope, rl, node);
    }

    // Unlabeled block: process statements inline (AstGen.zig:2380-2383).
    GenZir sub_gz = makeSubBlock(gz, scope);
    blockExprStmts(&sub_gz, &sub_gz.base, statements, stmt_count);
    return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
}

// --- lastToken (Ast.zig:874) ---
// Mechanical port of Ast.lastToken. Uses iterative end_offset accumulation.

static uint32_t lastToken(const Ast* tree, uint32_t node) {
    uint32_t n = node;
    uint32_t end_offset = 0;
    while (1) {
        AstNodeTag tag = tree->nodes.tags[n];
        AstData nd = tree->nodes.datas[n];
        switch (tag) {
        case AST_NODE_ROOT:
            return tree->tokens.len - 1;

        // Binary ops: recurse into RHS (Ast.zig:893-948).
        case AST_NODE_ASSIGN_MUL:
        case AST_NODE_ASSIGN_DIV:
        case AST_NODE_ASSIGN_MOD:
        case AST_NODE_ASSIGN_ADD:
        case AST_NODE_ASSIGN_SUB:
        case AST_NODE_ASSIGN_SHL:
        case AST_NODE_ASSIGN_SHL_SAT:
        case AST_NODE_ASSIGN_SHR:
        case AST_NODE_ASSIGN_BIT_AND:
        case AST_NODE_ASSIGN_BIT_XOR:
        case AST_NODE_ASSIGN_BIT_OR:
        case AST_NODE_ASSIGN_MUL_WRAP:
        case AST_NODE_ASSIGN_ADD_WRAP:
        case AST_NODE_ASSIGN_SUB_WRAP:
        case AST_NODE_ASSIGN_MUL_SAT:
        case AST_NODE_ASSIGN_ADD_SAT:
        case AST_NODE_ASSIGN_SUB_SAT:
        case AST_NODE_ASSIGN:
        case AST_NODE_ADD:
        case AST_NODE_SUB:
        case AST_NODE_MUL:
        case AST_NODE_DIV:
        case AST_NODE_MOD:
        case AST_NODE_BIT_AND:
        case AST_NODE_BIT_OR:
        case AST_NODE_BIT_XOR:
        case AST_NODE_SHL:
        case AST_NODE_SHR:
        case AST_NODE_ARRAY_CAT:
        case AST_NODE_ARRAY_MULT:
        case AST_NODE_ADD_WRAP:
        case AST_NODE_SUB_WRAP:
        case AST_NODE_ADD_SAT:
        case AST_NODE_SUB_SAT:
        case AST_NODE_MUL_WRAP:
        case AST_NODE_MUL_SAT:
        case AST_NODE_MERGE_ERROR_SETS:
        case AST_NODE_EQUAL_EQUAL:
        case AST_NODE_BANG_EQUAL:
        case AST_NODE_LESS_THAN:
        case AST_NODE_GREATER_THAN:
        case AST_NODE_LESS_OR_EQUAL:
        case AST_NODE_GREATER_OR_EQUAL:
        case AST_NODE_BOOL_AND:
        case AST_NODE_BOOL_OR:
        case AST_NODE_ORELSE:
        case AST_NODE_CATCH:
        case AST_NODE_ERROR_UNION:
        case AST_NODE_SHL_SAT:
            n = nd.rhs;
            continue;

        // field_access: return field token + end_offset (Ast.zig:979).
        case AST_NODE_FIELD_ACCESS:
            return nd.rhs + end_offset;

        // test_decl: recurse into body node (Ast.zig:950).
        case AST_NODE_TEST_DECL:
            n = nd.rhs;
            continue;

        // defer: recurse into body (lhs) (Ast.zig:951).
        case AST_NODE_DEFER:
            n = nd.lhs;
            continue;

        // errdefer: recurse into body (rhs) (Ast.zig:950).
        case AST_NODE_ERRDEFER:
            n = nd.rhs;
            continue;

        // block (Ast.zig:1085): end_offset += 1 (rbrace), recurse into last.
        case AST_NODE_BLOCK: {
            uint32_t start = nd.lhs;
            uint32_t end = nd.rhs;
            assert(start != end);
            end_offset += 1;
            n = tree->extra_data.arr[end - 1];
            continue;
        }

        // block_semicolon (Ast.zig:1097): += 2 (semicolon + rbrace).
        case AST_NODE_BLOCK_SEMICOLON: {
            uint32_t start = nd.lhs;
            uint32_t end = nd.rhs;
            assert(start != end);
            end_offset += 2;
            n = tree->extra_data.arr[end - 1];
            continue;
        }

        // block_two (Ast.zig:1117): if rhs, recurse rhs +1; if lhs, +1; else
        // +1. Note: C parser uses 0 for "none" (OptionalIndex), not
        // UINT32_MAX.
        case AST_NODE_BLOCK_TWO: {
            if (nd.rhs != 0) {
                end_offset += 1;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 1;
                n = nd.lhs;
            } else {
                end_offset += 1;
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        }

        // block_two_semicolon (Ast.zig:1153).
        case AST_NODE_BLOCK_TWO_SEMICOLON: {
            if (nd.rhs != 0) {
                end_offset += 2;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 2;
                n = nd.lhs;
            } else {
                end_offset += 1;
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        }

        // builtin_call_two (Ast.zig:1118): recurse into args + rparen.
        case AST_NODE_BUILTIN_CALL_TWO: {
            if (nd.rhs != 0) {
                end_offset += 1;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 1;
                n = nd.lhs;
            } else {
                end_offset += 2; // lparen + rparen
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        }

        case AST_NODE_BUILTIN_CALL_TWO_COMMA: {
            if (nd.rhs != 0) {
                end_offset += 2; // comma + rparen
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 2;
                n = nd.lhs;
            } else {
                end_offset += 1;
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        }

        // Unary ops: recurse into lhs (Ast.zig:880-891).
        case AST_NODE_BOOL_NOT:
        case AST_NODE_BIT_NOT:
        case AST_NODE_NEGATION:
        case AST_NODE_NEGATION_WRAP:
        case AST_NODE_ADDRESS_OF:
        case AST_NODE_TRY:
        case AST_NODE_AWAIT:
        case AST_NODE_OPTIONAL_TYPE:
        case AST_NODE_SUSPEND:
        case AST_NODE_COMPTIME:
        case AST_NODE_NOSUSPEND:
        case AST_NODE_RESUME:
            n = nd.lhs;
            continue;

        // return: optional operand (Ast.zig:998-1002).
        case AST_NODE_RETURN:
            if (nd.lhs != 0) {
                n = nd.lhs;
                continue;
            }
            return tree->nodes.main_tokens[n] + end_offset;

        // deref: main_token is the `.*` token (Ast.zig:993).
        case AST_NODE_DEREF:
            return tree->nodes.main_tokens[n] + end_offset;

        // unwrap_optional (Ast.zig:980): return rhs token + end_offset.
        case AST_NODE_UNWRAP_OPTIONAL:
            return nd.rhs + end_offset;

        // for_range (Ast.zig:973-977): recurse into rhs if present, else
        // main_token + end_offset.
        case AST_NODE_FOR_RANGE:
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;

        // error_value: main_token is `error`, last token is name (+2)
        // (Ast.zig:986).
        case AST_NODE_ERROR_VALUE:
            return tree->nodes.main_tokens[n] + 2 + end_offset;

        // Terminals: return main_token + end_offset (Ast.zig:988-996).
        case AST_NODE_NUMBER_LITERAL:
        case AST_NODE_STRING_LITERAL:
        case AST_NODE_IDENTIFIER:
        case AST_NODE_ENUM_LITERAL:
        case AST_NODE_CHAR_LITERAL:
        case AST_NODE_UNREACHABLE_LITERAL:
        case AST_NODE_ANYFRAME_LITERAL:
            return tree->nodes.main_tokens[n] + end_offset;

        // call_one (Ast.zig:1107-1114): +1 for rparen, recurse into
        // first_param if present.
        case AST_NODE_CALL_ONE:
            end_offset += 1; // rparen
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        case AST_NODE_CALL_ONE_COMMA:
            end_offset += 2; // comma + rparen
            n = nd.rhs;
            continue;

        // array_access: end_offset += 1 (rbracket), recurse rhs.
        case AST_NODE_ARRAY_ACCESS:
            end_offset += 1;
            n = nd.rhs;
            continue;

        // simple_var_decl: recurse into init/type (Ast.zig:1169-1178).
        case AST_NODE_SIMPLE_VAR_DECL:
            if (nd.rhs != 0) {
                n = nd.rhs; // init expr
            } else if (nd.lhs != 0) {
                n = nd.lhs; // type expr
            } else {
                end_offset += 1; // from mut token to name
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;

        // aligned_var_decl: recurse into init/align (Ast.zig:1180-1187).
        case AST_NODE_ALIGNED_VAR_DECL:
            if (nd.rhs != 0) {
                n = nd.rhs; // init expr
            } else {
                end_offset += 1; // rparen
                n = nd.lhs; // align expr
            }
            continue;

        // local_var_decl (Ast.zig:1209-1217).
        // extra[lhs] = LocalVarDecl { type_node, align_node }
        case AST_NODE_LOCAL_VAR_DECL:
            if (nd.rhs != 0) {
                n = nd.rhs; // init expr
            } else {
                end_offset += 1; // rparen
                n = tree->extra_data.arr[nd.lhs + 1]; // align_node
            }
            continue;

        // global_var_decl (Ast.zig:1189-1207).
        // extra[lhs] = GlobalVarDecl { type_node, align_node,
        //                              addrspace_node, section_node }
        case AST_NODE_GLOBAL_VAR_DECL:
            if (nd.rhs != 0) {
                n = nd.rhs; // init expr
            } else {
                uint32_t section_node = tree->extra_data.arr[nd.lhs + 3];
                uint32_t align_node = tree->extra_data.arr[nd.lhs + 1];
                uint32_t type_node = tree->extra_data.arr[nd.lhs];
                if (section_node != 0) {
                    end_offset += 1; // rparen
                    n = section_node;
                } else if (align_node != 0) {
                    end_offset += 1; // rparen
                    n = align_node;
                } else if (type_node != 0) {
                    n = type_node;
                } else {
                    end_offset += 1; // from mut token to name
                    return tree->nodes.main_tokens[n] + end_offset;
                }
            }
            continue;

        // slice_open: end_offset += 2 (ellipsis2 + rbracket), recurse rhs
        // (Ast.zig:1245-1248).
        case AST_NODE_SLICE_OPEN:
            end_offset += 2;
            n = nd.rhs;
            continue;

        // grouped_expression (Ast.zig:983): return rhs token + end_offset.
        case AST_NODE_GROUPED_EXPRESSION:
            return nd.rhs + end_offset;

        // if_simple: recurse into body (rhs) (Ast.zig:942).
        case AST_NODE_IF_SIMPLE:
        case AST_NODE_WHILE_SIMPLE:
        case AST_NODE_FOR_SIMPLE:
        case AST_NODE_FN_DECL:
        case AST_NODE_ARRAY_TYPE:
            n = nd.rhs;
            continue;

        // if: recurse into else_expr (Ast.zig:1295).
        case AST_NODE_IF: {
            // If[rhs]: { then_expr, else_expr }
            n = tree->extra_data.arr[nd.rhs + 1]; // else_expr
            continue;
        }

        // while: recurse into else_expr (Ast.zig:1290).
        case AST_NODE_WHILE: {
            // While[rhs]: { cont_expr, then_expr, else_expr }
            n = tree->extra_data.arr[nd.rhs + 2]; // else_expr
            continue;
        }

        // while_cont: recurse into then_expr (Ast.zig:943-like).
        case AST_NODE_WHILE_CONT: {
            // WhileCont[rhs]: { cont_expr, then_expr }
            n = tree->extra_data.arr[nd.rhs + 1]; // then_expr
            continue;
        }

        // switch: recurse into last case (Ast.zig:1031-1041).
        case AST_NODE_SWITCH: {
            uint32_t ei = nd.rhs;
            uint32_t cs = tree->extra_data.arr[ei];
            uint32_t ce = tree->extra_data.arr[ei + 1];
            if (cs == ce) {
                end_offset += 3; // rparen, lbrace, rbrace
                n = nd.lhs;
            } else {
                end_offset += 1; // rbrace
                n = tree->extra_data.arr[ce - 1];
            }
            continue;
        }
        case AST_NODE_SWITCH_COMMA: {
            uint32_t ei = nd.rhs;
            uint32_t cs = tree->extra_data.arr[ei];
            uint32_t ce = tree->extra_data.arr[ei + 1];
            assert(cs != ce);
            end_offset += 2; // comma + rbrace
            n = tree->extra_data.arr[ce - 1];
            continue;
        }

        // switch_case_one: recurse into rhs (body) (Ast.zig:942).
        case AST_NODE_SWITCH_CASE_ONE:
        case AST_NODE_SWITCH_CASE_INLINE_ONE:
        case AST_NODE_SWITCH_CASE:
        case AST_NODE_SWITCH_CASE_INLINE:
            n = nd.rhs;
            continue;

        // switch_range: recurse into rhs (Ast.zig: binary op pattern).
        case AST_NODE_SWITCH_RANGE:
            n = nd.rhs;
            continue;

        // struct_init_one: recurse into field if present, +1.
        case AST_NODE_STRUCT_INIT_ONE:
            end_offset += 1; // rbrace
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        case AST_NODE_STRUCT_INIT_ONE_COMMA:
            end_offset += 2; // comma + rbrace
            n = nd.rhs;
            continue;

        // struct_init_dot_two: similar to block_two.
        case AST_NODE_STRUCT_INIT_DOT_TWO:
            if (nd.rhs != 0) {
                end_offset += 1;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 1;
                n = nd.lhs;
            } else {
                end_offset += 1; // rbrace
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA:
            end_offset += 2;
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                n = nd.lhs;
            }
            continue;

        // struct_init_dot: SubRange pattern.
        case AST_NODE_STRUCT_INIT_DOT:
            assert(nd.lhs != nd.rhs);
            end_offset += 1;
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;

        // struct_init: node_and_extra SubRange pattern.
        case AST_NODE_STRUCT_INIT: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 1;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // call: SubRange pattern.
        case AST_NODE_CALL: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 1;
            n = tree->extra_data.arr[se - 1];
            continue;
        }
        case AST_NODE_CALL_COMMA: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // fn_proto_simple: recurse into rhs (return type).
        case AST_NODE_FN_PROTO_SIMPLE:
        case AST_NODE_FN_PROTO_ONE:
        case AST_NODE_FN_PROTO_MULTI:
        case AST_NODE_FN_PROTO:
            n = nd.rhs;
            continue;

        // error_set_decl: rhs is the closing rbrace token.
        case AST_NODE_ERROR_SET_DECL:
            return nd.rhs + end_offset;

        // ptr_type variants: recurse into rhs (child type).
        case AST_NODE_PTR_TYPE_ALIGNED:
        case AST_NODE_PTR_TYPE_SENTINEL:
        case AST_NODE_PTR_TYPE:
        case AST_NODE_PTR_TYPE_BIT_RANGE:
            n = nd.rhs;
            continue;

        // container_decl: extra_range pattern.
        case AST_NODE_CONTAINER_DECL:
        case AST_NODE_TAGGED_UNION:
            assert(nd.lhs != nd.rhs);
            end_offset += 1;
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;
        case AST_NODE_CONTAINER_DECL_TRAILING:
        case AST_NODE_TAGGED_UNION_TRAILING:
            assert(nd.lhs != nd.rhs);
            end_offset += 2;
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;

        // container_decl_two / tagged_union_two (Ast.zig:1120-1151).
        case AST_NODE_CONTAINER_DECL_TWO:
        case AST_NODE_TAGGED_UNION_TWO:
            if (nd.rhs != 0) {
                end_offset += 1;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 1;
                n = nd.lhs;
            } else {
                if (tag == AST_NODE_CONTAINER_DECL_TWO) {
                    uint32_t i = 2; // lbrace + rbrace
                    while (tree->tokens.tags[tree->nodes.main_tokens[n] + i]
                        == TOKEN_CONTAINER_DOC_COMMENT)
                        i += 1;
                    end_offset += i;
                } else {
                    // tagged_union_two: (enum) {}
                    uint32_t i = 5;
                    while (tree->tokens.tags[tree->nodes.main_tokens[n] + i]
                        == TOKEN_CONTAINER_DOC_COMMENT)
                        i += 1;
                    end_offset += i;
                }
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
        case AST_NODE_TAGGED_UNION_TWO_TRAILING:
            end_offset += 2;
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                n = nd.lhs;
            }
            continue;

        // container_decl_arg: node_and_extra SubRange.
        case AST_NODE_CONTAINER_DECL_ARG: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            if (si == se) {
                end_offset += 3; // rparen + lbrace + rbrace
                n = nd.lhs;
            } else {
                end_offset += 1;
                n = tree->extra_data.arr[se - 1];
            }
            continue;
        }
        case AST_NODE_CONTAINER_DECL_ARG_TRAILING: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // slice: extra data pattern.
        case AST_NODE_SLICE: {
            // Slice[rhs]: { start, end }
            end_offset += 1;
            n = tree->extra_data.arr[nd.rhs + 1]; // end
            continue;
        }
        case AST_NODE_SLICE_SENTINEL: {
            // SliceSentinel[rhs]: { start, end, sentinel }
            end_offset += 1;
            n = tree->extra_data.arr[nd.rhs + 2]; // sentinel
            continue;
        }

        // array_type_sentinel: extra data.
        case AST_NODE_ARRAY_TYPE_SENTINEL: {
            // ArrayTypeSentinel[rhs]: { sentinel, elem_type }
            n = tree->extra_data.arr[nd.rhs + 1]; // elem_type
            continue;
        }

        // multiline_string_literal: main_token + end_offset.
        case AST_NODE_MULTILINE_STRING_LITERAL:
            return nd.rhs + end_offset;

        // break/continue (Ast.zig:1275-1283).
        // lhs is opt_token (null_token = UINT32_MAX), rhs is opt_node (0 =
        // none).
        case AST_NODE_BREAK:
        case AST_NODE_CONTINUE:
            if (nd.rhs != 0) {
                n = nd.rhs; // optional rhs expression
            } else if (nd.lhs != UINT32_MAX) {
                return nd.lhs + end_offset; // label token
            } else {
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;

        // array_init_one: end_offset += 1 (rbrace), recurse rhs
        // (Ast.zig:1224-1230).
        case AST_NODE_ARRAY_INIT_ONE:
            end_offset += 1;
            n = nd.rhs;
            continue;

        case AST_NODE_ARRAY_INIT_ONE_COMMA:
            end_offset += 2; // comma + rbrace
            n = nd.rhs;
            continue;

        // struct_init_dot_comma: SubRange pattern.
        case AST_NODE_STRUCT_INIT_DOT_COMMA:
            assert(nd.lhs != nd.rhs);
            end_offset += 2; // comma + rbrace
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;

        // struct_init_comma: node_and_extra SubRange.
        case AST_NODE_STRUCT_INIT_COMMA: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // array_init variants.
        case AST_NODE_ARRAY_INIT: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 1;
            n = tree->extra_data.arr[se - 1];
            continue;
        }
        case AST_NODE_ARRAY_INIT_COMMA: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // array_init_dot variants.
        case AST_NODE_ARRAY_INIT_DOT_TWO:
            if (nd.rhs != 0) {
                end_offset += 1;
                n = nd.rhs;
            } else if (nd.lhs != 0) {
                end_offset += 1;
                n = nd.lhs;
            } else {
                end_offset += 1;
                return tree->nodes.main_tokens[n] + end_offset;
            }
            continue;
        case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA:
            end_offset += 2;
            if (nd.rhs != 0) {
                n = nd.rhs;
            } else {
                n = nd.lhs;
            }
            continue;
        case AST_NODE_ARRAY_INIT_DOT:
            assert(nd.lhs != nd.rhs);
            end_offset += 1;
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;
        case AST_NODE_ARRAY_INIT_DOT_COMMA:
            assert(nd.lhs != nd.rhs);
            end_offset += 2;
            n = tree->extra_data.arr[nd.rhs - 1];
            continue;

        // builtin_call (Ast.zig:1083-1105).
        case AST_NODE_BUILTIN_CALL: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 1;
            n = tree->extra_data.arr[se - 1];
            continue;
        }
        case AST_NODE_BUILTIN_CALL_COMMA: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2;
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        // for (Ast.zig:1300-1303): complex extra data.
        case AST_NODE_FOR: {
            // lhs = span.start (extra_data index),
            // rhs = packed(inputs:u31, has_else:u1 at bit 31).
            // extra[lhs..] = input nodes, then_body, [else_body].
            uint32_t span_start = nd.lhs;
            uint32_t for_packed = nd.rhs;
            uint32_t inputs = for_packed & 0x7FFFFFFFu;
            bool has_else = (for_packed >> 31) != 0;
            uint32_t last_idx = span_start + inputs + (has_else ? 1 : 0);
            n = tree->extra_data.arr[last_idx];
            continue;
        }

        // anyframe_type (Ast.zig:952): recurse into rhs.
        case AST_NODE_ANYFRAME_TYPE:
            n = nd.rhs;
            continue;

        // assign_destructure (Ast.zig:960-965): recurse into rhs.
        case AST_NODE_ASSIGN_DESTRUCTURE:
            n = nd.rhs;
            continue;

        // asm_simple (Ast.zig:981): return nd.rhs + end_offset.
        case AST_NODE_ASM_SIMPLE:
            return nd.rhs + end_offset;

        // asm_input (Ast.zig:983): return nd.rhs + end_offset.
        case AST_NODE_ASM_INPUT:
            return nd.rhs + end_offset;

        // asm_output (Ast.zig:985): return nd.rhs + end_offset.
        case AST_NODE_ASM_OUTPUT:
            return nd.rhs + end_offset;

        // asm_legacy (Ast.zig:1053-1057): read rparen from extra data.
        case AST_NODE_ASM_LEGACY: {
            // extra[rhs] = AsmLegacy { items_start, items_end, rparen }
            uint32_t rparen = tree->extra_data.arr[nd.rhs + 2];
            return rparen + end_offset;
        }

        // asm (Ast.zig:1058-1062): read rparen from extra data.
        case AST_NODE_ASM: {
            // extra[rhs] = Asm { items_start, items_end, clobbers, rparen }
            uint32_t rparen = tree->extra_data.arr[nd.rhs + 3];
            return rparen + end_offset;
        }

        // container_field_init (Ast.zig:1219-1222): recurse into
        // value_expr or type_expr.
        case AST_NODE_CONTAINER_FIELD_INIT:
            if (nd.rhs != 0) {
                n = nd.rhs; // value_expr
            } else {
                n = nd.lhs; // type_expr
            }
            continue;

        // container_field_align (Ast.zig:1224-1231): +1 for rparen,
        // recurse rhs.
        case AST_NODE_CONTAINER_FIELD_ALIGN:
            end_offset += 1;
            n = nd.rhs;
            continue;

        // container_field (Ast.zig:1232-1236): read value_expr from
        // extra data.
        case AST_NODE_CONTAINER_FIELD: {
            // extra[rhs] = ContainerField { align_expr, value_expr }
            uint32_t value_expr = tree->extra_data.arr[nd.rhs + 1];
            n = value_expr;
            continue;
        }

        // tagged_union_enum_tag (Ast.zig:1011-1021): SubRange handling.
        case AST_NODE_TAGGED_UNION_ENUM_TAG: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            if (si == se) {
                end_offset += 4; // rparen + rparen + lbrace + rbrace
                n = nd.lhs;
            } else {
                end_offset += 1; // rbrace
                n = tree->extra_data.arr[se - 1];
            }
            continue;
        }
        // tagged_union_enum_tag_trailing (Ast.zig:1022-1030).
        case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING: {
            uint32_t si = tree->extra_data.arr[nd.rhs];
            uint32_t se = tree->extra_data.arr[nd.rhs + 1];
            assert(si != se);
            end_offset += 2; // comma/semicolon + rbrace
            n = tree->extra_data.arr[se - 1];
            continue;
        }

        default:
            // Fallback: return main_token + end_offset.
            return tree->nodes.main_tokens[n] + end_offset;
        }
    }
}

// --- addParam (AstGen.zig:12390) ---
// Creates a param instruction with pl_tok data and type body in extra.

static uint32_t addParam(GenZir* gz, GenZir* param_gz, ZirInstTag tag,
    uint32_t abs_tok_index, uint32_t name, bool is_generic) {
    AstGenCtx* ag = gz->astgen;

    uint32_t body_len = gzInstructionsLen(param_gz);
    const uint32_t* param_body = gzInstructionsSlice(param_gz);

    // Param payload: name, type{body_len:u31|is_generic:u1}
    ensureExtraCapacity(ag, 2 + body_len);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = name;
    ag->extra[ag->extra_len++]
        = (body_len & 0x7FFFFFFFu) | (is_generic ? 0x80000000u : 0u);
    for (uint32_t i = 0; i < body_len; i++) {
        ag->extra[ag->extra_len++] = param_body[i];
    }
    gzUnstack(param_gz);

    // Emit the param instruction.
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = tag;
    ZirInstData data;
    data.pl_tok.src_tok = tokenIndexToRelative(gz, abs_tok_index);
    data.pl_tok.payload_index = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx;
}

// --- addDbgVar (AstGen.zig:13196) ---

static void addDbgVar(
    GenZir* gz, ZirInstTag tag, uint32_t name, uint32_t inst) {
    if (gz->is_comptime)
        return;
    ZirInstData data;
    data.str_op.str = name;
    data.str_op.operand = inst;
    addInstruction(gz, tag, data);
}

// --- addFunc (AstGen.zig:12023) ---
// Handles non-fancy func/func_inferred instructions.
// ret_body/ret_body_len: instructions for the return type sub-block (may be
// 0). ret_ref: if ret_body_len==0, the return type as a simple Ref.

static uint32_t addFunc(GenZir* gz, uint32_t src_node, uint32_t block_node,
    uint32_t param_block, uint32_t ret_ref, const uint32_t* ret_body,
    uint32_t ret_body_len, const uint32_t* body, uint32_t body_len,
    const uint32_t* param_insts, uint32_t param_insts_len,
    uint32_t lbrace_line, uint32_t lbrace_column, bool is_inferred_error,
    bool ret_ty_is_generic, const uint32_t* ret_param_refs,
    uint32_t ret_param_refs_len) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    uint32_t rbrace_tok = lastToken(tree, block_node);
    uint32_t rbrace_start = tree->tokens.starts[rbrace_tok];
    advanceSourceCursor(ag, rbrace_start);
    uint32_t rbrace_line = ag->source_line - gz->decl_line;
    uint32_t rbrace_column = ag->source_column;

    // Build Func payload (Zir.Inst.Func: ret_ty, param_block, body_len).
    // (AstGen.zig:12182-12194)
    uint32_t ret_ty_packed_len;
    if (ret_body_len > 0) {
        ret_ty_packed_len
            = countBodyLenAfterFixups(ag, ret_param_refs, ret_param_refs_len)
            + countBodyLenAfterFixups(ag, ret_body, ret_body_len);
    } else if (ret_ref != ZIR_REF_NONE) {
        ret_ty_packed_len = 1; // simple Ref
    } else {
        ret_ty_packed_len = 0; // void return
    }
    // Pack RetTy: body_len:u31 | is_generic:bool(u1).
    uint32_t ret_ty_packed = (ret_ty_packed_len & 0x7FFFFFFFu)
        | (ret_ty_is_generic ? 0x80000000u : 0u);

    uint32_t fixup_body_len = countBodyLenAfterFixupsExtraRefs(
        ag, body, body_len, param_insts, param_insts_len);
    ensureExtraCapacity(ag, 3 + ret_ty_packed_len + fixup_body_len + 7);
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = ret_ty_packed; // Func.ret_ty
    ag->extra[ag->extra_len++] = param_block; // Func.param_block
    ag->extra[ag->extra_len++] = fixup_body_len; // Func.body_len

    // Trailing ret_ty: either body instructions (with ret_param_refs
    // prepended) or a single ref. (AstGen.zig:12196-12204)
    if (ret_body_len > 0) {
        appendBodyWithFixups(ag, ret_param_refs, ret_param_refs_len);
        appendBodyWithFixups(ag, ret_body, ret_body_len);
    } else if (ret_ref != ZIR_REF_NONE) {
        ag->extra[ag->extra_len++] = ret_ref;
    }

    // Body instructions with extra_refs for param_insts
    // (AstGen.zig:12206).
    appendBodyWithFixupsExtraRefs(
        ag, body, body_len, param_insts, param_insts_len);

    // SrcLocs (AstGen.zig:12098-12106).
    uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
    ag->extra[ag->extra_len++] = lbrace_line;
    ag->extra[ag->extra_len++] = rbrace_line;
    ag->extra[ag->extra_len++] = columns;
    // proto_hash (4 words): zero for now.
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;

    // Emit the func instruction (AstGen.zig:12220-12226).
    ZirInstTag tag
        = is_inferred_error ? ZIR_INST_FUNC_INFERRED : ZIR_INST_FUNC;
    ZirInstData data;
    data.pl_node.src_node = (int32_t)src_node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    return addInstruction(gz, tag, data);
}

// --- addFuncFancy (AstGen.zig:12112-12173) ---
// Emits func_fancy instruction when cc_ref, is_var_args, noalias_bits,
// or is_noinline are present.

static uint32_t addFuncFancy(GenZir* gz, uint32_t src_node,
    uint32_t block_node, uint32_t param_block, uint32_t ret_ref,
    const uint32_t* ret_body, uint32_t ret_body_len, uint32_t cc_ref,
    const uint32_t* cc_body, uint32_t cc_body_len, const uint32_t* body,
    uint32_t body_len, const uint32_t* param_insts, uint32_t param_insts_len,
    uint32_t lbrace_line, uint32_t lbrace_column, bool is_var_args,
    bool is_inferred_error, bool is_noinline, uint32_t noalias_bits,
    bool ret_ty_is_generic, const uint32_t* ret_param_refs,
    uint32_t ret_param_refs_len) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    uint32_t rbrace_tok = lastToken(tree, block_node);
    uint32_t rbrace_start = tree->tokens.starts[rbrace_tok];
    advanceSourceCursor(ag, rbrace_start);
    uint32_t rbrace_line = ag->source_line - gz->decl_line;
    uint32_t rbrace_column = ag->source_column;

    uint32_t fixup_body_len = countBodyLenAfterFixupsExtraRefs(
        ag, body, body_len, param_insts, param_insts_len);

    // Calculate cc extra len (AstGen.zig:12231-12236).
    uint32_t cc_extra_len = 0;
    if (cc_body_len > 0) {
        cc_extra_len = countBodyLenAfterFixups(ag, cc_body, cc_body_len) + 1;
    } else if (cc_ref != ZIR_REF_NONE) {
        cc_extra_len = 1;
    }

    // Calculate ret extra len (AstGen.zig:12231-12236).
    uint32_t ret_extra_len = 0;
    if (ret_body_len > 0) {
        ret_extra_len
            = countBodyLenAfterFixups(ag, ret_param_refs, ret_param_refs_len)
            + countBodyLenAfterFixups(ag, ret_body, ret_body_len) + 1;
    } else if (ret_ref != ZIR_REF_NONE) {
        ret_extra_len = 1;
    }

    // FuncFancy has 3 fields: param_block, body_len, bits.
    uint32_t total_extra = 3 + cc_extra_len + ret_extra_len
        + ((noalias_bits != 0) ? 1u : 0u) + fixup_body_len + 7;
    ensureExtraCapacity(ag, total_extra);

    // FuncFancy payload (Zir.zig:2589-2610).
    uint32_t payload_index = ag->extra_len;
    ag->extra[ag->extra_len++] = param_block;
    ag->extra[ag->extra_len++] = fixup_body_len;
    // Bits packed as u32 (Zir.zig:2598-2609).
    uint32_t bits = 0;
    if (is_var_args)
        bits |= (1u << 0);
    if (is_inferred_error)
        bits |= (1u << 1);
    if (is_noinline)
        bits |= (1u << 2);
    if (cc_ref != ZIR_REF_NONE)
        bits |= (1u << 3); // has_cc_ref
    if (cc_body_len > 0)
        bits |= (1u << 4); // has_cc_body
    if (ret_ref != ZIR_REF_NONE)
        bits |= (1u << 5); // has_ret_ty_ref
    if (ret_body_len > 0)
        bits |= (1u << 6); // has_ret_ty_body
    if (noalias_bits != 0)
        bits |= (1u << 7); // has_any_noalias
    if (ret_ty_is_generic)
        bits |= (1u << 8); // ret_ty_is_generic
    ag->extra[ag->extra_len++] = bits;

    // Trailing cc (AstGen.zig:12143-12151).
    if (cc_body_len > 0) {
        ag->extra[ag->extra_len++]
            = countBodyLenAfterFixups(ag, cc_body, cc_body_len);
        for (uint32_t i = 0; i < cc_body_len; i++)
            appendPossiblyRefdBodyInst(ag, cc_body[i]);
    } else if (cc_ref != ZIR_REF_NONE) {
        ag->extra[ag->extra_len++] = cc_ref;
    }

    // Trailing ret_ty (AstGen.zig:12152-12164).
    if (ret_body_len > 0) {
        ag->extra[ag->extra_len++]
            = countBodyLenAfterFixups(ag, ret_param_refs, ret_param_refs_len)
            + countBodyLenAfterFixups(ag, ret_body, ret_body_len);
        appendBodyWithFixups(ag, ret_param_refs, ret_param_refs_len);
        appendBodyWithFixups(ag, ret_body, ret_body_len);
    } else if (ret_ref != ZIR_REF_NONE) {
        ag->extra[ag->extra_len++] = ret_ref;
    }

    // Trailing noalias_bits (AstGen.zig:12166-12168).
    if (noalias_bits != 0)
        ag->extra[ag->extra_len++] = noalias_bits;

    // Body (AstGen.zig:12170).
    appendBodyWithFixupsExtraRefs(
        ag, body, body_len, param_insts, param_insts_len);

    // SrcLocs (AstGen.zig:12098-12106).
    uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
    ag->extra[ag->extra_len++] = lbrace_line;
    ag->extra[ag->extra_len++] = rbrace_line;
    ag->extra[ag->extra_len++] = columns;
    // proto_hash (4 words): zero for now.
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;

    // Emit the func_fancy instruction (AstGen.zig:12220-12226).
    ZirInstData data;
    data.pl_node.src_node = (int32_t)src_node - (int32_t)gz->decl_node_index;
    data.pl_node.payload_index = payload_index;
    return addInstruction(gz, ZIR_INST_FUNC_FANCY, data);
}

// --- testDecl (AstGen.zig:4708) ---

static void testDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
    uint32_t* wip_decl_insts, uint32_t* decl_idx, uint32_t node) {
    const Ast* tree = ag->tree;
    AstData nd = tree->nodes.datas[node];
    uint32_t body_node = nd.rhs;

    // makeDeclaration before advanceSourceCursorToNode (AstGen.zig:4726-4729).
    uint32_t decl_inst = makeDeclaration(ag, node);
    wip_decl_insts[*decl_idx] = decl_inst;
    (*decl_idx)++;
    advanceSourceCursorToNode(ag, node);

    uint32_t decl_line = ag->source_line;
    uint32_t decl_column = ag->source_column;

    // Extract test name (AstGen.zig:4748-4835).
    uint32_t test_token = tree->nodes.main_tokens[node];
    uint32_t test_name_token = test_token + 1;
    uint32_t test_name = 0; // NullTerminatedString.empty
    DeclFlagsId decl_id = DECL_ID_UNNAMED_TEST;

    // Check if the token after 'test' is a string literal.
    // We identify string literals by checking the source character.
    uint32_t name_tok_start = tree->tokens.starts[test_name_token];
    if (name_tok_start < tree->source_len
        && tree->source[name_tok_start] == '"') {
        // String literal name.
        uint32_t name_len;
        strLitAsString(ag, test_name_token, &test_name, &name_len);
        decl_id = DECL_ID_TEST;
    } else if (tree->tokens.tags[test_name_token] == TOKEN_IDENTIFIER) {
        // Identifier test name (decltest) (AstGen.zig:4763-4834).
        // Upstream performs full scope resolution for validation; we skip
        // the validation and just record the identifier as the test name.
        test_name = identAsString(ag, test_name_token);
        decl_id = DECL_ID_DECLTEST;
    }

    // Set up decl_block GenZir (AstGen.zig:4735-4743).
    GenZir decl_block;
    memset(&decl_block, 0, sizeof(decl_block));
    decl_block.base.tag = SCOPE_GEN_ZIR;
    decl_block.parent = scope;
    decl_block.astgen = ag;
    decl_block.decl_node_index = node;
    decl_block.decl_line = decl_line;
    decl_block.is_comptime = true;
    decl_block.instructions_top = ag->scratch_inst_len;
    decl_block.break_block = UINT32_MAX;
    decl_block.any_defer_node = UINT32_MAX;

    // Set up fn_block GenZir (AstGen.zig:4837-4845).
    GenZir fn_block;
    memset(&fn_block, 0, sizeof(fn_block));
    fn_block.base.tag = SCOPE_GEN_ZIR;
    fn_block.parent = &decl_block.base;
    fn_block.astgen = ag;
    fn_block.decl_node_index = node;
    fn_block.decl_line = decl_line;
    fn_block.is_comptime = false;
    fn_block.instructions_top = ag->scratch_inst_len;
    fn_block.break_block = UINT32_MAX;
    fn_block.any_defer_node = UINT32_MAX;

    // Set within_fn, fn_block and fn_ret_ty for the body
    // (AstGen.zig:4848-4853).
    bool prev_within_fn = ag->within_fn;
    void* prev_fn_block = ag->fn_block;
    uint32_t prev_fn_ret_ty = ag->fn_ret_ty;
    ag->within_fn = true;
    setFnBlock(ag, &fn_block);
    ag->fn_ret_ty = ZIR_REF_ANYERROR_VOID_ERROR_UNION_TYPE;

    // Compute lbrace source location (AstGen.zig:4860-4862).
    advanceSourceCursorToNode(ag, body_node);
    uint32_t lbrace_line = ag->source_line - decl_line;
    uint32_t lbrace_column = ag->source_column;

    // Process test body (AstGen.zig:4864).
    uint32_t block_result
        = fullBodyExpr(&fn_block, &fn_block.base, RL_NONE_VAL, body_node);

    ag->within_fn = prev_within_fn;
    ag->fn_block = prev_fn_block;
    ag->fn_ret_ty = prev_fn_ret_ty;

    // If we hit unimplemented features, bail out.
    if (ag->has_compile_errors)
        return;

    // Add restore_err_ret_index + ret_implicit (AstGen.zig:4865-4871).
    if (gzInstructionsLen(&fn_block) == 0
        || !refIsNoReturn(&fn_block, block_result)) {
        ZirInstData rdata;
        rdata.un_node.operand = ZIR_REF_NONE; // .none for .ret
        rdata.un_node.src_node
            = (int32_t)node - (int32_t)fn_block.decl_node_index;
        addInstruction(
            &fn_block, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);

        uint32_t body_last_tok = lastToken(tree, body_node);
        ZirInstData rdata2;
        rdata2.un_tok.operand = ZIR_REF_VOID_VALUE;
        rdata2.un_tok.src_tok = tokenIndexToRelative(&fn_block, body_last_tok);
        addInstruction(&fn_block, ZIR_INST_RET_IMPLICIT, rdata2);
    }

    // Read fn_block body before unstacking (AstGen.zig:4874).
    // Upstream unstacks fn_block inside addFunc before appending the func
    // instruction to decl_block. We must unstack fn_block first so that
    // addFunc's addInstruction goes into decl_block's range.
    const uint32_t* fn_body = gzInstructionsSlice(&fn_block);
    uint32_t fn_body_len = gzInstructionsLen(&fn_block);
    gzUnstack(&fn_block);

    // Create func instruction (AstGen.zig:4874-4897).
    uint32_t func_ref = addFunc(&decl_block, node, body_node, decl_inst,
        ZIR_REF_ANYERROR_VOID_ERROR_UNION_TYPE, NULL, 0, fn_body, fn_body_len,
        NULL, 0, lbrace_line, lbrace_column, false, false, NULL, 0);

    // break_inline returning func to declaration (AstGen.zig:4899).
    makeBreakInline(&decl_block, decl_inst, func_ref, AST_NODE_OFFSET_NONE);

    // setDeclaration (AstGen.zig:4903-4923).
    setDeclaration(ag, decl_inst,
        (SetDeclArgs) { .src_line = decl_line,
            .src_column = decl_column,
            .id = decl_id,
            .name = test_name,
            .lib_name = UINT32_MAX,
            .value_body = gzInstructionsSlice(&decl_block),
            .value_body_len = gzInstructionsLen(&decl_block) });
    gzUnstack(&decl_block);

    (void)gz;
}

// --- fnDecl (AstGen.zig:4067) / fnDeclInner (AstGen.zig:4228) ---
// Handles function declarations with bodies (fn_decl) and
// function prototypes without bodies (fn_proto*).

static void fnDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
    uint32_t* wip_decl_insts, uint32_t* decl_idx, uint32_t node) {
    const Ast* tree = ag->tree;
    AstNodeTag node_tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // For fn_decl: data.lhs = fn_proto node, data.rhs = body node.
    // For fn_proto*: the node itself IS the proto, no body.
    uint32_t proto_node;
    uint32_t body_node;
    if (node_tag == AST_NODE_FN_DECL) {
        proto_node = nd.lhs;
        body_node = nd.rhs;
    } else {
        // fn_proto_simple, fn_proto_multi, fn_proto_one, fn_proto
        proto_node = node;
        body_node = 0;
    }

    // Get function name token (main_token of proto + 1 = fn name).
    uint32_t fn_token = tree->nodes.main_tokens[proto_node];
    uint32_t fn_name_token = fn_token + 1;

    // Check for 'pub', 'export', 'inline', 'noinline' modifiers
    // (Ast.zig:2003-2025, AstGen.zig:4102-4106, 4240-4247).
    bool is_pub = false;
    bool is_export = false;
    bool is_noinline = false;
    bool has_inline_keyword = false;
    for (uint32_t i = fn_token; i > 0;) {
        i--;
        uint32_t ttag = tree->tokens.tags[i];
        if (ttag == TOKEN_KEYWORD_PUB)
            is_pub = true;
        else if (ttag == TOKEN_KEYWORD_EXPORT)
            is_export = true;
        else if (ttag == TOKEN_KEYWORD_NOINLINE)
            is_noinline = true;
        else if (ttag == TOKEN_KEYWORD_INLINE)
            has_inline_keyword = true;
        else
            break;
    }

    // makeDeclaration on fn_proto node (AstGen.zig:4090).
    uint32_t decl_inst = makeDeclaration(ag, proto_node);
    wip_decl_insts[*decl_idx] = decl_inst;
    (*decl_idx)++;

    advanceSourceCursorToNode(ag, node);
    uint32_t decl_line = ag->source_line;
    uint32_t decl_column = ag->source_column;

    // Set this now, since parameter types, return type, etc may be generic
    // (AstGen.zig:4097-4100).
    bool prev_within_fn = ag->within_fn;
    ag->within_fn = true;

    // Save source cursor for restoring after ret_gz (AstGen.zig:4387-4388).
    uint32_t saved_source_offset = ag->source_offset;
    uint32_t saved_source_line = ag->source_line;
    uint32_t saved_source_column = ag->source_column;

    AstNodeTag proto_tag = tree->nodes.tags[proto_node];
    AstData proto_data = tree->nodes.datas[proto_node];

    // Extract return type node (rhs for all fn_proto variants).
    uint32_t return_type_node = proto_data.rhs;

    // Detect inferred error set: token before return type is '!'
    // (AstGen.zig:4249-4251).
    bool is_inferred_error = false;
    if (return_type_node != 0) {
        uint32_t ret_first_tok = firstToken(tree, return_type_node);
        if (ret_first_tok > 0) {
            uint32_t maybe_bang = ret_first_tok - 1;
            uint32_t bang_start = tree->tokens.starts[maybe_bang];
            if (tree->source[bang_start] == '!')
                is_inferred_error = true;
        }
    }

    // Extract param type nodes and callconv_expr from proto variant
    // (AstGen.zig:4253-4254, Ast.zig:1456-1520).
    uint32_t param_nodes_buf[1]; // buffer for fn_proto_simple/fn_proto_one
    const uint32_t* param_nodes = NULL;
    uint32_t params_len = 0;
    uint32_t callconv_expr_node = 0; // 0 = none (OptionalIndex)

    if (proto_tag == AST_NODE_FN_PROTO_SIMPLE) {
        // data.lhs = optional param node, data.rhs = return type.
        // callconv_expr = .none (Ast.zig:1468).
        if (proto_data.lhs != 0) {
            param_nodes_buf[0] = proto_data.lhs;
            param_nodes = param_nodes_buf;
            params_len = 1;
        }
    } else if (proto_tag == AST_NODE_FN_PROTO_ONE) {
        // data.lhs = extra_data index → AstFnProtoOne.
        uint32_t extra_idx = proto_data.lhs;
        uint32_t param
            = tree->extra_data.arr[extra_idx]; // AstFnProtoOne.param
        if (param != 0) {
            param_nodes_buf[0] = param;
            param_nodes = param_nodes_buf;
            params_len = 1;
        }
        // AstFnProtoOne.callconv_expr at offset 4 (Ast.zig:4076).
        callconv_expr_node = tree->extra_data.arr[extra_idx + 4];
    } else if (proto_tag == AST_NODE_FN_PROTO_MULTI) {
        // data.lhs = extra_data index → SubRange{start, end}.
        // callconv_expr = .none (Ast.zig:1484).
        uint32_t extra_idx = proto_data.lhs;
        uint32_t range_start = tree->extra_data.arr[extra_idx];
        uint32_t range_end = tree->extra_data.arr[extra_idx + 1];
        param_nodes = tree->extra_data.arr + range_start;
        params_len = range_end - range_start;
    } else if (proto_tag == AST_NODE_FN_PROTO) {
        // data.lhs = extra_data index → AstFnProto{params_start, params_end,
        // ...}.
        uint32_t extra_idx = proto_data.lhs;
        uint32_t pstart = tree->extra_data.arr[extra_idx]; // params_start
        uint32_t pend = tree->extra_data.arr[extra_idx + 1]; // params_end
        param_nodes = tree->extra_data.arr + pstart;
        params_len = pend - pstart;
        // AstFnProto.callconv_expr at offset 5 (Ast.zig:4089).
        callconv_expr_node = tree->extra_data.arr[extra_idx + 5];
    }

    // decl_gz (called value_gz in caller, decl_gz in fnDeclInner)
    // (AstGen.zig:4194-4201).
    GenZir decl_gz;
    memset(&decl_gz, 0, sizeof(decl_gz));
    decl_gz.base.tag = SCOPE_GEN_ZIR;
    decl_gz.parent = scope;
    decl_gz.astgen = ag;
    decl_gz.decl_node_index = proto_node;
    decl_gz.decl_line = decl_line;
    decl_gz.is_comptime = true;
    decl_gz.instructions_top = ag->scratch_inst_len;
    decl_gz.break_block = UINT32_MAX;
    decl_gz.any_defer_node = UINT32_MAX;

    // --- Parameter iteration (AstGen.zig:4260-4363) ---
    // Walk params, creating param instructions and ScopeLocalVal entries.
    // We keep param scopes on the C stack (max 32 params like upstream).
    Scope* params_scope = &decl_gz.base;
    ScopeLocalVal param_scopes[32];
    uint32_t param_scope_count = 0;
    // Collect param instruction indices (AstGen.zig:4254, 4360).
    uint32_t param_insts[32];
    uint32_t param_insts_len = 0;
    // noalias_bits tracking (AstGen.zig:4259).
    uint32_t noalias_bits = 0;
    // Generic parameter/return type tracking (AstGen.zig:4257).
    bool any_param_used = false;
    // is_var_args detection (AstGen.zig:4261).
    bool is_var_args = false;

    // Parameter iteration using token-based iterator, mirroring upstream
    // FnProto.Iterator (Ast.zig:2680-2768, AstGen.zig:4260-4363).
    // The params array only contains type-expression params; anytype params
    // exist as tokens between/after the type-expression nodes.
    uint32_t lparen = fn_name_token + 1; // '(' token
    uint32_t iter_tok_i = lparen + 1; // first token after '('
    bool iter_tok_flag = true; // start in token-scanning mode
    uint32_t iter_param_i = 0;
    ResultLoc coerced_type_ri = { .tag = RL_COERCED_TY,
        .data = ZIR_REF_TYPE_TYPE,
        .src_node = 0,
        .ctx = RI_CTX_NONE };

    uint32_t param_type_i = 0; // index for noalias_bits (AstGen.zig:4262)
    while (true) {
        uint32_t name_token = 0;
        uint32_t comptime_noalias_token = 0;
        bool is_comptime_param = false;
        bool is_anytype = false;
        uint32_t param_type_node = 0;

        if (!iter_tok_flag) {
            // Return next param from params array.
            if (iter_param_i >= params_len)
                break;
            param_type_node = param_nodes[iter_param_i];
            // Scan backwards from type expression to find
            // name/comptime/noalias (Ast.zig:2698-2705).
            uint32_t tok_i = firstToken(tree, param_type_node);
            while (tok_i > 0) {
                tok_i--;
                uint32_t ttag = tree->tokens.tags[tok_i];
                if (ttag == TOKEN_COLON)
                    continue;
                if (ttag == TOKEN_IDENTIFIER) {
                    name_token = tok_i;
                    continue;
                }
                if (ttag == TOKEN_KEYWORD_COMPTIME
                    || ttag == TOKEN_KEYWORD_NOALIAS) {
                    comptime_noalias_token = tok_i;
                    continue;
                }
                break;
            }
            iter_param_i++;
            iter_tok_i = lastToken(tree, param_type_node) + 1;
            // Skip comma after param for anytype scanning.
            if (tree->tokens.tags[iter_tok_i] == TOKEN_COMMA)
                iter_tok_i++;
            iter_tok_flag = true;
        } else {
            // Token-scanning mode: look for anytype/ellipsis params
            // (Ast.zig:2721-2767).
            if (tree->tokens.tags[iter_tok_i] == TOKEN_COMMA)
                iter_tok_i++;
            if (tree->tokens.tags[iter_tok_i] == TOKEN_R_PAREN)
                break;
            // Skip doc comments.
            while (tree->tokens.tags[iter_tok_i] == TOKEN_DOC_COMMENT)
                iter_tok_i++;
            // Check for ellipsis3 (varargs) (AstGen.zig:4275-4281).
            if (tree->tokens.tags[iter_tok_i] == TOKEN_ELLIPSIS3) {
                is_var_args = true;
                break;
            }
            // Check for comptime/noalias prefix.
            if (tree->tokens.tags[iter_tok_i] == TOKEN_KEYWORD_COMPTIME
                || tree->tokens.tags[iter_tok_i] == TOKEN_KEYWORD_NOALIAS) {
                comptime_noalias_token = iter_tok_i;
                iter_tok_i++;
            }
            // Check for name: identifier followed by colon.
            if (tree->tokens.tags[iter_tok_i] == TOKEN_IDENTIFIER
                && tree->tokens.tags[iter_tok_i + 1] == TOKEN_COLON) {
                name_token = iter_tok_i;
                iter_tok_i += 2;
            }
            // Check for anytype keyword.
            if (tree->tokens.tags[iter_tok_i] == TOKEN_KEYWORD_ANYTYPE) {
                is_anytype = true;
                iter_tok_i++;
            } else {
                // Not an anytype param; switch to param-array mode.
                iter_tok_flag = false;
                continue;
            }
        }

        // Determine is_comptime and noalias from comptime_noalias token
        // (AstGen.zig:4265-4273).
        if (comptime_noalias_token != 0
            && tree->tokens.tags[comptime_noalias_token]
                == TOKEN_KEYWORD_NOALIAS) {
            // Track noalias_bits (AstGen.zig:4266-4269).
            if (param_type_i < 32)
                noalias_bits |= (1u << param_type_i);
        }
        if (comptime_noalias_token != 0
            && tree->tokens.tags[comptime_noalias_token]
                == TOKEN_KEYWORD_COMPTIME) {
            is_comptime_param = true;
        }

        // Determine param name string (AstGen.zig:4283-4321).
        // Must be resolved BEFORE type expression to match upstream string
        // table ordering.
        uint32_t param_name_str = 0; // NullTerminatedString.empty
        if (name_token != 0) {
            uint32_t name_start = tree->tokens.starts[name_token];
            char nch = tree->source[name_start];
            // Skip "_" params (AstGen.zig:4285-4286).
            if (nch == '_') {
                uint32_t next_start = tree->tokens.starts[name_token + 1];
                if (next_start == name_start + 1) {
                    // Single underscore: empty name.
                    param_name_str = 0;
                } else {
                    param_name_str = identAsString(ag, name_token);
                }
            } else {
                param_name_str = identAsString(ag, name_token);
            }
        }

        // Emit param instruction (AstGen.zig:4323-4345).
        uint32_t param_inst_ref;
        if (is_anytype) {
            // anytype parameter: emit param_anytype/param_anytype_comptime
            // (AstGen.zig:4323-4329).
            uint32_t anytype_name_token
                = name_token != 0 ? name_token : (iter_tok_i - 1);
            ZirInstTag anytype_tag = is_comptime_param
                ? ZIR_INST_PARAM_ANYTYPE_COMPTIME
                : ZIR_INST_PARAM_ANYTYPE;
            uint32_t anytype_inst = addStrTok(
                &decl_gz, anytype_tag, param_name_str, anytype_name_token);
            param_inst_ref = anytype_inst; // already a ref (toRef())
            if (param_insts_len < 32)
                param_insts[param_insts_len++]
                    = anytype_inst - ZIR_REF_START_INDEX; // toIndex()
        } else {
            // Type-expression parameter (AstGen.zig:4330-4344).
            any_param_used = false; // reset before evaluating type body
            GenZir param_gz = makeSubBlock(&decl_gz, params_scope);
            uint32_t param_type_ref = fullBodyExpr(
                &param_gz, params_scope, coerced_type_ri, param_type_node);

            if (ag->has_compile_errors)
                return;

            // The break_inline target is the param instruction we're about
            // to create (AstGen.zig:4336-4337).
            uint32_t param_inst_expected = ag->inst_len + 1;
            makeBreakInline(&param_gz, param_inst_expected, param_type_ref,
                (int32_t)param_type_node - (int32_t)param_gz.decl_node_index);
            bool param_type_is_generic = any_param_used;

            // Create param instruction (AstGen.zig:4341-4343).
            ZirInstTag param_tag
                = is_comptime_param ? ZIR_INST_PARAM_COMPTIME : ZIR_INST_PARAM;
            uint32_t name_tok_for_src = name_token != 0
                ? name_token
                : tree->nodes.main_tokens[param_type_node];
            uint32_t param_inst = addParam(&decl_gz, &param_gz, param_tag,
                name_tok_for_src, param_name_str, param_type_is_generic);
            (void)param_inst_expected;
            param_inst_ref = param_inst + ZIR_REF_START_INDEX;
            if (param_insts_len < 32)
                param_insts[param_insts_len++] = param_inst;
        }

        // Create ScopeLocalVal for this param (AstGen.zig:4349-4359).
        if (param_name_str != 0 && param_scope_count < 32) {
            ScopeLocalVal* lv = &param_scopes[param_scope_count++];
            lv->base.tag = SCOPE_LOCAL_VAL;
            lv->parent = params_scope;
            lv->gen_zir = &decl_gz;
            lv->inst = param_inst_ref;
            lv->token_src = name_token;
            lv->name = param_name_str;
            lv->is_used_or_discarded = &any_param_used;
            params_scope = &lv->base;
        }
        param_type_i++;
    }

    // --- Return type (AstGen.zig:4369-4383) ---
    any_param_used = false; // reset for return type generic detection
    GenZir ret_gz = makeSubBlock(&decl_gz, params_scope);
    uint32_t ret_ref = ZIR_REF_NONE;
    if (return_type_node != 0) {
        ret_ref = fullBodyExpr(
            &ret_gz, params_scope, coerced_type_ri, return_type_node);
        if (ag->has_compile_errors)
            return;
        // If ret_gz produced instructions, add break_inline
        // (AstGen.zig:4377-4381).
        if (gzInstructionsLen(&ret_gz) > 0) {
            // break_inline targets the func instruction (which doesn't
            // exist yet). We use 0 as placeholder and patch later.
            makeBreakInline(&ret_gz, 0, ret_ref, AST_NODE_OFFSET_NONE);
        }
    }
    // Fetch ref entries for params used in return type (AstGen.zig:4384).
    uint32_t ret_param_refs[32];
    uint32_t ret_param_refs_len = fetchRemoveRefEntries(
        ag, param_insts, param_insts_len, ret_param_refs, 32);
    bool ret_ty_is_generic = any_param_used;
    // Map void_type → .none (AstGen.zig:12054).
    if (ret_ref == ZIR_REF_VOID_TYPE)
        ret_ref = ZIR_REF_NONE;

    uint32_t ret_body_len = gzInstructionsLen(&ret_gz);
    // Copy ret_body before unstacking: body_gz reuses the same scratch area.
    uint32_t* ret_body = NULL;
    if (ret_body_len > 0) {
        ret_body = malloc(ret_body_len * sizeof(uint32_t));
        if (!ret_body)
            abort();
        memcpy(ret_body, gzInstructionsSlice(&ret_gz),
            ret_body_len * sizeof(uint32_t));
    }
    gzUnstack(&ret_gz);

    // Restore source cursor (AstGen.zig:4387-4388).
    ag->source_offset = saved_source_offset;
    ag->source_line = saved_source_line;
    ag->source_column = saved_source_column;

    // --- Calling convention (AstGen.zig:4390-4413) ---
    // Note: cc_gz uses `scope` (= &decl_gz.base), not params_scope.
    GenZir cc_gz = makeSubBlock(&decl_gz, &decl_gz.base);
    uint32_t cc_ref = ZIR_REF_NONE;
    if (callconv_expr_node != 0) {
        // Explicit callconv(expr) (AstGen.zig:4393-4405).
        uint32_t cc_ty = addBuiltinValue(
            &cc_gz, callconv_expr_node, ZIR_BUILTIN_VALUE_CALLING_CONVENTION);
        ResultLoc cc_ri = { .tag = RL_COERCED_TY,
            .data = cc_ty,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        cc_ref = exprRl(&cc_gz, &decl_gz.base, cc_ri, callconv_expr_node);
        if (ag->has_compile_errors) {
            free(ret_body);
            return;
        }
        if (gzInstructionsLen(&cc_gz) > 0) {
            // break_inline targets the func instruction (patched later).
            makeBreakInline(&cc_gz, 0, cc_ref, AST_NODE_OFFSET_NONE);
        }
    } else if (has_inline_keyword) {
        // inline keyword → calling_convention_inline
        // (AstGen.zig:4406-4409).
        cc_ref = addBuiltinValue(
            &cc_gz, node, ZIR_BUILTIN_VALUE_CALLING_CONVENTION_INLINE);
        makeBreakInline(&cc_gz, 0, cc_ref, AST_NODE_OFFSET_NONE);
    }

    uint32_t cc_body_len = gzInstructionsLen(&cc_gz);
    uint32_t* cc_body = NULL;
    if (cc_body_len > 0) {
        cc_body = malloc(cc_body_len * sizeof(uint32_t));
        if (!cc_body)
            abort();
        memcpy(cc_body, gzInstructionsSlice(&cc_gz),
            cc_body_len * sizeof(uint32_t));
    }
    gzUnstack(&cc_gz);

    // --- Body handling ---
    // For fn_proto* (no body): extern function, emit type only
    // (AstGen.zig:4136-4164).
    // For fn_decl (has body): emit function value (AstGen.zig:4197-4201).
    uint32_t func_ref;
    if (body_node == 0) {
        // fn_proto without body: extern function type.
        // Upstream emits fnProtoExprInner; we SET_ERROR for now as
        // fnProtoExprInner is not yet ported.
        // TODO: implement fnProtoExprInner for extern fn support.
        SET_ERROR(ag);
        free(ret_body);
        free(cc_body);
        gzUnstack(&decl_gz);
        ag->within_fn = prev_within_fn;
        return;
    }

    // --- Body (AstGen.zig:4415-4424) ---
    GenZir body_gz;
    memset(&body_gz, 0, sizeof(body_gz));
    body_gz.base.tag = SCOPE_GEN_ZIR;
    body_gz.parent = params_scope;
    body_gz.astgen = ag;
    body_gz.decl_node_index = proto_node;
    body_gz.decl_line = decl_line;
    body_gz.is_comptime = false;
    body_gz.instructions_top = ag->scratch_inst_len;
    body_gz.any_defer_node = UINT32_MAX;

    // Set fn_block, fn_ret_ty, fn_var_args for the body
    // (AstGen.zig:4442-4459).
    void* prev_fn_block = ag->fn_block;
    setFnBlock(ag, &body_gz);
    uint32_t prev_fn_ret_ty = ag->fn_ret_ty;
    bool prev_fn_var_args = ag->fn_var_args;
    ag->fn_var_args = is_var_args;
    if (is_inferred_error || ret_ref == ZIR_REF_NONE) {
        // Non-void non-trivial return type: emit ret_type instruction.
        if (ret_body_len > 0 || is_inferred_error) {
            ZirInstData rtdata;
            memset(&rtdata, 0, sizeof(rtdata));
            rtdata.node = (int32_t)node - (int32_t)body_gz.decl_node_index;
            ag->fn_ret_ty
                = addInstruction(&body_gz, ZIR_INST_RET_TYPE, rtdata);
        } else {
            ag->fn_ret_ty = ret_ref; // void
        }
    } else {
        // ret_ref is a simple ref (not void, not inferred error).
        // Still need ret_type instruction if it resolved to an inst.
        if (ret_ref >= ZIR_REF_START_INDEX) {
            ZirInstData rtdata;
            memset(&rtdata, 0, sizeof(rtdata));
            rtdata.node = (int32_t)node - (int32_t)body_gz.decl_node_index;
            ag->fn_ret_ty
                = addInstruction(&body_gz, ZIR_INST_RET_TYPE, rtdata);
        } else {
            ag->fn_ret_ty = ret_ref;
        }
    }

    // Process function body (AstGen.zig:4461-4465).
    advanceSourceCursorToNode(ag, body_node);
    uint32_t lbrace_line = ag->source_line - decl_line;
    uint32_t lbrace_column = ag->source_column;

    fullBodyExpr(&body_gz, &body_gz.base, RL_NONE_VAL, body_node);

    ag->within_fn = prev_within_fn;
    ag->fn_block = prev_fn_block;
    ag->fn_ret_ty = prev_fn_ret_ty;
    ag->fn_var_args = prev_fn_var_args;

    if (ag->has_compile_errors) {
        free(ret_body);
        free(cc_body);
        return;
    }

    // Add implicit return at end of function body
    // (AstGen.zig:4465-4871).
    if (!endsWithNoReturn(&body_gz)) {
        ZirInstData rdata;
        rdata.un_node.operand = ZIR_REF_NONE;
        rdata.un_node.src_node
            = (int32_t)node - (int32_t)body_gz.decl_node_index;
        addInstruction(
            &body_gz, ZIR_INST_RESTORE_ERR_RET_INDEX_UNCONDITIONAL, rdata);

        uint32_t body_last_tok = lastToken(tree, body_node);
        ZirInstData rdata2;
        rdata2.un_tok.operand = ZIR_REF_VOID_VALUE;
        rdata2.un_tok.src_tok = tokenIndexToRelative(&body_gz, body_last_tok);
        addInstruction(&body_gz, ZIR_INST_RET_IMPLICIT, rdata2);
    }

    // Read body before unstacking (AstGen.zig:12215-12218).
    const uint32_t* fn_body = gzInstructionsSlice(&body_gz);
    uint32_t fn_body_len = gzInstructionsLen(&body_gz);
    gzUnstack(&body_gz);

    // Create func/func_fancy instruction (AstGen.zig:4476-4494,
    // 12112-12173).
    bool need_fancy = cc_ref != ZIR_REF_NONE || is_var_args
        || noalias_bits != 0 || is_noinline;
    if (need_fancy) {
        func_ref = addFuncFancy(&decl_gz, node, body_node, decl_inst, ret_ref,
            ret_body, ret_body_len, cc_ref, cc_body, cc_body_len, fn_body,
            fn_body_len, param_insts, param_insts_len, lbrace_line,
            lbrace_column, is_var_args, is_inferred_error, is_noinline,
            noalias_bits, ret_ty_is_generic, ret_param_refs,
            ret_param_refs_len);
    } else {
        func_ref = addFunc(&decl_gz, node, body_node, decl_inst, ret_ref,
            ret_body, ret_body_len, fn_body, fn_body_len, param_insts,
            param_insts_len, lbrace_line, lbrace_column, is_inferred_error,
            ret_ty_is_generic, ret_param_refs, ret_param_refs_len);
    }

    // Patch ret_body break_inline to point to func instruction
    // (AstGen.zig:12199-12202).
    if (ret_body_len > 0) {
        uint32_t break_inst = ret_body[ret_body_len - 1];
        uint32_t break_payload
            = ag->inst_datas[break_inst].break_data.payload_index;
        ag->extra[break_payload + 1] = func_ref - ZIR_REF_START_INDEX;
    }
    // Patch cc_body break_inline to point to func instruction
    // (AstGen.zig:12146-12148).
    if (cc_body_len > 0) {
        uint32_t break_inst = cc_body[cc_body_len - 1];
        uint32_t break_payload
            = ag->inst_datas[break_inst].break_data.payload_index;
        ag->extra[break_payload + 1] = func_ref - ZIR_REF_START_INDEX;
    }
    free(ret_body);
    free(cc_body);

    // break_inline returning func to declaration (AstGen.zig:4495).
    // nodeIndexToRelative(decl_node) = node - decl_gz.decl_node_index.
    makeBreakInline(
        &decl_gz, decl_inst, func_ref, (int32_t)node - (int32_t)proto_node);

    // setDeclaration (AstGen.zig:4208-4225).
    // Linkage: export > normal (AstGen.zig:4217).
    DeclFlagsId decl_id;
    if (is_export)
        decl_id = is_pub ? DECL_ID_PUB_EXPORT_CONST : DECL_ID_EXPORT_CONST;
    else
        decl_id = is_pub ? DECL_ID_PUB_CONST_SIMPLE : DECL_ID_CONST_SIMPLE;
    uint32_t name_str = identAsString(ag, fn_name_token);
    setDeclaration(ag, decl_inst,
        (SetDeclArgs) { .src_line = decl_line,
            .src_column = decl_column,
            .id = decl_id,
            .name = name_str,
            .lib_name = UINT32_MAX,
            .value_body = gzInstructionsSlice(&decl_gz),
            .value_body_len = gzInstructionsLen(&decl_gz) });
    gzUnstack(&decl_gz);

    (void)gz;
}

// --- comptimeDecl (AstGen.zig:4645) ---

static void comptimeDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
    uint32_t* wip_decl_insts, uint32_t* decl_idx, uint32_t node) {
    // makeDeclaration before advanceSourceCursorToNode (AstGen.zig:4663-4665).
    uint32_t decl_inst = makeDeclaration(ag, node);
    wip_decl_insts[*decl_idx] = decl_inst;
    (*decl_idx)++;

    advanceSourceCursorToNode(ag, node);

    uint32_t decl_line = ag->source_line;
    uint32_t decl_column = ag->source_column;

    // Value sub-block (AstGen.zig:4675-4686).
    GenZir value_gz;
    memset(&value_gz, 0, sizeof(value_gz));
    value_gz.base.tag = SCOPE_GEN_ZIR;
    value_gz.parent = scope;
    value_gz.astgen = ag;
    value_gz.decl_node_index = node;
    value_gz.decl_line = decl_line;
    value_gz.is_comptime = true;
    value_gz.instructions_top = ag->scratch_inst_len;
    value_gz.any_defer_node = UINT32_MAX;

    // For comptime {}: body is empty block → no instructions generated.
    // comptime_gz.isEmpty() == true → addBreak(.break_inline, decl_inst,
    // .void_value) (AstGen.zig:4685-4686)
    makeBreakInline(
        &value_gz, decl_inst, ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);

    setDeclaration(ag, decl_inst,
        (SetDeclArgs) { .src_line = decl_line,
            .src_column = decl_column,
            .id = DECL_ID_COMPTIME,
            .name = 0,
            .lib_name = UINT32_MAX,
            .value_body = gzInstructionsSlice(&value_gz),
            .value_body_len = gzInstructionsLen(&value_gz) });
    gzUnstack(&value_gz);

    (void)gz;
}

// --- globalVarDecl (AstGen.zig:4498) ---

// Extract VarDecl fields from an AST node (Ast.zig:1326-1380).
typedef struct {
    uint32_t mut_token;
    uint32_t type_node; // 0 = none
    uint32_t align_node; // 0 = none
    uint32_t addrspace_node; // 0 = none
    uint32_t section_node; // 0 = none
    uint32_t init_node; // UINT32_MAX = none
    bool is_pub;
    bool is_extern;
    bool is_export;
    bool is_mutable;
    bool is_threadlocal;
    uint32_t lib_name_token; // UINT32_MAX = none
} VarDeclInfo;

static VarDeclInfo extractVarDecl(const Ast* tree, uint32_t node) {
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];
    uint32_t mut_token = tree->nodes.main_tokens[node];
    VarDeclInfo info;
    memset(&info, 0, sizeof(info));
    info.mut_token = mut_token;
    info.init_node = UINT32_MAX;
    info.lib_name_token = UINT32_MAX;

    switch (tag) {
    case AST_NODE_SIMPLE_VAR_DECL:
        // lhs = type_node (optional), rhs = init_node (optional)
        info.type_node = nd.lhs;
        info.init_node = nd.rhs;
        break;
    case AST_NODE_ALIGNED_VAR_DECL:
        // lhs = align_node, rhs = init_node (optional)
        info.align_node = nd.lhs;
        info.init_node = nd.rhs;
        break;
    case AST_NODE_GLOBAL_VAR_DECL: {
        // lhs = extra_data index, rhs = init_node (optional)
        uint32_t ei = nd.lhs;
        info.type_node = tree->extra_data.arr[ei + 0];
        info.align_node = tree->extra_data.arr[ei + 1];
        info.addrspace_node = tree->extra_data.arr[ei + 2];
        info.section_node = tree->extra_data.arr[ei + 3];
        info.init_node = nd.rhs;
        break;
    }
    case AST_NODE_LOCAL_VAR_DECL: {
        // lhs = extra_data index, rhs = init_node (optional)
        uint32_t ei = nd.lhs;
        info.type_node = tree->extra_data.arr[ei + 0];
        info.align_node = tree->extra_data.arr[ei + 1];
        info.init_node = nd.rhs;
        break;
    }
    default:
        break;
    }

    // Scan backwards from mut_token to find modifiers (Ast.zig:2003-2025).
    info.is_mutable = (tree->tokens.tags[mut_token] == TOKEN_KEYWORD_VAR);
    for (uint32_t i = mut_token; i > 0;) {
        i--;
        TokenizerTag ttag = tree->tokens.tags[i];
        if (ttag == TOKEN_KEYWORD_EXTERN)
            info.is_extern = true;
        else if (ttag == TOKEN_KEYWORD_EXPORT)
            info.is_export = true;
        else if (ttag == TOKEN_KEYWORD_PUB)
            info.is_pub = true;
        else if (ttag == TOKEN_KEYWORD_THREADLOCAL)
            info.is_threadlocal = true;
        else if (ttag == TOKEN_STRING_LITERAL)
            info.lib_name_token = i;
        else
            break;
    }
    return info;
}

// Compute DeclFlagsId from VarDecl properties (AstGen.zig:13916-13972).
static DeclFlagsId computeVarDeclId(bool is_mutable, bool is_pub,
    bool is_extern, bool is_export, bool is_threadlocal, bool has_type_body,
    bool has_special_body, bool has_lib_name) {
    if (!is_mutable) {
        // const
        if (is_extern) {
            if (is_pub) {
                if (has_lib_name || has_special_body)
                    return DECL_ID_PUB_EXTERN_CONST;
                return DECL_ID_PUB_EXTERN_CONST_SIMPLE;
            }
            if (has_lib_name || has_special_body)
                return DECL_ID_EXTERN_CONST;
            return DECL_ID_EXTERN_CONST_SIMPLE;
        }
        if (is_export)
            return is_pub ? DECL_ID_PUB_EXPORT_CONST : DECL_ID_EXPORT_CONST;
        if (is_pub) {
            if (has_special_body)
                return DECL_ID_PUB_CONST;
            if (has_type_body)
                return DECL_ID_PUB_CONST_TYPED;
            return DECL_ID_PUB_CONST_SIMPLE;
        }
        if (has_special_body)
            return DECL_ID_CONST;
        if (has_type_body)
            return DECL_ID_CONST_TYPED;
        return DECL_ID_CONST_SIMPLE;
    }
    // var
    if (is_extern) {
        if (is_pub) {
            if (is_threadlocal)
                return DECL_ID_PUB_EXTERN_VAR_THREADLOCAL;
            return DECL_ID_PUB_EXTERN_VAR;
        }
        if (is_threadlocal)
            return DECL_ID_EXTERN_VAR_THREADLOCAL;
        return DECL_ID_EXTERN_VAR;
    }
    if (is_export) {
        if (is_pub) {
            if (is_threadlocal)
                return DECL_ID_PUB_EXPORT_VAR_THREADLOCAL;
            return DECL_ID_PUB_EXPORT_VAR;
        }
        if (is_threadlocal)
            return DECL_ID_EXPORT_VAR_THREADLOCAL;
        return DECL_ID_EXPORT_VAR;
    }
    if (is_pub) {
        if (is_threadlocal)
            return DECL_ID_PUB_VAR_THREADLOCAL;
        if (has_special_body || has_type_body)
            return DECL_ID_PUB_VAR;
        return DECL_ID_PUB_VAR_SIMPLE;
    }
    if (is_threadlocal)
        return DECL_ID_VAR_THREADLOCAL;
    if (has_special_body || has_type_body)
        return DECL_ID_VAR;
    return DECL_ID_VAR_SIMPLE;
}

// Mirrors nameStratExpr (AstGen.zig:1160-1199).
// Checks if node is a container decl or @Type builtin; if so, dispatches
// with the given name_strategy. Returns true if handled (result stored in
// *out_ref), false if caller should fall back to expr().
static bool nameStratExpr(GenZir* gz, Scope* scope, ResultLoc rl,
    uint32_t node, uint8_t name_strategy, uint32_t* out_ref) {
    const AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    (void)rl; // Used by builtinReify (not yet implemented).

    switch (tag) {
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING:
        *out_ref = containerDecl(gz, scope, node, name_strategy);
        return true;
    // @Type builtin: upstream calls builtinReify (AstGen.zig:1186-1196).
    // Not yet implemented; fall through to expr().
    default:
        return false;
    }
}

static void globalVarDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
    uint32_t* wip_decl_insts, uint32_t* decl_idx, uint32_t node) {
    const Ast* tree = ag->tree;
    VarDeclInfo vd = extractVarDecl(tree, node);
    uint32_t name_token = vd.mut_token + 1;

    // "threadlocal variable cannot be constant" (AstGen.zig:4526-4528).
    if (vd.is_threadlocal && !vd.is_mutable) {
        SET_ERROR(ag);
        return;
    }

    // lib_name validation (AstGen.zig:4531-4540).
    uint32_t lib_name = UINT32_MAX;
    if (vd.lib_name_token != UINT32_MAX) {
        uint32_t li, ll;
        strLitAsString(ag, vd.lib_name_token, &li, &ll);
        // "library name cannot contain null bytes" (AstGen.zig:4534-4535).
        if (memchr(ag->string_bytes + li, 0, ll) != NULL) {
            SET_ERROR(ag);
            return;
        }
        // "library name cannot be empty" (AstGen.zig:4536-4537).
        if (ll == 0) {
            SET_ERROR(ag);
            return;
        }
        lib_name = li;
    }

    // advanceSourceCursorToNode before makeDeclaration (AstGen.zig:4542-4546).
    advanceSourceCursorToNode(ag, node);
    uint32_t decl_column = ag->source_column;

    uint32_t decl_inst = makeDeclaration(ag, node);
    wip_decl_insts[*decl_idx] = decl_inst;
    (*decl_idx)++;

    // "extern variables have no initializers" (AstGen.zig:4549-4556).
    if (vd.init_node != UINT32_MAX && vd.init_node != 0) {
        if (vd.is_extern) {
            SET_ERROR(ag);
            return;
        }
    } else {
        // "variables must be initialized" (AstGen.zig:4557-4561).
        if (!vd.is_extern) {
            SET_ERROR(ag);
            return;
        }
    }

    // "unable to infer variable type" (AstGen.zig:4563-4565).
    if (vd.is_extern && vd.type_node == 0) {
        SET_ERROR(ag);
        return;
    }

    // Set up type sub-block (AstGen.zig:4574-4582).
    GenZir type_gz;
    memset(&type_gz, 0, sizeof(type_gz));
    type_gz.base.tag = SCOPE_GEN_ZIR;
    type_gz.parent = scope;
    type_gz.astgen = ag;
    type_gz.decl_node_index = node;
    type_gz.instructions_top = ag->scratch_inst_len;
    type_gz.decl_line = ag->source_line;
    type_gz.is_comptime = true;
    type_gz.any_defer_node = UINT32_MAX;

    if (vd.type_node != 0) {
        uint32_t type_inst = typeExpr(&type_gz, &type_gz.base, vd.type_node);
        makeBreakInline(&type_gz, decl_inst, type_inst, 0);
    }

    // Record type_gz boundary for slicing.
    uint32_t type_top = ag->scratch_inst_len;

    // Align sub-block (AstGen.zig:4585-4591).
    GenZir align_gz;
    memset(&align_gz, 0, sizeof(align_gz));
    align_gz.base.tag = SCOPE_GEN_ZIR;
    align_gz.parent = scope;
    align_gz.astgen = ag;
    align_gz.decl_node_index = node;
    align_gz.instructions_top = type_top;
    align_gz.decl_line = ag->source_line;
    align_gz.is_comptime = true;
    align_gz.any_defer_node = UINT32_MAX;

    if (vd.align_node != 0) {
        // coerced_align_ri = { .rl = .{ .coerced_ty = .u29_type } }
        // (AstGen.zig:389, 4589).
        ResultLoc align_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_U29_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t align_inst
            = exprRl(&align_gz, &align_gz.base, align_rl, vd.align_node);
        makeBreakInline(&align_gz, decl_inst, align_inst, 0);
    }

    uint32_t align_top = ag->scratch_inst_len;

    // Linksection sub-block (AstGen.zig:4593-4599).
    GenZir linksection_gz;
    memset(&linksection_gz, 0, sizeof(linksection_gz));
    linksection_gz.base.tag = SCOPE_GEN_ZIR;
    linksection_gz.parent = scope;
    linksection_gz.astgen = ag;
    linksection_gz.decl_node_index = node;
    linksection_gz.instructions_top = align_top;
    linksection_gz.decl_line = ag->source_line;
    linksection_gz.is_comptime = true;
    linksection_gz.any_defer_node = UINT32_MAX;

    if (vd.section_node != 0) {
        // coerced_linksection_ri = { .rl = .{ .coerced_ty =
        //     .slice_const_u8_type } } (AstGen.zig:390, 4597).
        ResultLoc ls_rl = { .tag = RL_COERCED_TY,
            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t ls_inst = exprRl(
            &linksection_gz, &linksection_gz.base, ls_rl, vd.section_node);
        makeBreakInline(&linksection_gz, decl_inst, ls_inst, 0);
    }

    uint32_t linksection_top = ag->scratch_inst_len;

    // Addrspace sub-block (AstGen.zig:4601-4608).
    GenZir addrspace_gz;
    memset(&addrspace_gz, 0, sizeof(addrspace_gz));
    addrspace_gz.base.tag = SCOPE_GEN_ZIR;
    addrspace_gz.parent = scope;
    addrspace_gz.astgen = ag;
    addrspace_gz.decl_node_index = node;
    addrspace_gz.instructions_top = linksection_top;
    addrspace_gz.decl_line = ag->source_line;
    addrspace_gz.is_comptime = true;
    addrspace_gz.any_defer_node = UINT32_MAX;

    if (vd.addrspace_node != 0) {
        // Upstream: addBuiltinValue(addrspace_node, .address_space) then
        // coerced_ty with that result (AstGen.zig:4605-4606).
        uint32_t addrspace_ty = addBuiltinValue(
            &addrspace_gz, vd.addrspace_node, ZIR_BUILTIN_VALUE_ADDRESS_SPACE);
        ResultLoc as_rl = { .tag = RL_COERCED_TY,
            .data = addrspace_ty,
            .src_node = 0,
            .ctx = RI_CTX_NONE };
        uint32_t as_inst = exprRl(
            &addrspace_gz, &addrspace_gz.base, as_rl, vd.addrspace_node);
        makeBreakInline(&addrspace_gz, decl_inst, as_inst, 0);
    }

    uint32_t addrspace_top = ag->scratch_inst_len;

    // Value sub-block (AstGen.zig:4610-4621).
    GenZir value_gz;
    memset(&value_gz, 0, sizeof(value_gz));
    value_gz.base.tag = SCOPE_GEN_ZIR;
    value_gz.parent = scope;
    value_gz.astgen = ag;
    value_gz.decl_node_index = node;
    value_gz.instructions_top = addrspace_top;
    value_gz.decl_line = ag->source_line;
    value_gz.is_comptime = true;
    value_gz.any_defer_node = UINT32_MAX;

    if (vd.init_node != UINT32_MAX && vd.init_node != 0) {
        // Upstream: coerced_ty = decl_inst.toRef() when type_node present
        // (AstGen.zig:4614-4616).
        ResultLoc init_rl;
        memset(&init_rl, 0, sizeof(init_rl));
        if (vd.type_node != 0) {
            init_rl.tag = RL_COERCED_TY;
            init_rl.data = decl_inst + ZIR_REF_START_INDEX;
        } else {
            init_rl.tag = RL_NONE;
        }
        // nameStratExpr: check if init is container decl (AstGen.zig:4617).
        uint32_t init_ref;
        if (!nameStratExpr(&value_gz, &value_gz.base, init_rl, vd.init_node,
                0 /* parent */, &init_ref)) {
            init_ref
                = exprRl(&value_gz, &value_gz.base, init_rl, vd.init_node);
        }
        makeBreakInline(&value_gz, decl_inst, init_ref, 0);
    }

    // Compute body slices (instructionsSliceUpto).
    const uint32_t* type_body
        = ag->scratch_instructions + type_gz.instructions_top;
    uint32_t type_body_len = type_top - type_gz.instructions_top;
    const uint32_t* align_body
        = ag->scratch_instructions + align_gz.instructions_top;
    uint32_t align_body_len = align_top - align_gz.instructions_top;
    const uint32_t* ls_body
        = ag->scratch_instructions + linksection_gz.instructions_top;
    uint32_t ls_body_len = linksection_top - linksection_gz.instructions_top;
    const uint32_t* as_body
        = ag->scratch_instructions + addrspace_gz.instructions_top;
    uint32_t as_body_len = addrspace_top - addrspace_gz.instructions_top;
    const uint32_t* val_body = gzInstructionsSlice(&value_gz);
    uint32_t val_body_len = gzInstructionsLen(&value_gz);

    bool has_type_body = (type_body_len > 0);
    bool has_special_body
        = (align_body_len > 0 || ls_body_len > 0 || as_body_len > 0);
    bool has_lib_name = (vd.lib_name_token != UINT32_MAX);

    uint32_t name_str = identAsString(ag, name_token);

    DeclFlagsId decl_id = computeVarDeclId(vd.is_mutable, vd.is_pub,
        vd.is_extern, vd.is_export, vd.is_threadlocal, has_type_body,
        has_special_body, has_lib_name);

    setDeclaration(ag, decl_inst,
        (SetDeclArgs) { .src_line = type_gz.decl_line,
            .src_column = decl_column,
            .id = decl_id,
            .name = name_str,
            .lib_name = lib_name,
            .type_body = type_body,
            .type_body_len = type_body_len,
            .align_body = align_body,
            .align_body_len = align_body_len,
            .linksection_body = ls_body,
            .linksection_body_len = ls_body_len,
            .addrspace_body = as_body,
            .addrspace_body_len = as_body_len,
            .value_body = val_body,
            .value_body_len = val_body_len });

    gzUnstack(&value_gz);

    (void)gz;
}

// --- nodeImpliesMoreThanOnePossibleValue (AstGen.zig:10548) ---
// Check if an identifier is a primitive type with more than one value.
static bool identImpliesMoreThanOnePossibleValue(
    const Ast* tree, uint32_t main_token) {
    uint32_t start = tree->tokens.starts[main_token];
    const char* src = tree->source + start;
    // Match known primitive types that have more than one possible value.
    // (AstGen.zig:10729-10766)
    if (src[0] == 'u' || src[0] == 'i') {
        // u8, u16, u32, u64, u128, u1, u29, usize, i8, i16, i32, i64, i128,
        // isize
        char c1 = src[1];
        if (c1 >= '0' && c1 <= '9')
            return true;
        if (c1 == 's') // usize, isize
            return (src[2] == 'i' && src[3] == 'z' && src[4] == 'e');
    }
    if (src[0] == 'f') {
        // f16, f32, f64, f80, f128
        char c1 = src[1];
        if (c1 >= '0' && c1 <= '9')
            return true;
    }
    if (src[0] == 'b' && src[1] == 'o' && src[2] == 'o' && src[3] == 'l'
        && !(src[4] >= 'a' && src[4] <= 'z')
        && !(src[4] >= 'A' && src[4] <= 'Z')
        && !(src[4] >= '0' && src[4] <= '9') && src[4] != '_')
        return true;
    if (src[0] == 'c' && src[1] == '_')
        return true; // c_int, c_long, etc.
    if (src[0] == 'a' && src[1] == 'n' && src[2] == 'y') {
        // anyerror, anyframe, anyopaque
        return true;
    }
    if (src[0] == 'c' && src[1] == 'o' && src[2] == 'm' && src[3] == 'p'
        && src[4] == 't' && src[5] == 'i' && src[6] == 'm' && src[7] == 'e')
        return true; // comptime_float, comptime_int
    if (src[0] == 't' && src[1] == 'y' && src[2] == 'p' && src[3] == 'e'
        && !(src[4] >= 'a' && src[4] <= 'z')
        && !(src[4] >= 'A' && src[4] <= 'Z')
        && !(src[4] >= '0' && src[4] <= '9') && src[4] != '_')
        return true;
    return false;
}

static bool nodeImpliesMoreThanOnePossibleValue(
    const Ast* tree, uint32_t node) {
    uint32_t cur = node;
    while (1) {
        AstNodeTag tag = tree->nodes.tags[cur];
        switch (tag) {
        // Pointer/optional/array/anyframe types → true
        // (AstGen.zig:10718-10725)
        case AST_NODE_PTR_TYPE_ALIGNED:
        case AST_NODE_PTR_TYPE_SENTINEL:
        case AST_NODE_PTR_TYPE:
        case AST_NODE_PTR_TYPE_BIT_RANGE:
        case AST_NODE_OPTIONAL_TYPE:
        case AST_NODE_ANYFRAME_TYPE:
        case AST_NODE_ARRAY_TYPE_SENTINEL:
            return true;
        // Forward to LHS: try, comptime, nosuspend
        // (AstGen.zig:10710-10713)
        case AST_NODE_TRY:
        case AST_NODE_COMPTIME:
        case AST_NODE_NOSUSPEND:
            cur = tree->nodes.datas[cur].lhs;
            continue;
        // Forward to LHS: grouped_expression, unwrap_optional
        // (AstGen.zig:10714-10716)
        case AST_NODE_GROUPED_EXPRESSION:
        case AST_NODE_UNWRAP_OPTIONAL:
            cur = tree->nodes.datas[cur].lhs;
            continue;
        // Identifier: check primitives (AstGen.zig:10727-10780)
        case AST_NODE_IDENTIFIER:
            return identImpliesMoreThanOnePossibleValue(
                tree, tree->nodes.main_tokens[cur]);
        default:
            return false;
        }
    }
}

// --- nodeImpliesComptimeOnly (AstGen.zig:10787) ---

static bool identImpliesComptimeOnly(const Ast* tree, uint32_t main_token) {
    uint32_t start = tree->tokens.starts[main_token];
    const char* src = tree->source + start;
    // Only comptime_float, comptime_int, type → true
    // (AstGen.zig:11010-11013)
    if (src[0] == 'c' && src[1] == 'o' && src[2] == 'm' && src[3] == 'p'
        && src[4] == 't' && src[5] == 'i' && src[6] == 'm' && src[7] == 'e')
        return true; // comptime_float, comptime_int
    if (src[0] == 't' && src[1] == 'y' && src[2] == 'p' && src[3] == 'e'
        && !(src[4] >= 'a' && src[4] <= 'z')
        && !(src[4] >= 'A' && src[4] <= 'Z')
        && !(src[4] >= '0' && src[4] <= '9') && src[4] != '_')
        return true;
    return false;
}

static bool nodeImpliesComptimeOnly(const Ast* tree, uint32_t node) {
    uint32_t cur = node;
    while (1) {
        AstNodeTag tag = tree->nodes.tags[cur];
        switch (tag) {
        // Function prototypes → true (AstGen.zig:10950-10955)
        case AST_NODE_FN_PROTO_SIMPLE:
        case AST_NODE_FN_PROTO_MULTI:
        case AST_NODE_FN_PROTO_ONE:
        case AST_NODE_FN_PROTO:
            return true;
        // Forward to LHS: try, comptime, nosuspend
        case AST_NODE_TRY:
        case AST_NODE_COMPTIME:
        case AST_NODE_NOSUSPEND:
            cur = tree->nodes.datas[cur].lhs;
            continue;
        case AST_NODE_GROUPED_EXPRESSION:
        case AST_NODE_UNWRAP_OPTIONAL:
            cur = tree->nodes.datas[cur].lhs;
            continue;
        // Identifier: check primitives
        case AST_NODE_IDENTIFIER:
            return identImpliesComptimeOnly(
                tree, tree->nodes.main_tokens[cur]);
        default:
            return false;
        }
    }
}

// --- WipMembers (AstGen.zig:3989) ---
// Tracks decl indices, field bit-flags, and per-field data during container
// processing. All data lives in a single malloc'd array laid out as:
//   [decls (decl_count)] [field_bits (ceil)] [fields (up to field_count*max)]
// Bodies are tracked separately in a dynamic array.

typedef struct {
    uint32_t* payload; // malloc'd array
    uint32_t payload_top; // always 0 (start of decls region)
    uint32_t field_bits_start;
    uint32_t fields_start;
    uint32_t fields_end;
    uint32_t decl_index;
    uint32_t field_index;
    // Bodies scratch: dynamically grown array for field type/align/init
    // bodies.
    uint32_t* bodies;
    uint32_t bodies_len;
    uint32_t bodies_cap;
} WipMembers;

// Parameterized init (AstGen.zig:3989 WipMembers.init).
static WipMembers wipMembersInitEx(uint32_t decl_count, uint32_t field_count,
    uint32_t bits_per_field, uint32_t max_field_size) {
    uint32_t fields_per_u32 = bits_per_field > 0 ? 32 / bits_per_field : 0;
    uint32_t field_bits_start = decl_count;
    uint32_t bit_words = (field_count > 0 && fields_per_u32 > 0)
        ? (field_count + fields_per_u32 - 1) / fields_per_u32
        : 0;
    uint32_t fields_start = field_bits_start + bit_words;
    uint32_t payload_end = fields_start + field_count * max_field_size;
    uint32_t alloc_size = payload_end > 0 ? payload_end : 1;
    uint32_t* payload = calloc(alloc_size, sizeof(uint32_t));
    if (!payload)
        exit(1);
    WipMembers wm;
    memset(&wm, 0, sizeof(wm));
    wm.payload = payload;
    wm.payload_top = 0;
    wm.field_bits_start = field_bits_start;
    wm.fields_start = fields_start;
    wm.fields_end = fields_start;
    wm.decl_index = 0;
    wm.field_index = 0;
    wm.bodies = NULL;
    wm.bodies_len = 0;
    wm.bodies_cap = 0;
    return wm;
}

static WipMembers wipMembersInit(uint32_t decl_count, uint32_t field_count) {
    // bits_per_field = 4, max_field_size = 5
    return wipMembersInitEx(decl_count, field_count, 4, 5);
}

static void wipMembersDeinit(WipMembers* wm) {
    free(wm->payload);
    free(wm->bodies);
}

static void wipMembersNextDecl(WipMembers* wm, uint32_t decl_inst) {
    wm->payload[wm->payload_top + wm->decl_index] = decl_inst;
    wm->decl_index++;
}

// bits_per_field = 4: bits[0]=have_align, bits[1]=have_value,
// bits[2]=is_comptime, bits[3]=have_type_body
static void wipMembersNextField(WipMembers* wm, bool bits[4]) {
    uint32_t fields_per_u32 = 8; // 32 / 4
    uint32_t index = wm->field_bits_start + wm->field_index / fields_per_u32;
    uint32_t bit_bag
        = (wm->field_index % fields_per_u32 == 0) ? 0 : wm->payload[index];
    bit_bag >>= 4;
    for (int i = 0; i < 4; i++) {
        bit_bag |= ((uint32_t)(bits[i] ? 1 : 0)) << (32 - 4 + i);
    }
    wm->payload[index] = bit_bag;
    wm->field_index++;
}

static void wipMembersAppendToField(WipMembers* wm, uint32_t data) {
    wm->payload[wm->fields_end] = data;
    wm->fields_end++;
}

static void wipMembersFinishBits(WipMembers* wm) {
    uint32_t fields_per_u32 = 8; // 32 / 4
    uint32_t empty_field_slots
        = fields_per_u32 - (wm->field_index % fields_per_u32);
    if (wm->field_index > 0 && empty_field_slots < fields_per_u32) {
        uint32_t index
            = wm->field_bits_start + wm->field_index / fields_per_u32;
        wm->payload[index] >>= (empty_field_slots * 4);
    }
}

// bits_per_field = 1: bits[0]=have_value (for enum fields).
static void wipMembersNextFieldEnum(WipMembers* wm, bool have_value) {
    uint32_t fields_per_u32 = 32; // 32 / 1
    uint32_t index = wm->field_bits_start + wm->field_index / fields_per_u32;
    uint32_t bit_bag
        = (wm->field_index % fields_per_u32 == 0) ? 0 : wm->payload[index];
    bit_bag >>= 1;
    bit_bag |= ((uint32_t)(have_value ? 1 : 0)) << 31;
    wm->payload[index] = bit_bag;
    wm->field_index++;
}

static void wipMembersFinishBitsEnum(WipMembers* wm) {
    uint32_t fields_per_u32 = 32; // 32 / 1
    uint32_t empty_field_slots
        = fields_per_u32 - (wm->field_index % fields_per_u32);
    if (wm->field_index > 0 && empty_field_slots < fields_per_u32) {
        uint32_t index
            = wm->field_bits_start + wm->field_index / fields_per_u32;
        wm->payload[index] >>= empty_field_slots;
    }
}

// Returns pointer to decls region and its length.
static const uint32_t* wipMembersDeclsSlice(
    const WipMembers* wm, uint32_t* out_len) {
    *out_len = wm->decl_index;
    return wm->payload + wm->payload_top;
}

// Returns pointer to fields region (field_bits + field_data) and its length.
static const uint32_t* wipMembersFieldsSlice(
    const WipMembers* wm, uint32_t* out_len) {
    *out_len = wm->fields_end - wm->field_bits_start;
    return wm->payload + wm->field_bits_start;
}

// Append body instructions to the WipMembers bodies scratch.
static void wipMembersBodiesAppend(
    WipMembers* wm, const uint32_t* data, uint32_t len) {
    if (wm->bodies_len + len > wm->bodies_cap) {
        uint32_t new_cap = wm->bodies_cap == 0 ? 64 : wm->bodies_cap * 2;
        while (new_cap < wm->bodies_len + len)
            new_cap *= 2;
        wm->bodies = realloc(wm->bodies, new_cap * sizeof(uint32_t));
        if (!wm->bodies)
            exit(1);
        wm->bodies_cap = new_cap;
    }
    memcpy(wm->bodies + wm->bodies_len, data, len * sizeof(uint32_t));
    wm->bodies_len += len;
}

// Append body instructions with ref_table fixups to wm->bodies.
static void wipMembersBodiesAppendWithFixups(
    WipMembers* wm, AstGenCtx* ag, const uint32_t* body, uint32_t body_len) {
    for (uint32_t i = 0; i < body_len; i++) {
        uint32_t inst = body[i];
        // Grow if needed.
        if (wm->bodies_len + 1 > wm->bodies_cap) {
            uint32_t new_cap = wm->bodies_cap == 0 ? 64 : wm->bodies_cap * 2;
            wm->bodies = realloc(wm->bodies, new_cap * sizeof(uint32_t));
            if (!wm->bodies)
                exit(1);
            wm->bodies_cap = new_cap;
        }
        wm->bodies[wm->bodies_len++] = inst;
        // Check for ref fixup.
        uint32_t ref_inst;
        while (refTableFetchRemove(ag, inst, &ref_inst)) {
            if (wm->bodies_len + 1 > wm->bodies_cap) {
                uint32_t new_cap = wm->bodies_cap * 2;
                wm->bodies = realloc(wm->bodies, new_cap * sizeof(uint32_t));
                if (!wm->bodies)
                    exit(1);
                wm->bodies_cap = new_cap;
            }
            wm->bodies[wm->bodies_len++] = ref_inst;
            inst = ref_inst;
        }
    }
}

// --- containerDecl (AstGen.zig:5468) ---
// Handles container declarations as expressions (struct{}, enum{}, etc.).

static uint32_t containerDecl(
    GenZir* gz, Scope* scope, uint32_t node, uint8_t name_strategy) {
    AstGenCtx* ag = gz->astgen;
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract members based on node type (Ast.zig:2459-2470).
    uint32_t members_buf[2];
    const uint32_t* members;
    uint32_t members_len;

    switch (tag) {
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING: {
        // lhs and rhs are optional member nodes (0 = none).
        members_len = 0;
        if (nd.lhs != 0)
            members_buf[members_len++] = nd.lhs;
        if (nd.rhs != 0)
            members_buf[members_len++] = nd.rhs;
        members = members_buf;
        break;
    }
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING: {
        // extra_data[lhs..rhs] contains members.
        members = tree->extra_data.arr + nd.lhs;
        members_len = nd.rhs - nd.lhs;
        break;
    }
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING: {
        // lhs is arg node, rhs is extra index → SubRange(start, end).
        uint32_t start = tree->extra_data.arr[nd.rhs];
        uint32_t end = tree->extra_data.arr[nd.rhs + 1];
        members = tree->extra_data.arr + start;
        members_len = end - start;
        break;
    }
    default:
        SET_ERROR(ag);
        return ZIR_REF_VOID_VALUE;
    }

    // Save/clear fn_block for nested containers (AstGen.zig:5480-5482).
    void* prev_fn_block = ag->fn_block;
    ag->fn_block = NULL;

    // Extract arg node for container_decl_arg variants (AstGen.zig:5638).
    // For enum(u8), lhs is the arg node.
    uint32_t arg_node = 0; // 0 = none
    switch (tag) {
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING:
        arg_node = nd.lhs;
        break;
    default:
        break;
    }

    // Dispatch based on container keyword (AstGen.zig:5485-5536).
    uint32_t main_token = tree->nodes.main_tokens[node];
    TokenizerTag kw_tag = tree->tokens.tags[main_token];
    uint32_t decl_inst;
    switch (kw_tag) {
    case TOKEN_KEYWORD_STRUCT: {
        // Extract layout from token before main_token (AstGen.zig:5489-5493).
        // auto=0, extern=1, packed=2.
        uint8_t layout = 0; // auto
        if (main_token > 0) {
            TokenizerTag prev_tag = tree->tokens.tags[main_token - 1];
            if (prev_tag == TOKEN_KEYWORD_PACKED)
                layout = 2;
            else if (prev_tag == TOKEN_KEYWORD_EXTERN)
                layout = 1;
        }
        decl_inst = structDeclInner(ag, gz, node, members, members_len, layout,
            arg_node, name_strategy);
        break;
    }
    case TOKEN_KEYWORD_ENUM:
        decl_inst = enumDeclInner(
            ag, gz, node, members, members_len, arg_node, name_strategy);
        break;
    default:
        // union/opaque: fall back to struct for now.
        decl_inst = structDeclInner(
            ag, gz, node, members, members_len, 0, 0, name_strategy);
        break;
    }
    (void)scope;

    ag->fn_block = prev_fn_block;
    return decl_inst + ZIR_REF_START_INDEX;
}

// --- EnumDecl.Small packing (Zir.zig EnumDecl.Small) ---

typedef struct {
    bool has_tag_type;
    bool has_captures_len;
    bool has_body_len;
    bool has_fields_len;
    bool has_decls_len;
    uint8_t name_strategy; // 2 bits
    bool nonexhaustive;
} EnumDeclSmall;

static uint16_t packEnumDeclSmall(EnumDeclSmall s) {
    uint16_t r = 0;
    if (s.has_tag_type)
        r |= (1u << 0);
    if (s.has_captures_len)
        r |= (1u << 1);
    if (s.has_body_len)
        r |= (1u << 2);
    if (s.has_fields_len)
        r |= (1u << 3);
    if (s.has_decls_len)
        r |= (1u << 4);
    r |= (uint16_t)(s.name_strategy & 0x3u) << 5;
    if (s.nonexhaustive)
        r |= (1u << 7);
    return r;
}

// Mirrors GenZir.setEnum (AstGen.zig:13064-13123).
static void setEnum(AstGenCtx* ag, uint32_t inst, uint32_t src_node,
    uint32_t tag_type, uint32_t captures_len, uint32_t body_len,
    uint32_t fields_len, uint32_t decls_len, bool nonexhaustive,
    uint8_t name_strategy) {
    EnumDeclSmall small;
    memset(&small, 0, sizeof(small));
    small.has_tag_type = (tag_type != ZIR_REF_NONE);
    small.has_captures_len = (captures_len != 0);
    small.has_body_len = (body_len != 0);
    small.has_fields_len = (fields_len != 0);
    small.has_decls_len = (decls_len != 0);
    small.name_strategy = name_strategy;
    small.nonexhaustive = nonexhaustive;

    ensureExtraCapacity(ag, 6 + 5);

    uint32_t payload_index = ag->extra_len;

    // fields_hash (4 words): zero-filled; hash comparison skipped in tests.
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;
    ag->extra[ag->extra_len++] = 0;

    ag->extra[ag->extra_len++] = ag->source_line;
    ag->extra[ag->extra_len++] = src_node;

    // Trailing data in upstream order (AstGen.zig:13092-13106).
    if (small.has_tag_type)
        ag->extra[ag->extra_len++] = tag_type;
    if (small.has_captures_len)
        ag->extra[ag->extra_len++] = captures_len;
    if (small.has_body_len)
        ag->extra[ag->extra_len++] = body_len;
    if (small.has_fields_len)
        ag->extra[ag->extra_len++] = fields_len;
    if (small.has_decls_len)
        ag->extra[ag->extra_len++] = decls_len;

    ag->inst_tags[inst] = ZIR_INST_EXTENDED;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.extended.opcode = (uint16_t)ZIR_EXT_ENUM_DECL;
    data.extended.small = packEnumDeclSmall(small);
    data.extended.operand = payload_index;
    ag->inst_datas[inst] = data;
}

// Returns true if the identifier token at `ident_token` is "_".
static bool tokenIsUnderscore(const Ast* tree, uint32_t ident_token) {
    uint32_t start = tree->tokens.starts[ident_token];
    const char* src = tree->source;
    if (src[start] != '_')
        return false;
    // Check that the next character is not alphanumeric/underscore
    // (i.e., the identifier is exactly "_").
    char next = src[start + 1];
    if ((next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z')
        || (next >= '0' && next <= '9') || next == '_')
        return false;
    return true;
}

// --- enumDeclInner (AstGen.zig:5508-5728) ---
// Handles enum container declarations.
// arg_node: the tag type expression node (e.g. u8 in enum(u8)), 0 if none.

static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint32_t arg_node,
    uint8_t name_strategy) {
    const Ast* tree = ag->tree;

    // --- First pass: count fields, values, decls, detect nonexhaustive ---
    // (AstGen.zig:5513-5590)
    uint32_t total_fields = 0;
    uint32_t decl_count = 0;
    uint32_t nonexhaustive_index = UINT32_MAX; // index into members[]
    for (uint32_t i = 0; i < members_len; i++) {
        uint32_t member_node = members[i];
        AstNodeTag mtag = tree->nodes.tags[member_node];
        switch (mtag) {
        case AST_NODE_CONTAINER_FIELD_INIT:
        case AST_NODE_CONTAINER_FIELD_ALIGN:
        case AST_NODE_CONTAINER_FIELD: {
            uint32_t main_token = tree->nodes.main_tokens[member_node];
            // Check for "_" (nonexhaustive marker).
            if (tokenIsUnderscore(tree, main_token)) {
                nonexhaustive_index = i;
                continue;
            }
            total_fields++;
            break;
        }
        default:
            decl_count++;
            break;
        }
    }
    bool nonexhaustive = (nonexhaustive_index != UINT32_MAX);

    uint32_t decl_inst = reserveInstructionIndex(ag);
    gzAppendInstruction(gz, decl_inst);

    // Create namespace scope (AstGen.zig:5618-5623).
    ScopeNamespace namespace;
    scopeNamespaceInit(
        &namespace, &gz->base, node, decl_inst, gz, ag->within_fn);

    advanceSourceCursorToNode(ag, node);

    // scanContainer to register names in string table (AstGen.zig:5635).
    scanContainer(ag, &namespace, members, members_len);

    // Set up block_scope for tag value expressions (AstGen.zig:5624-5632).
    GenZir block_scope;
    memset(&block_scope, 0, sizeof(block_scope));
    block_scope.base.tag = SCOPE_GEN_ZIR;
    block_scope.parent = &namespace.base;
    block_scope.astgen = ag;
    block_scope.decl_node_index = node;
    block_scope.decl_line = ag->source_line;
    block_scope.is_comptime = true;
    block_scope.instructions_top = ag->scratch_inst_len;
    block_scope.any_defer_node = UINT32_MAX;

    // Evaluate tag type argument if present (AstGen.zig:5638-5641).
    uint32_t arg_inst = ZIR_REF_NONE;
    if (arg_node != 0)
        arg_inst = typeExpr(&block_scope, &block_scope.base, arg_node);

    // WipMembers with bits_per_field=1, max_field_size=2 (AstGen.zig:5645).
    WipMembers wm = wipMembersInitEx(decl_count, total_fields, 1, 2);

    // --- Second pass: process members (AstGen.zig:5656-5693) ---
    for (uint32_t i = 0; i < members_len; i++) {
        uint32_t member_node = members[i];
        // Skip nonexhaustive marker field (AstGen.zig:5657-5658).
        if (i == nonexhaustive_index)
            continue;
        AstNodeTag mtag = tree->nodes.tags[member_node];
        switch (mtag) {
        case AST_NODE_COMPTIME:
            comptimeDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_SIMPLE_VAR_DECL:
        case AST_NODE_GLOBAL_VAR_DECL:
        case AST_NODE_LOCAL_VAR_DECL:
        case AST_NODE_ALIGNED_VAR_DECL:
            globalVarDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_FN_DECL:
            fnDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_TEST_DECL:
            testDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_CONTAINER_FIELD_INIT:
        case AST_NODE_CONTAINER_FIELD_ALIGN:
        case AST_NODE_CONTAINER_FIELD: {
            // Enum field (AstGen.zig:5669-5692).
            uint32_t main_token = tree->nodes.main_tokens[member_node];
            uint32_t field_name = identAsString(ag, main_token);
            wipMembersAppendToField(&wm, field_name);

            // Extract value expression.
            AstData mnd = tree->nodes.datas[member_node];
            uint32_t value_node = 0;
            if (mtag == AST_NODE_CONTAINER_FIELD_INIT) {
                value_node = mnd.rhs;
            } else if (mtag == AST_NODE_CONTAINER_FIELD && mnd.rhs != 0) {
                value_node = tree->extra_data.arr[mnd.rhs + 1];
            }

            bool have_value = (value_node != 0);
            wipMembersNextFieldEnum(&wm, have_value);

            // Evaluate tag value expression (AstGen.zig:5690-5691).
            if (have_value) {
                ResultLoc val_rl = { .tag = RL_COERCED_TY,
                    .data = arg_inst,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                uint32_t tag_value_inst = exprRl(
                    &block_scope, &block_scope.base, val_rl, value_node);
                wipMembersAppendToField(&wm, tag_value_inst);
            }
            break;
        }
        default:
            SET_ERROR(ag);
            break;
        }
    }

    // Emit break_inline if block_scope has instructions
    // (AstGen.zig:5695-5697).
    if (gzInstructionsLen(&block_scope) > 0) {
        addBreak(&block_scope, ZIR_INST_BREAK_INLINE, decl_inst,
            ZIR_REF_VOID_VALUE, AST_NODE_OFFSET_NONE);
    }

    uint32_t raw_body_len = gzInstructionsLen(&block_scope);
    const uint32_t* body = gzInstructionsSlice(&block_scope);
    uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_body_len);

    // setEnum (AstGen.zig:5705-5715).
    setEnum(ag, decl_inst, node, arg_inst, namespace.captures_len, body_len,
        total_fields, decl_count, nonexhaustive, name_strategy);

    wipMembersFinishBitsEnum(&wm);

    // Append trailing data (AstGen.zig:5718-5725):
    // captures, decls, body, fields.
    uint32_t decls_len_out;
    const uint32_t* decls_slice = wipMembersDeclsSlice(&wm, &decls_len_out);
    uint32_t fields_len_out;
    const uint32_t* fields_slice = wipMembersFieldsSlice(&wm, &fields_len_out);

    ensureExtraCapacity(ag,
        namespace.captures_len * 2 + decls_len_out + body_len
            + fields_len_out);
    // Captures (AstGen.zig:5721-5722).
    for (uint32_t i = 0; i < namespace.captures_len; i++)
        ag->extra[ag->extra_len++] = namespace.capture_keys[i];
    for (uint32_t i = 0; i < namespace.captures_len; i++)
        ag->extra[ag->extra_len++] = namespace.capture_vals[i];
    for (uint32_t i = 0; i < decls_len_out; i++)
        ag->extra[ag->extra_len++] = decls_slice[i];
    // Body instructions with fixups (AstGen.zig:5724).
    for (uint32_t i = 0; i < raw_body_len; i++)
        appendPossiblyRefdBodyInst(ag, body[i]);
    // Fields (bit bags + field data).
    for (uint32_t i = 0; i < fields_len_out; i++)
        ag->extra[ag->extra_len++] = fields_slice[i];

    gzUnstack(&block_scope);
    wipMembersDeinit(&wm);
    scopeNamespaceDeinit(&namespace);
    return decl_inst;
}

// --- tupleDecl (AstGen.zig:5192) ---

static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint8_t layout,
    uint32_t backing_int_node) {
    const Ast* tree = ag->tree;

    // layout must be auto for tuples (AstGen.zig:5204-5207).
    if (layout != 0) {
        SET_ERROR(ag);
        return reserveInstructionIndex(ag);
    }
    // tuples don't support backing int (AstGen.zig:5209-5211).
    if (backing_int_node != 0) {
        SET_ERROR(ag);
        return reserveInstructionIndex(ag);
    }

    // Build fields_start scratch area: for each field, type ref + init ref.
    uint32_t fields_start = ag->extra_len;
    // We use extra as scratch temporarily; will finalize below.
    // Actually, upstream uses astgen.scratch; we use a temporary buffer.
    uint32_t* tuple_scratch = NULL;
    uint32_t tuple_scratch_len = 0;
    uint32_t tuple_scratch_cap = 0;

    for (uint32_t i = 0; i < members_len; i++) {
        uint32_t member_node = members[i];
        AstNodeTag mtag = tree->nodes.tags[member_node];

        // Non-field nodes are errors in tuples (AstGen.zig:5224-5238).
        if (mtag != AST_NODE_CONTAINER_FIELD_INIT
            && mtag != AST_NODE_CONTAINER_FIELD_ALIGN
            && mtag != AST_NODE_CONTAINER_FIELD) {
            SET_ERROR(ag);
            free(tuple_scratch);
            return reserveInstructionIndex(ag);
        }

        // Extract field info.
        uint32_t main_token = tree->nodes.main_tokens[member_node];
        AstData nd = tree->nodes.datas[member_node];
        uint32_t type_node = nd.lhs;
        uint32_t align_node = 0;
        uint32_t value_node = 0;
        bool has_comptime_token = false;

        switch (mtag) {
        case AST_NODE_CONTAINER_FIELD_INIT:
            value_node = nd.rhs;
            break;
        case AST_NODE_CONTAINER_FIELD_ALIGN:
            align_node = nd.rhs;
            break;
        case AST_NODE_CONTAINER_FIELD:
            if (nd.rhs != 0) {
                align_node = tree->extra_data.arr[nd.rhs];
                value_node = tree->extra_data.arr[nd.rhs + 1];
            }
            break;
        default:
            break;
        }

        if (main_token > 0
            && tree->tokens.tags[main_token - 1] == TOKEN_KEYWORD_COMPTIME) {
            has_comptime_token = true;
        }

        // Check tuple_like: must be tuple-like (AstGen.zig:5240-5241).
        bool tuple_like = tree->tokens.tags[main_token] != TOKEN_IDENTIFIER
            || tree->tokens.tags[main_token + 1] != TOKEN_COLON;
        if (!tuple_like) {
            // Named field in tuple: error (AstGen.zig:5241).
            SET_ERROR(ag);
            free(tuple_scratch);
            return reserveInstructionIndex(ag);
        }

        // Tuple fields cannot have alignment (AstGen.zig:5244-5246).
        if (align_node != 0) {
            SET_ERROR(ag);
            free(tuple_scratch);
            return reserveInstructionIndex(ag);
        }

        // Non-comptime tuple field with default init: error
        // (AstGen.zig:5248-5250).
        if (value_node != 0 && !has_comptime_token) {
            SET_ERROR(ag);
            free(tuple_scratch);
            return reserveInstructionIndex(ag);
        }

        // Comptime field without default init: error
        // (AstGen.zig:5252-5254).
        if (value_node == 0 && has_comptime_token) {
            SET_ERROR(ag);
            free(tuple_scratch);
            return reserveInstructionIndex(ag);
        }

        // Type expression (AstGen.zig:5256).
        uint32_t field_type_ref = typeExpr(gz, &gz->base, type_node);

        // Grow scratch buffer.
        if (tuple_scratch_len + 2 > tuple_scratch_cap) {
            uint32_t new_cap
                = tuple_scratch_cap == 0 ? 16 : tuple_scratch_cap * 2;
            tuple_scratch = realloc(tuple_scratch, new_cap * sizeof(uint32_t));
            if (!tuple_scratch)
                exit(1);
            tuple_scratch_cap = new_cap;
        }
        tuple_scratch[tuple_scratch_len++] = field_type_ref;

        // Default init (AstGen.zig:5259-5264).
        if (value_node != 0) {
            ResultLoc init_rl = { .tag = RL_COERCED_TY,
                .data = field_type_ref,
                .src_node = 0,
                .ctx = RI_CTX_NONE };
            uint32_t field_init_ref = comptimeExpr(gz, &gz->base, init_rl,
                value_node, COMPTIME_REASON_TUPLE_FIELD_DEFAULT_VALUE);
            tuple_scratch[tuple_scratch_len++] = field_init_ref;
        } else {
            tuple_scratch[tuple_scratch_len++] = ZIR_REF_NONE;
        }
    }

    if (members_len > 65535) {
        SET_ERROR(ag);
        free(tuple_scratch);
        return reserveInstructionIndex(ag);
    }
    uint16_t fields_len = (uint16_t)members_len;

    // Write TupleDecl payload (AstGen.zig:5274-5286).
    (void)fields_start;
    ensureExtraCapacity(ag, 1 + tuple_scratch_len);
    uint32_t payload_index = ag->extra_len;
    // src_node as node offset relative to gz->decl_node_index.
    ag->extra[ag->extra_len++]
        = (uint32_t)((int32_t)node - (int32_t)gz->decl_node_index);

    for (uint32_t i = 0; i < tuple_scratch_len; i++)
        ag->extra[ag->extra_len++] = tuple_scratch[i];

    free(tuple_scratch);

    // Emit extended instruction (AstGen.zig:5279-5286).
    ensureInstCapacity(ag, 1);
    uint32_t idx = ag->inst_len;
    ag->inst_tags[idx] = ZIR_INST_EXTENDED;
    ZirInstData data;
    memset(&data, 0, sizeof(data));
    data.extended.opcode = (uint16_t)ZIR_EXT_TUPLE_DECL;
    data.extended.small = fields_len;
    data.extended.operand = payload_index;
    ag->inst_datas[idx] = data;
    ag->inst_len++;
    gzAppendInstruction(gz, idx);
    return idx;
}

// --- structDeclInner (AstGen.zig:4926) ---

static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
    const uint32_t* members, uint32_t members_len, uint8_t layout,
    uint32_t backing_int_node, uint8_t name_strategy) {
    const Ast* tree = ag->tree;

    // Tuple detection (AstGen.zig:4939-4950).
    // Scan for tuple-like fields; if any found, dispatch to tupleDecl.
    for (uint32_t i = 0; i < members_len; i++) {
        uint32_t member_node = members[i];
        AstNodeTag mtag = tree->nodes.tags[member_node];
        if (mtag != AST_NODE_CONTAINER_FIELD_INIT
            && mtag != AST_NODE_CONTAINER_FIELD_ALIGN
            && mtag != AST_NODE_CONTAINER_FIELD)
            continue;
        uint32_t main_token = tree->nodes.main_tokens[member_node];
        bool tuple_like = tree->tokens.tags[main_token] != TOKEN_IDENTIFIER
            || tree->tokens.tags[main_token + 1] != TOKEN_COLON;
        if (tuple_like) {
            if (node == 0) {
                // Root node: file cannot be a tuple
                // (AstGen.zig:4946).
                SET_ERROR(ag);
                return reserveInstructionIndex(ag);
            }
            return tupleDecl(
                ag, gz, node, members, members_len, layout, backing_int_node);
        }
    }

    uint32_t decl_inst = reserveInstructionIndex(ag);
    gzAppendInstruction(gz, decl_inst);

    // Fast path: no members, no backing int (AstGen.zig:4954-4970).
    if (members_len == 0 && backing_int_node == 0) {
        StructDeclSmall small;
        memset(&small, 0, sizeof(small));
        small.layout = layout;
        small.name_strategy = name_strategy;
        setStruct(ag, decl_inst, node, small, 0, 0, 0);
        return decl_inst;
    }

    // Non-empty container (AstGen.zig:4973-5189).

    // Create namespace scope (AstGen.zig:4973-4979).
    ScopeNamespace namespace;
    scopeNamespaceInit(
        &namespace, &gz->base, node, decl_inst, gz, ag->within_fn);

    advanceSourceCursorToNode(ag, node);

    uint32_t decl_count = scanContainer(ag, &namespace, members, members_len);
    uint32_t field_count = members_len - decl_count;

    WipMembers wm = wipMembersInit(decl_count, field_count);

    // Set up block_scope for field type/align/init expressions.
    // (AstGen.zig:4986-4994)
    GenZir block_scope;
    memset(&block_scope, 0, sizeof(block_scope));
    block_scope.base.tag = SCOPE_GEN_ZIR;
    block_scope.parent = &namespace.base;
    block_scope.astgen = ag;
    block_scope.decl_node_index = node;
    block_scope.decl_line = gz->decl_line; // Fix #7: use gz->decl_line
    block_scope.is_comptime = true;
    block_scope.instructions_top = ag->scratch_inst_len;
    block_scope.any_defer_node = UINT32_MAX;

    // Handle backing_int_node for packed structs (AstGen.zig:5000-5024).
    // We store the raw body instructions and apply fixups at the final append.
    uint32_t backing_int_body_raw_len = 0;
    uint32_t backing_int_ref = ZIR_REF_NONE;
    uint32_t* backing_int_body_raw = NULL;
    if (backing_int_node != 0) {
        if (layout != 2) { // not packed
            SET_ERROR(ag); // non-packed struct with backing int
        } else {
            backing_int_ref
                = typeExpr(&block_scope, &block_scope.base, backing_int_node);
            if (gzInstructionsLen(&block_scope) > 0) {
                if (!endsWithNoReturn(&block_scope)) {
                    makeBreakInline(&block_scope, decl_inst, backing_int_ref,
                        AST_NODE_OFFSET_NONE);
                }
                backing_int_body_raw_len = gzInstructionsLen(&block_scope);
                const uint32_t* body = gzInstructionsSlice(&block_scope);
                backing_int_body_raw
                    = malloc(backing_int_body_raw_len * sizeof(uint32_t));
                if (!backing_int_body_raw)
                    exit(1);
                memcpy(backing_int_body_raw, body,
                    backing_int_body_raw_len * sizeof(uint32_t));
                ag->scratch_inst_len = block_scope.instructions_top;
            }
        }
    }

    bool known_non_opv = false;
    bool known_comptime_only = false;
    bool any_comptime_fields = false;
    bool any_aligned_fields = false;
    bool any_default_inits = false;

    // Process each member (AstGen.zig:5060-5147).
    for (uint32_t i = 0; i < members_len; i++) {
        uint32_t member_node = members[i];
        AstNodeTag mtag = tree->nodes.tags[member_node];
        switch (mtag) {
        case AST_NODE_COMPTIME:
            comptimeDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_SIMPLE_VAR_DECL:
            globalVarDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_TEST_DECL:
            testDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_FN_DECL:
            fnDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        // fn_proto* dispatch (AstGen.zig:5809-5813, issue #9).
        case AST_NODE_FN_PROTO_SIMPLE:
        case AST_NODE_FN_PROTO_MULTI:
        case AST_NODE_FN_PROTO_ONE:
        case AST_NODE_FN_PROTO:
            fnDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_USINGNAMESPACE:
        case AST_NODE_GLOBAL_VAR_DECL:
        case AST_NODE_LOCAL_VAR_DECL:
        case AST_NODE_ALIGNED_VAR_DECL:
            globalVarDecl(ag, gz, &namespace.base, wm.payload, &wm.decl_index,
                member_node);
            break;
        case AST_NODE_CONTAINER_FIELD_INIT:
        case AST_NODE_CONTAINER_FIELD_ALIGN:
        case AST_NODE_CONTAINER_FIELD: {
            // Extract field info from AST node (Ast.zig:1413-1454).
            uint32_t main_token = tree->nodes.main_tokens[member_node];
            AstData nd = tree->nodes.datas[member_node];
            uint32_t type_node = nd.lhs;
            uint32_t align_node = 0;
            uint32_t value_node = 0;
            bool has_comptime_token = false;

            switch (mtag) {
            case AST_NODE_CONTAINER_FIELD_INIT:
                // lhs = type_expr, rhs = value_expr (optional, 0=none)
                value_node = nd.rhs;
                break;
            case AST_NODE_CONTAINER_FIELD_ALIGN:
                // lhs = type_expr, rhs = align_expr
                align_node = nd.rhs;
                break;
            case AST_NODE_CONTAINER_FIELD:
                // lhs = type_expr, rhs = extra index to {align, value}
                if (nd.rhs != 0) {
                    align_node = tree->extra_data.arr[nd.rhs];
                    value_node = tree->extra_data.arr[nd.rhs + 1];
                }
                break;
            default:
                break;
            }

            // Check for comptime token preceding main_token
            // (Ast.zig:2071-2082).
            if (main_token > 0
                && tree->tokens.tags[main_token - 1]
                    == TOKEN_KEYWORD_COMPTIME) {
                has_comptime_token = true;
            }

            // Field name (AstGen.zig:5068).
            // convertToNonTupleLike: for struct fields, if type_expr is
            // an identifier node, it's actually a named field with the
            // identifier as the name (AstGen.zig:5069-5070).
            uint32_t field_name = identAsString(ag, main_token);
            wipMembersAppendToField(&wm, field_name);

            // Type expression: struct field missing type is an error
            // (AstGen.zig:5073-5075, issue #12).
            if (type_node == 0) {
                SET_ERROR(ag);
                break;
            }

            bool have_type_body = false;
            uint32_t field_type = 0;
            field_type = typeExpr(&block_scope, &block_scope.base, type_node);
            have_type_body = (gzInstructionsLen(&block_scope) > 0);

            bool have_align = (align_node != 0);
            bool have_value = (value_node != 0);
            bool is_comptime = has_comptime_token;

            // Packed/extern struct comptime field error
            // (AstGen.zig:5083-5087, issue #15).
            if (is_comptime) {
                if (layout == 2 || layout == 1) {
                    // packed or extern struct fields cannot be comptime.
                    SET_ERROR(ag);
                    break;
                }
                any_comptime_fields = true;
            } else {
                // (AstGen.zig:5089-5093)
                known_non_opv = known_non_opv
                    || nodeImpliesMoreThanOnePossibleValue(tree, type_node);
                known_comptime_only = known_comptime_only
                    || nodeImpliesComptimeOnly(tree, type_node);
            }

            bool field_bits[4]
                = { have_align, have_value, is_comptime, have_type_body };
            wipMembersNextField(&wm, field_bits);

            if (have_type_body) {
                // Emit break_inline to carry the type value
                // (AstGen.zig:5097-5099).
                if (!endsWithNoReturn(&block_scope)) {
                    makeBreakInline(&block_scope, decl_inst, field_type,
                        AST_NODE_OFFSET_NONE);
                }
                uint32_t raw_len = gzInstructionsLen(&block_scope);
                const uint32_t* body = gzInstructionsSlice(&block_scope);
                uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_len);
                uint32_t bodies_before = wm.bodies_len;
                wipMembersBodiesAppendWithFixups(&wm, ag, body, raw_len);
                (void)bodies_before;
                wipMembersAppendToField(&wm, body_len);
                // Reset block_scope.
                ag->scratch_inst_len = block_scope.instructions_top;
            } else {
                wipMembersAppendToField(&wm, field_type);
            }

            if (have_align) {
                // Packed struct fields cannot have alignment overrides
                // (AstGen.zig:5111-5113, issue #15).
                if (layout == 2) { // packed
                    SET_ERROR(ag);
                    break;
                }
                any_aligned_fields = true;
                // Use coerced_align_ri: RL_COERCED_TY with u29_type
                // (AstGen.zig:5115, issue #14).
                ResultLoc align_rl = { .tag = RL_COERCED_TY,
                    .data = ZIR_REF_U29_TYPE,
                    .src_node = 0,
                    .ctx = RI_CTX_NONE };
                uint32_t align_ref = exprRl(
                    &block_scope, &block_scope.base, align_rl, align_node);
                if (!endsWithNoReturn(&block_scope)) {
                    makeBreakInline(&block_scope, decl_inst, align_ref,
                        AST_NODE_OFFSET_NONE);
                }
                uint32_t raw_len = gzInstructionsLen(&block_scope);
                const uint32_t* body = gzInstructionsSlice(&block_scope);
                uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_len);
                wipMembersBodiesAppendWithFixups(&wm, ag, body, raw_len);
                wipMembersAppendToField(&wm, body_len);
                ag->scratch_inst_len = block_scope.instructions_top;
            }

            if (have_value) {
                any_default_inits = true;
                // Use coerced_ty with decl_inst when field type is present
                // (AstGen.zig:5132, issue #11).
                ResultLoc value_rl;
                if (field_type == 0) {
                    value_rl = RL_NONE_VAL;
                } else {
                    uint32_t dref = decl_inst + ZIR_REF_START_INDEX;
                    value_rl = (ResultLoc) { .tag = RL_COERCED_TY,
                        .data = dref,
                        .src_node = 0,
                        .ctx = RI_CTX_NONE };
                }
                uint32_t default_ref = exprRl(
                    &block_scope, &block_scope.base, value_rl, value_node);
                if (!endsWithNoReturn(&block_scope)) {
                    makeBreakInline(&block_scope, decl_inst, default_ref,
                        AST_NODE_OFFSET_NONE);
                }
                uint32_t raw_len = gzInstructionsLen(&block_scope);
                const uint32_t* body = gzInstructionsSlice(&block_scope);
                uint32_t body_len = countBodyLenAfterFixups(ag, body, raw_len);
                wipMembersBodiesAppendWithFixups(&wm, ag, body, raw_len);
                wipMembersAppendToField(&wm, body_len);
                ag->scratch_inst_len = block_scope.instructions_top;
            } else if (has_comptime_token) {
                // Comptime field without default init: error
                // (AstGen.zig:5144-5145, issue #13).
                SET_ERROR(ag);
            }
            break;
        }
        default:
            SET_ERROR(ag);
            break;
        }
    }

    wipMembersFinishBits(&wm);

    // setStruct (AstGen.zig:5152-5166).
    StructDeclSmall small;
    memset(&small, 0, sizeof(small));
    small.has_captures_len = (namespace.captures_len > 0);
    small.has_decls_len = (decl_count > 0);
    small.has_fields_len = (field_count > 0);
    small.has_backing_int = (backing_int_ref != ZIR_REF_NONE);
    small.known_non_opv = known_non_opv;
    small.known_comptime_only = known_comptime_only;
    small.any_comptime_fields = any_comptime_fields;
    small.any_default_inits = any_default_inits;
    small.any_aligned_fields = any_aligned_fields;
    small.layout = layout;
    small.name_strategy = name_strategy;
    setStruct(ag, decl_inst, node, small, namespace.captures_len, field_count,
        decl_count);

    // Append: captures, backing_int, decls, fields, bodies
    // (AstGen.zig:5172-5186).
    uint32_t decls_len;
    const uint32_t* decls_slice = wipMembersDeclsSlice(&wm, &decls_len);
    uint32_t fields_len;
    const uint32_t* fields_slice = wipMembersFieldsSlice(&wm, &fields_len);

    // Compute backing_int_body_len (with fixups) for capacity estimation.
    uint32_t backing_int_body_len = 0;
    if (backing_int_body_raw_len > 0) {
        backing_int_body_len = countBodyLenAfterFixups(
            ag, backing_int_body_raw, backing_int_body_raw_len);
    }
    ensureExtraCapacity(ag,
        namespace.captures_len * 2
            + (backing_int_ref != ZIR_REF_NONE ? backing_int_body_len + 2 : 0)
            + decls_len + fields_len + wm.bodies_len);
    // Captures (AstGen.zig:5174-5175).
    for (uint32_t i = 0; i < namespace.captures_len; i++)
        ag->extra[ag->extra_len++] = namespace.capture_keys[i];
    for (uint32_t i = 0; i < namespace.captures_len; i++)
        ag->extra[ag->extra_len++] = namespace.capture_vals[i];
    // backing_int (AstGen.zig:5176-5183).
    if (backing_int_ref != ZIR_REF_NONE) {
        ag->extra[ag->extra_len++] = backing_int_body_len;
        if (backing_int_body_len == 0) {
            ag->extra[ag->extra_len++] = backing_int_ref;
        } else {
            for (uint32_t j = 0; j < backing_int_body_raw_len; j++)
                appendPossiblyRefdBodyInst(ag, backing_int_body_raw[j]);
        }
    }
    free(backing_int_body_raw);
    for (uint32_t i = 0; i < decls_len; i++)
        ag->extra[ag->extra_len++] = decls_slice[i];
    for (uint32_t i = 0; i < fields_len; i++)
        ag->extra[ag->extra_len++] = fields_slice[i];
    for (uint32_t i = 0; i < wm.bodies_len; i++)
        ag->extra[ag->extra_len++] = wm.bodies[i];

    gzUnstack(&block_scope);
    wipMembersDeinit(&wm);
    scopeNamespaceDeinit(&namespace);
    return decl_inst;
}

// --- AstRlAnnotate (AstRlAnnotate.zig) ---
// Pre-pass to determine which AST nodes need result locations.

typedef struct {
    bool have_type;
    bool have_ptr;
} RlResultInfo;

#define RL_RI_NONE ((RlResultInfo) { false, false })
#define RL_RI_TYPED_PTR ((RlResultInfo) { true, true })
#define RL_RI_INFERRED_PTR ((RlResultInfo) { false, true })
#define RL_RI_TYPE_ONLY ((RlResultInfo) { true, false })

// Block for label tracking (AstRlAnnotate.zig:56-62).
typedef struct RlBlock {
    struct RlBlock* parent;
    uint32_t label_token; // UINT32_MAX = no label
    bool is_loop;
    RlResultInfo ri;
    bool consumes_res_ptr;
} RlBlock;

static void nodesNeedRlAdd(AstGenCtx* ag, uint32_t node) {
    if (ag->nodes_need_rl_len >= ag->nodes_need_rl_cap) {
        uint32_t new_cap
            = ag->nodes_need_rl_cap == 0 ? 16 : ag->nodes_need_rl_cap * 2;
        ag->nodes_need_rl
            = realloc(ag->nodes_need_rl, new_cap * sizeof(uint32_t));
        ag->nodes_need_rl_cap = new_cap;
    }
    ag->nodes_need_rl[ag->nodes_need_rl_len++] = node;
}

static bool nodesNeedRlContains(const AstGenCtx* ag, uint32_t node) {
    for (uint32_t i = 0; i < ag->nodes_need_rl_len; i++) {
        if (ag->nodes_need_rl[i] == node)
            return true;
    }
    return false;
}

// Compare two identifier tokens by their source text.
// Handles both regular identifiers and @"..."-quoted identifiers.
static bool rlTokenIdentEqual(
    const Ast* tree, uint32_t tok_a, uint32_t tok_b) {
    const char* src = tree->source;
    uint32_t a_start = tree->tokens.starts[tok_a];
    uint32_t b_start = tree->tokens.starts[tok_b];
    bool a_quoted = (src[a_start] == '@');
    bool b_quoted = (src[b_start] == '@');
    if (a_quoted != b_quoted)
        return false;
    if (a_quoted) {
        // Both are @"..."-quoted: skip '@"' prefix, compare up to '"'.
        uint32_t ai = a_start + 2;
        uint32_t bi = b_start + 2;
        for (;;) {
            char ca = src[ai];
            char cb = src[bi];
            if (ca == '"' && cb == '"')
                return true;
            if (ca == '"' || cb == '"')
                return false;
            if (ca != cb)
                return false;
            ai++;
            bi++;
        }
    }
    for (uint32_t i = 0;; i++) {
        char ca = src[a_start + i];
        char cb = src[b_start + i];
        bool a_id = (ca >= 'a' && ca <= 'z') || (ca >= 'A' && ca <= 'Z')
            || (ca >= '0' && ca <= '9') || ca == '_';
        bool b_id = (cb >= 'a' && cb <= 'z') || (cb >= 'A' && cb <= 'Z')
            || (cb >= '0' && cb <= '9') || cb == '_';
        if (!a_id && !b_id)
            return true;
        if (!a_id || !b_id)
            return false;
        if (ca != cb)
            return false;
    }
}

// Forward declarations.
static bool rlExpr(
    AstGenCtx* ag, uint32_t node, RlBlock* block, RlResultInfo ri);
static void rlContainerDecl(AstGenCtx* ag, RlBlock* block, uint32_t node);
static bool rlBlockExpr(AstGenCtx* ag, RlBlock* parent_block, RlResultInfo ri,
    uint32_t node, const uint32_t* stmts, uint32_t count);
static bool rlBuiltinCall(AstGenCtx* ag, RlBlock* block, uint32_t node,
    const uint32_t* args, uint32_t nargs);

// containerDecl (AstRlAnnotate.zig:89-127).
static void rlContainerDecl(AstGenCtx* ag, RlBlock* block, uint32_t node) {
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    // Extract arg and members depending on variant.
    // All container decls: recurse arg with type_only, members with none.
    // (The keyword type — struct/union/enum/opaque — doesn't matter for RL.)
    uint32_t member_buf[2];
    const uint32_t* members = NULL;
    uint32_t members_len = 0;
    uint32_t arg_node = 0; // 0 = no arg

    switch (tag) {
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING: {
        uint32_t idx = 0;
        if (nd.lhs != 0)
            member_buf[idx++] = nd.lhs;
        if (nd.rhs != 0)
            member_buf[idx++] = nd.rhs;
        members = member_buf;
        members_len = idx;
        break;
    }
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING:
        members = tree->extra_data.arr + nd.lhs;
        members_len = nd.rhs - nd.lhs;
        break;
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING: {
        arg_node = nd.lhs;
        uint32_t extra_idx = nd.rhs;
        uint32_t start = tree->extra_data.arr[extra_idx];
        uint32_t end = tree->extra_data.arr[extra_idx + 1];
        members = tree->extra_data.arr + start;
        members_len = end - start;
        break;
    }
    default:
        return;
    }

    if (arg_node != 0)
        (void)rlExpr(ag, arg_node, block, RL_RI_TYPE_ONLY);
    for (uint32_t i = 0; i < members_len; i++)
        (void)rlExpr(ag, members[i], block, RL_RI_NONE);
}

// blockExpr (AstRlAnnotate.zig:787-814).
static bool rlBlockExpr(AstGenCtx* ag, RlBlock* parent_block, RlResultInfo ri,
    uint32_t node, const uint32_t* stmts, uint32_t count) {
    const Ast* tree = ag->tree;
    uint32_t lbrace = tree->nodes.main_tokens[node];
    bool is_labeled
        = (lbrace >= 2 && tree->tokens.tags[lbrace - 1] == TOKEN_COLON
            && tree->tokens.tags[lbrace - 2] == TOKEN_IDENTIFIER);

    if (is_labeled) {
        RlBlock new_block;
        new_block.parent = parent_block;
        new_block.label_token = lbrace - 2;
        new_block.is_loop = false;
        new_block.ri = ri;
        new_block.consumes_res_ptr = false;
        for (uint32_t i = 0; i < count; i++)
            (void)rlExpr(ag, stmts[i], &new_block, RL_RI_NONE);
        if (new_block.consumes_res_ptr)
            nodesNeedRlAdd(ag, node);
        return new_block.consumes_res_ptr;
    } else {
        for (uint32_t i = 0; i < count; i++)
            (void)rlExpr(ag, stmts[i], parent_block, RL_RI_NONE);
        return false;
    }
}

// builtinCall (AstRlAnnotate.zig:816-1100).
// Simplified: no builtin currently consumes its result location,
// so we just recurse into all args with RL_RI_NONE.
static bool rlBuiltinCall(AstGenCtx* ag, RlBlock* block, uint32_t node,
    const uint32_t* args, uint32_t nargs) {
    (void)node;
    for (uint32_t i = 0; i < nargs; i++)
        (void)rlExpr(ag, args[i], block, RL_RI_NONE);
    return false;
}

// expr (AstRlAnnotate.zig:130-771).
static bool rlExpr(
    AstGenCtx* ag, uint32_t node, RlBlock* block, RlResultInfo ri) {
    const Ast* tree = ag->tree;
    AstNodeTag tag = tree->nodes.tags[node];
    AstData nd = tree->nodes.datas[node];

    switch (tag) {
    // Unreachable nodes (AstRlAnnotate.zig:133-142).
    case AST_NODE_ROOT:
    case AST_NODE_SWITCH_CASE_ONE:
    case AST_NODE_SWITCH_CASE_INLINE_ONE:
    case AST_NODE_SWITCH_CASE:
    case AST_NODE_SWITCH_CASE_INLINE:
    case AST_NODE_SWITCH_RANGE:
    case AST_NODE_FOR_RANGE:
    case AST_NODE_ASM_OUTPUT:
    case AST_NODE_ASM_INPUT:
        return false; // unreachable in upstream

    // errdefer (AstRlAnnotate.zig:144-147).
    case AST_NODE_ERRDEFER:
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;

    // defer (AstRlAnnotate.zig:148-151).
    case AST_NODE_DEFER:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // container_field (AstRlAnnotate.zig:153-167).
    case AST_NODE_CONTAINER_FIELD_INIT: {
        // lhs = type_expr, rhs = value_expr
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        if (nd.rhs != 0)
            (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    }
    case AST_NODE_CONTAINER_FIELD_ALIGN: {
        // lhs = type_expr, rhs = align_expr
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        if (nd.rhs != 0)
            (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    }
    case AST_NODE_CONTAINER_FIELD: {
        // lhs = type_expr, rhs = extra index to {align_expr, value_expr}
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        if (nd.rhs != 0) {
            uint32_t align_node = tree->extra_data.arr[nd.rhs];
            uint32_t value_node = tree->extra_data.arr[nd.rhs + 1];
            if (align_node != 0)
                (void)rlExpr(ag, align_node, block, RL_RI_TYPE_ONLY);
            if (value_node != 0)
                (void)rlExpr(ag, value_node, block, RL_RI_TYPE_ONLY);
        }
        return false;
    }

    // test_decl (AstRlAnnotate.zig:168-171).
    case AST_NODE_TEST_DECL:
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;

    // var_decl (AstRlAnnotate.zig:172-202).
    case AST_NODE_GLOBAL_VAR_DECL:
    case AST_NODE_LOCAL_VAR_DECL:
    case AST_NODE_SIMPLE_VAR_DECL:
    case AST_NODE_ALIGNED_VAR_DECL: {
        uint32_t type_node = 0;
        uint32_t init_node = 0;
        uint32_t mut_token = tree->nodes.main_tokens[node];
        if (tag == AST_NODE_SIMPLE_VAR_DECL) {
            type_node = nd.lhs;
            init_node = nd.rhs;
        } else if (tag == AST_NODE_LOCAL_VAR_DECL
            || tag == AST_NODE_GLOBAL_VAR_DECL) {
            type_node = tree->extra_data.arr[nd.lhs];
            init_node = nd.rhs;
        } else { // ALIGNED_VAR_DECL
            init_node = nd.rhs;
        }
        RlResultInfo init_ri;
        if (type_node != 0) {
            (void)rlExpr(ag, type_node, block, RL_RI_TYPE_ONLY);
            init_ri = RL_RI_TYPED_PTR;
        } else {
            init_ri = RL_RI_INFERRED_PTR;
        }
        if (init_node == 0)
            return false;
        bool is_const = (tree->source[tree->tokens.starts[mut_token]] == 'c');
        if (is_const) {
            bool init_consumes_rl = rlExpr(ag, init_node, block, init_ri);
            if (init_consumes_rl)
                nodesNeedRlAdd(ag, node);
            return false;
        } else {
            (void)rlExpr(ag, init_node, block, init_ri);
            return false;
        }
    }

    // assign (AstRlAnnotate.zig:212-217).
    case AST_NODE_ASSIGN:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPED_PTR);
        return false;

    // compound assign (AstRlAnnotate.zig:218-240).
    case AST_NODE_ASSIGN_SHL:
    case AST_NODE_ASSIGN_SHL_SAT:
    case AST_NODE_ASSIGN_SHR:
    case AST_NODE_ASSIGN_BIT_AND:
    case AST_NODE_ASSIGN_BIT_OR:
    case AST_NODE_ASSIGN_BIT_XOR:
    case AST_NODE_ASSIGN_DIV:
    case AST_NODE_ASSIGN_SUB:
    case AST_NODE_ASSIGN_SUB_WRAP:
    case AST_NODE_ASSIGN_SUB_SAT:
    case AST_NODE_ASSIGN_MOD:
    case AST_NODE_ASSIGN_ADD:
    case AST_NODE_ASSIGN_ADD_WRAP:
    case AST_NODE_ASSIGN_ADD_SAT:
    case AST_NODE_ASSIGN_MUL:
    case AST_NODE_ASSIGN_MUL_WRAP:
    case AST_NODE_ASSIGN_MUL_SAT:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;

    // shl/shr (AstRlAnnotate.zig:241-246).
    case AST_NODE_SHL:
    case AST_NODE_SHR:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;

    // binary arithmetic/comparison (AstRlAnnotate.zig:247-274).
    case AST_NODE_ADD:
    case AST_NODE_ADD_WRAP:
    case AST_NODE_ADD_SAT:
    case AST_NODE_SUB:
    case AST_NODE_SUB_WRAP:
    case AST_NODE_SUB_SAT:
    case AST_NODE_MUL:
    case AST_NODE_MUL_WRAP:
    case AST_NODE_MUL_SAT:
    case AST_NODE_DIV:
    case AST_NODE_MOD:
    case AST_NODE_SHL_SAT:
    case AST_NODE_BIT_AND:
    case AST_NODE_BIT_OR:
    case AST_NODE_BIT_XOR:
    case AST_NODE_BANG_EQUAL:
    case AST_NODE_EQUAL_EQUAL:
    case AST_NODE_GREATER_THAN:
    case AST_NODE_GREATER_OR_EQUAL:
    case AST_NODE_LESS_THAN:
    case AST_NODE_LESS_OR_EQUAL:
    case AST_NODE_ARRAY_CAT:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;

    // array_mult (AstRlAnnotate.zig:276-281).
    case AST_NODE_ARRAY_MULT:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;

    // error_union, merge_error_sets (AstRlAnnotate.zig:282-287).
    case AST_NODE_ERROR_UNION:
    case AST_NODE_MERGE_ERROR_SETS:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;

    // bool_and, bool_or (AstRlAnnotate.zig:288-295).
    case AST_NODE_BOOL_AND:
    case AST_NODE_BOOL_OR:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;

    // bool_not (AstRlAnnotate.zig:296-299).
    case AST_NODE_BOOL_NOT:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        return false;

    // bit_not, negation, negation_wrap (AstRlAnnotate.zig:300-303).
    case AST_NODE_BIT_NOT:
    case AST_NODE_NEGATION:
    case AST_NODE_NEGATION_WRAP:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // Leaves (AstRlAnnotate.zig:305-320).
    case AST_NODE_IDENTIFIER:
    case AST_NODE_STRING_LITERAL:
    case AST_NODE_MULTILINE_STRING_LITERAL:
    case AST_NODE_NUMBER_LITERAL:
    case AST_NODE_UNREACHABLE_LITERAL:
    case AST_NODE_ASM_SIMPLE:
    case AST_NODE_ASM:
    case AST_NODE_ASM_LEGACY:
    case AST_NODE_ENUM_LITERAL:
    case AST_NODE_ERROR_VALUE:
    case AST_NODE_ANYFRAME_LITERAL:
    case AST_NODE_CONTINUE:
    case AST_NODE_CHAR_LITERAL:
    case AST_NODE_ERROR_SET_DECL:
        return false;

    // builtin_call (AstRlAnnotate.zig:322-330).
    case AST_NODE_BUILTIN_CALL_TWO:
    case AST_NODE_BUILTIN_CALL_TWO_COMMA: {
        uint32_t args[2];
        uint32_t nargs = 0;
        if (nd.lhs != 0)
            args[nargs++] = nd.lhs;
        if (nd.rhs != 0)
            args[nargs++] = nd.rhs;
        return rlBuiltinCall(ag, block, node, args, nargs);
    }
    case AST_NODE_BUILTIN_CALL:
    case AST_NODE_BUILTIN_CALL_COMMA: {
        uint32_t start = nd.lhs;
        uint32_t end = nd.rhs;
        return rlBuiltinCall(
            ag, block, node, tree->extra_data.arr + start, end - start);
    }

    // call (AstRlAnnotate.zig:332-351).
    case AST_NODE_CALL_ONE:
    case AST_NODE_CALL_ONE_COMMA: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        if (nd.rhs != 0)
            (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    }
    case AST_NODE_CALL:
    case AST_NODE_CALL_COMMA: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        uint32_t start = tree->extra_data.arr[nd.rhs];
        uint32_t end = tree->extra_data.arr[nd.rhs + 1];
        for (uint32_t i = start; i < end; i++)
            (void)rlExpr(ag, tree->extra_data.arr[i], block, RL_RI_TYPE_ONLY);
        return false;
    }

    // return (AstRlAnnotate.zig:353-361).
    case AST_NODE_RETURN:
        if (nd.lhs != 0) {
            bool ret_consumes_rl = rlExpr(ag, nd.lhs, block, RL_RI_TYPED_PTR);
            if (ret_consumes_rl)
                nodesNeedRlAdd(ag, node);
        }
        return false;

    // field_access (AstRlAnnotate.zig:363-367).
    case AST_NODE_FIELD_ACCESS:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // if_simple, if (AstRlAnnotate.zig:369-387).
    case AST_NODE_IF_SIMPLE:
    case AST_NODE_IF: {
        uint32_t cond_node = nd.lhs;
        uint32_t then_node, else_node = 0;
        if (tag == AST_NODE_IF_SIMPLE) {
            then_node = nd.rhs;
        } else {
            then_node = tree->extra_data.arr[nd.rhs];
            else_node = tree->extra_data.arr[nd.rhs + 1];
        }
        // Detect payload/error token.
        uint32_t last_cond_tok = lastToken(tree, cond_node);
        uint32_t pipe_tok = last_cond_tok + 2;
        bool has_payload = (pipe_tok < tree->tokens.len
            && tree->tokens.tags[pipe_tok] == TOKEN_PIPE);
        bool has_error = false;
        if (else_node != 0) {
            uint32_t else_tok = lastToken(tree, then_node) + 1;
            has_error = (else_tok + 1 < tree->tokens.len
                && tree->tokens.tags[else_tok + 1] == TOKEN_PIPE);
        }
        if (has_error || has_payload)
            (void)rlExpr(ag, cond_node, block, RL_RI_NONE);
        else
            (void)rlExpr(ag, cond_node, block, RL_RI_TYPE_ONLY);

        if (else_node != 0) {
            bool then_uses = rlExpr(ag, then_node, block, ri);
            bool else_uses = rlExpr(ag, else_node, block, ri);
            bool uses_rl = then_uses || else_uses;
            if (uses_rl)
                nodesNeedRlAdd(ag, node);
            return uses_rl;
        } else {
            (void)rlExpr(ag, then_node, block, RL_RI_NONE);
            return false;
        }
    }

    // while (AstRlAnnotate.zig:389-419).
    case AST_NODE_WHILE_SIMPLE:
    case AST_NODE_WHILE_CONT:
    case AST_NODE_WHILE: {
        uint32_t cond_node = nd.lhs;
        uint32_t body_node, cont_node = 0, else_node = 0;
        if (tag == AST_NODE_WHILE_SIMPLE) {
            body_node = nd.rhs;
        } else if (tag == AST_NODE_WHILE_CONT) {
            cont_node = tree->extra_data.arr[nd.rhs];
            body_node = tree->extra_data.arr[nd.rhs + 1];
        } else {
            cont_node = tree->extra_data.arr[nd.rhs];
            body_node = tree->extra_data.arr[nd.rhs + 1];
            else_node = tree->extra_data.arr[nd.rhs + 2];
        }
        uint32_t main_tok = tree->nodes.main_tokens[node];
        uint32_t tok_i = main_tok;
        if (tok_i >= 1 && tree->tokens.tags[tok_i - 1] == TOKEN_KEYWORD_INLINE)
            tok_i = tok_i - 1;
        bool is_labeled
            = (tok_i >= 2 && tree->tokens.tags[tok_i - 1] == TOKEN_COLON
                && tree->tokens.tags[tok_i - 2] == TOKEN_IDENTIFIER);
        uint32_t label_token = is_labeled ? tok_i - 2 : UINT32_MAX;

        // Detect payload/error.
        uint32_t last_cond_tok = lastToken(tree, cond_node);
        uint32_t pipe_tok = last_cond_tok + 2;
        bool has_payload = (pipe_tok < tree->tokens.len
            && tree->tokens.tags[pipe_tok] == TOKEN_PIPE);
        // Error token detection for while: check for else |err|.
        bool has_error = false;
        if (else_node != 0) {
            uint32_t else_tok = lastToken(tree, body_node) + 1;
            has_error = (else_tok + 1 < tree->tokens.len
                && tree->tokens.tags[else_tok + 1] == TOKEN_PIPE);
        }
        if (has_error || has_payload)
            (void)rlExpr(ag, cond_node, block, RL_RI_NONE);
        else
            (void)rlExpr(ag, cond_node, block, RL_RI_TYPE_ONLY);

        RlBlock new_block;
        new_block.parent = block;
        new_block.label_token = label_token;
        new_block.is_loop = true;
        new_block.ri = ri;
        new_block.consumes_res_ptr = false;

        if (cont_node != 0)
            (void)rlExpr(ag, cont_node, &new_block, RL_RI_NONE);
        (void)rlExpr(ag, body_node, &new_block, RL_RI_NONE);
        bool else_consumes = false;
        if (else_node != 0)
            else_consumes = rlExpr(ag, else_node, block, ri);
        if (new_block.consumes_res_ptr || else_consumes) {
            nodesNeedRlAdd(ag, node);
            return true;
        }
        return false;
    }

    // for (AstRlAnnotate.zig:421-454).
    case AST_NODE_FOR_SIMPLE:
    case AST_NODE_FOR: {
        uint32_t input_buf[16];
        const uint32_t* inputs = NULL;
        uint32_t num_inputs = 0;
        uint32_t body_node = 0;
        uint32_t else_node = 0;

        if (tag == AST_NODE_FOR_SIMPLE) {
            input_buf[0] = nd.lhs;
            inputs = input_buf;
            num_inputs = 1;
            body_node = nd.rhs;
        } else {
            AstFor for_data;
            memcpy(&for_data, &nd.rhs, sizeof(AstFor));
            num_inputs = for_data.inputs;
            if (num_inputs > 16)
                num_inputs = 16;
            for (uint32_t i = 0; i < num_inputs; i++)
                input_buf[i] = tree->extra_data.arr[nd.lhs + i];
            inputs = input_buf;
            body_node = tree->extra_data.arr[nd.lhs + num_inputs];
            if (for_data.has_else)
                else_node = tree->extra_data.arr[nd.lhs + num_inputs + 1];
        }

        uint32_t main_tok = tree->nodes.main_tokens[node];
        uint32_t for_tok_i = main_tok;
        if (for_tok_i >= 1
            && tree->tokens.tags[for_tok_i - 1] == TOKEN_KEYWORD_INLINE)
            for_tok_i = for_tok_i - 1;
        bool is_labeled = (for_tok_i >= 2
            && tree->tokens.tags[for_tok_i - 1] == TOKEN_COLON
            && tree->tokens.tags[for_tok_i - 2] == TOKEN_IDENTIFIER);
        uint32_t label_token = is_labeled ? for_tok_i - 2 : UINT32_MAX;

        for (uint32_t i = 0; i < num_inputs; i++) {
            uint32_t input = inputs[i];
            if (tree->nodes.tags[input] == AST_NODE_FOR_RANGE) {
                AstData range_nd = tree->nodes.datas[input];
                (void)rlExpr(ag, range_nd.lhs, block, RL_RI_TYPE_ONLY);
                if (range_nd.rhs != 0)
                    (void)rlExpr(ag, range_nd.rhs, block, RL_RI_TYPE_ONLY);
            } else {
                (void)rlExpr(ag, input, block, RL_RI_NONE);
            }
        }

        RlBlock new_block;
        new_block.parent = block;
        new_block.label_token = label_token;
        new_block.is_loop = true;
        new_block.ri = ri;
        new_block.consumes_res_ptr = false;

        (void)rlExpr(ag, body_node, &new_block, RL_RI_NONE);
        bool else_consumes = false;
        if (else_node != 0)
            else_consumes = rlExpr(ag, else_node, block, ri);
        if (new_block.consumes_res_ptr || else_consumes) {
            nodesNeedRlAdd(ag, node);
            return true;
        }
        return false;
    }

    // slice (AstRlAnnotate.zig:456-480).
    case AST_NODE_SLICE_OPEN:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    case AST_NODE_SLICE: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        uint32_t start = tree->extra_data.arr[nd.rhs];
        uint32_t end = tree->extra_data.arr[nd.rhs + 1];
        (void)rlExpr(ag, start, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, end, block, RL_RI_TYPE_ONLY);
        return false;
    }
    case AST_NODE_SLICE_SENTINEL: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        AstSliceSentinel ss;
        ss.start = tree->extra_data.arr[nd.rhs];
        ss.end = tree->extra_data.arr[nd.rhs + 1];
        ss.sentinel = tree->extra_data.arr[nd.rhs + 2];
        (void)rlExpr(ag, ss.start, block, RL_RI_TYPE_ONLY);
        if (ss.end != 0)
            (void)rlExpr(ag, ss.end, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, ss.sentinel, block, RL_RI_NONE);
        return false;
    }

    // deref (AstRlAnnotate.zig:481-484).
    case AST_NODE_DEREF:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // address_of (AstRlAnnotate.zig:485-488).
    case AST_NODE_ADDRESS_OF:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // optional_type (AstRlAnnotate.zig:489-492).
    case AST_NODE_OPTIONAL_TYPE:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        return false;

    // try, nosuspend (AstRlAnnotate.zig:493-495).
    case AST_NODE_TRY:
    case AST_NODE_NOSUSPEND:
        return rlExpr(ag, nd.lhs, block, ri);

    // grouped_expression, unwrap_optional (AstRlAnnotate.zig:496-498).
    case AST_NODE_GROUPED_EXPRESSION:
    case AST_NODE_UNWRAP_OPTIONAL:
        return rlExpr(ag, nd.lhs, block, ri);

    // block (AstRlAnnotate.zig:500-508).
    case AST_NODE_BLOCK_TWO:
    case AST_NODE_BLOCK_TWO_SEMICOLON: {
        uint32_t stmts[2];
        uint32_t count = 0;
        if (nd.lhs != 0)
            stmts[count++] = nd.lhs;
        if (nd.rhs != 0)
            stmts[count++] = nd.rhs;
        return rlBlockExpr(ag, block, ri, node, stmts, count);
    }
    case AST_NODE_BLOCK:
    case AST_NODE_BLOCK_SEMICOLON:
        return rlBlockExpr(ag, block, ri, node, tree->extra_data.arr + nd.lhs,
            nd.rhs - nd.lhs);

    // anyframe_type (AstRlAnnotate.zig:509-513).
    case AST_NODE_ANYFRAME_TYPE:
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;

    // catch/orelse (AstRlAnnotate.zig:514-522).
    case AST_NODE_CATCH:
    case AST_NODE_ORELSE: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        bool rhs_consumes = rlExpr(ag, nd.rhs, block, ri);
        if (rhs_consumes)
            nodesNeedRlAdd(ag, node);
        return rhs_consumes;
    }

    // ptr_type (AstRlAnnotate.zig:524-546).
    case AST_NODE_PTR_TYPE_ALIGNED:
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    case AST_NODE_PTR_TYPE_SENTINEL:
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    case AST_NODE_PTR_TYPE: {
        const AstPtrType* pt
            = (const AstPtrType*)(tree->extra_data.arr + nd.lhs);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        if (pt->sentinel != UINT32_MAX)
            (void)rlExpr(ag, pt->sentinel, block, RL_RI_TYPE_ONLY);
        if (pt->align_node != UINT32_MAX)
            (void)rlExpr(ag, pt->align_node, block, RL_RI_TYPE_ONLY);
        if (pt->addrspace_node != UINT32_MAX)
            (void)rlExpr(ag, pt->addrspace_node, block, RL_RI_TYPE_ONLY);
        return false;
    }
    case AST_NODE_PTR_TYPE_BIT_RANGE: {
        const AstPtrTypeBitRange* pt
            = (const AstPtrTypeBitRange*)(tree->extra_data.arr + nd.lhs);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        if (pt->sentinel != UINT32_MAX)
            (void)rlExpr(ag, pt->sentinel, block, RL_RI_TYPE_ONLY);
        // align_node is always present for bit_range.
        (void)rlExpr(ag, pt->align_node, block, RL_RI_TYPE_ONLY);
        if (pt->addrspace_node != UINT32_MAX)
            (void)rlExpr(ag, pt->addrspace_node, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, pt->bit_range_start, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, pt->bit_range_end, block, RL_RI_TYPE_ONLY);
        return false;
    }

    // container_decl (AstRlAnnotate.zig:548-564).
    case AST_NODE_CONTAINER_DECL:
    case AST_NODE_CONTAINER_DECL_TRAILING:
    case AST_NODE_CONTAINER_DECL_ARG:
    case AST_NODE_CONTAINER_DECL_ARG_TRAILING:
    case AST_NODE_CONTAINER_DECL_TWO:
    case AST_NODE_CONTAINER_DECL_TWO_TRAILING:
    case AST_NODE_TAGGED_UNION:
    case AST_NODE_TAGGED_UNION_TRAILING:
    case AST_NODE_TAGGED_UNION_ENUM_TAG:
    case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING:
    case AST_NODE_TAGGED_UNION_TWO:
    case AST_NODE_TAGGED_UNION_TWO_TRAILING:
        rlContainerDecl(ag, block, node);
        return false;

    // break (AstRlAnnotate.zig:566-596).
    case AST_NODE_BREAK: {
        uint32_t opt_label_tok = nd.lhs; // 0 = no label
        uint32_t rhs_node = nd.rhs; // 0 = void break
        if (rhs_node == 0)
            return false;

        RlBlock* opt_cur_block = block;
        if (opt_label_tok != 0) {
            // Labeled break: find matching block.
            while (opt_cur_block != NULL) {
                if (opt_cur_block->label_token != UINT32_MAX
                    && rlTokenIdentEqual(
                        tree, opt_cur_block->label_token, opt_label_tok))
                    break;
                opt_cur_block = opt_cur_block->parent;
            }
        } else {
            // No label: breaking from innermost loop.
            while (opt_cur_block != NULL) {
                if (opt_cur_block->is_loop)
                    break;
                opt_cur_block = opt_cur_block->parent;
            }
        }

        if (opt_cur_block != NULL) {
            bool consumes = rlExpr(ag, rhs_node, block, opt_cur_block->ri);
            if (consumes)
                opt_cur_block->consumes_res_ptr = true;
        } else {
            (void)rlExpr(ag, rhs_node, block, RL_RI_NONE);
        }
        return false;
    }

    // array_type (AstRlAnnotate.zig:598-611).
    case AST_NODE_ARRAY_TYPE:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;
    case AST_NODE_ARRAY_TYPE_SENTINEL: {
        (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
        uint32_t elem_type = tree->extra_data.arr[nd.rhs + 1];
        uint32_t sentinel = tree->extra_data.arr[nd.rhs];
        (void)rlExpr(ag, elem_type, block, RL_RI_TYPE_ONLY);
        (void)rlExpr(ag, sentinel, block, RL_RI_TYPE_ONLY);
        return false;
    }

    // array_access (AstRlAnnotate.zig:612-617).
    case AST_NODE_ARRAY_ACCESS:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_TYPE_ONLY);
        return false;

    // comptime (AstRlAnnotate.zig:618-623).
    case AST_NODE_COMPTIME:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // switch (AstRlAnnotate.zig:624-650).
    case AST_NODE_SWITCH:
    case AST_NODE_SWITCH_COMMA: {
        uint32_t cond_node = nd.lhs;
        uint32_t extra_idx = nd.rhs;
        uint32_t cases_start = tree->extra_data.arr[extra_idx];
        uint32_t cases_end = tree->extra_data.arr[extra_idx + 1];

        (void)rlExpr(ag, cond_node, block, RL_RI_NONE);

        bool any_consumed = false;
        for (uint32_t ci = cases_start; ci < cases_end; ci++) {
            uint32_t case_node = tree->extra_data.arr[ci];
            AstNodeTag ct = tree->nodes.tags[case_node];
            AstData cd = tree->nodes.datas[case_node];

            // Process case values.
            if (ct == AST_NODE_SWITCH_CASE_ONE
                || ct == AST_NODE_SWITCH_CASE_INLINE_ONE) {
                if (cd.lhs != 0) {
                    if (tree->nodes.tags[cd.lhs] == AST_NODE_SWITCH_RANGE) {
                        AstData rd = tree->nodes.datas[cd.lhs];
                        (void)rlExpr(ag, rd.lhs, block, RL_RI_NONE);
                        (void)rlExpr(ag, rd.rhs, block, RL_RI_NONE);
                    } else {
                        (void)rlExpr(ag, cd.lhs, block, RL_RI_NONE);
                    }
                }
            } else {
                // SWITCH_CASE / SWITCH_CASE_INLINE: SubRange[lhs]
                uint32_t items_start = tree->extra_data.arr[cd.lhs];
                uint32_t items_end = tree->extra_data.arr[cd.lhs + 1];
                for (uint32_t ii = items_start; ii < items_end; ii++) {
                    uint32_t item = tree->extra_data.arr[ii];
                    if (tree->nodes.tags[item] == AST_NODE_SWITCH_RANGE) {
                        AstData rd = tree->nodes.datas[item];
                        (void)rlExpr(ag, rd.lhs, block, RL_RI_NONE);
                        (void)rlExpr(ag, rd.rhs, block, RL_RI_NONE);
                    } else {
                        (void)rlExpr(ag, item, block, RL_RI_NONE);
                    }
                }
            }
            // Process case target expr.
            if (rlExpr(ag, cd.rhs, block, ri))
                any_consumed = true;
        }
        if (any_consumed)
            nodesNeedRlAdd(ag, node);
        return any_consumed;
    }

    // suspend (AstRlAnnotate.zig:651-654).
    case AST_NODE_SUSPEND:
        if (nd.lhs != 0)
            (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // resume (AstRlAnnotate.zig:655-658).
    case AST_NODE_RESUME:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;

    // array_init (AstRlAnnotate.zig:660-695).
    case AST_NODE_ARRAY_INIT_ONE:
    case AST_NODE_ARRAY_INIT_ONE_COMMA:
    case AST_NODE_ARRAY_INIT_DOT_TWO:
    case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA:
    case AST_NODE_ARRAY_INIT_DOT:
    case AST_NODE_ARRAY_INIT_DOT_COMMA:
    case AST_NODE_ARRAY_INIT:
    case AST_NODE_ARRAY_INIT_COMMA: {
        // Extract type_expr and elements.
        uint32_t type_expr = 0;
        uint32_t elem_buf[2];
        const uint32_t* elems = NULL;
        uint32_t nelem = 0;
        switch (tag) {
        case AST_NODE_ARRAY_INIT_ONE:
        case AST_NODE_ARRAY_INIT_ONE_COMMA:
            type_expr = nd.lhs;
            if (nd.rhs != 0) {
                elem_buf[0] = nd.rhs;
                elems = elem_buf;
                nelem = 1;
            }
            break;
        case AST_NODE_ARRAY_INIT_DOT_TWO:
        case AST_NODE_ARRAY_INIT_DOT_TWO_COMMA: {
            uint32_t idx = 0;
            if (nd.lhs != 0)
                elem_buf[idx++] = nd.lhs;
            if (nd.rhs != 0)
                elem_buf[idx++] = nd.rhs;
            elems = elem_buf;
            nelem = idx;
            break;
        }
        case AST_NODE_ARRAY_INIT_DOT:
        case AST_NODE_ARRAY_INIT_DOT_COMMA:
            elems = tree->extra_data.arr + nd.lhs;
            nelem = nd.rhs - nd.lhs;
            break;
        case AST_NODE_ARRAY_INIT:
        case AST_NODE_ARRAY_INIT_COMMA: {
            type_expr = nd.lhs;
            uint32_t start = tree->extra_data.arr[nd.rhs];
            uint32_t end = tree->extra_data.arr[nd.rhs + 1];
            elems = tree->extra_data.arr + start;
            nelem = end - start;
            break;
        }
        default:
            break;
        }
        if (type_expr != 0) {
            (void)rlExpr(ag, type_expr, block, RL_RI_NONE);
            for (uint32_t i = 0; i < nelem; i++)
                (void)rlExpr(ag, elems[i], block, RL_RI_TYPE_ONLY);
            return false;
        }
        if (ri.have_type) {
            for (uint32_t i = 0; i < nelem; i++)
                (void)rlExpr(ag, elems[i], block, ri);
            return ri.have_ptr;
        } else {
            for (uint32_t i = 0; i < nelem; i++)
                (void)rlExpr(ag, elems[i], block, RL_RI_NONE);
            return false;
        }
    }

    // struct_init (AstRlAnnotate.zig:697-732).
    case AST_NODE_STRUCT_INIT_ONE:
    case AST_NODE_STRUCT_INIT_ONE_COMMA:
    case AST_NODE_STRUCT_INIT_DOT_TWO:
    case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA:
    case AST_NODE_STRUCT_INIT_DOT:
    case AST_NODE_STRUCT_INIT_DOT_COMMA:
    case AST_NODE_STRUCT_INIT:
    case AST_NODE_STRUCT_INIT_COMMA: {
        uint32_t type_expr = 0;
        uint32_t field_buf[2];
        const uint32_t* fields = NULL;
        uint32_t nfields = 0;
        switch (tag) {
        case AST_NODE_STRUCT_INIT_ONE:
        case AST_NODE_STRUCT_INIT_ONE_COMMA:
            type_expr = nd.lhs;
            if (nd.rhs != 0) {
                field_buf[0] = nd.rhs;
                fields = field_buf;
                nfields = 1;
            }
            break;
        case AST_NODE_STRUCT_INIT_DOT_TWO:
        case AST_NODE_STRUCT_INIT_DOT_TWO_COMMA: {
            uint32_t idx = 0;
            if (nd.lhs != 0)
                field_buf[idx++] = nd.lhs;
            if (nd.rhs != 0)
                field_buf[idx++] = nd.rhs;
            fields = field_buf;
            nfields = idx;
            break;
        }
        case AST_NODE_STRUCT_INIT_DOT:
        case AST_NODE_STRUCT_INIT_DOT_COMMA:
            fields = tree->extra_data.arr + nd.lhs;
            nfields = nd.rhs - nd.lhs;
            break;
        case AST_NODE_STRUCT_INIT:
        case AST_NODE_STRUCT_INIT_COMMA: {
            type_expr = nd.lhs;
            uint32_t start = tree->extra_data.arr[nd.rhs];
            uint32_t end = tree->extra_data.arr[nd.rhs + 1];
            fields = tree->extra_data.arr + start;
            nfields = end - start;
            break;
        }
        default:
            break;
        }
        if (type_expr != 0) {
            (void)rlExpr(ag, type_expr, block, RL_RI_NONE);
            for (uint32_t i = 0; i < nfields; i++)
                (void)rlExpr(ag, fields[i], block, RL_RI_TYPE_ONLY);
            return false;
        }
        if (ri.have_type) {
            for (uint32_t i = 0; i < nfields; i++)
                (void)rlExpr(ag, fields[i], block, ri);
            return ri.have_ptr;
        } else {
            for (uint32_t i = 0; i < nfields; i++)
                (void)rlExpr(ag, fields[i], block, RL_RI_NONE);
            return false;
        }
    }

    // fn_proto, fn_decl (AstRlAnnotate.zig:734-770).
    case AST_NODE_FN_PROTO_SIMPLE:
    case AST_NODE_FN_PROTO_MULTI:
    case AST_NODE_FN_PROTO_ONE:
    case AST_NODE_FN_PROTO:
    case AST_NODE_FN_DECL: {
        // Extract return type and body.
        uint32_t return_type = 0;
        uint32_t body_node = 0;

        if (tag == AST_NODE_FN_DECL) {
            body_node = nd.rhs;
            // fn_proto is nd.lhs
            uint32_t proto = nd.lhs;
            AstNodeTag ptag = tree->nodes.tags[proto];
            AstData pnd = tree->nodes.datas[proto];
            if (ptag == AST_NODE_FN_PROTO_SIMPLE) {
                return_type = pnd.rhs;
                if (pnd.lhs != 0)
                    (void)rlExpr(ag, pnd.lhs, block, RL_RI_TYPE_ONLY);
            } else if (ptag == AST_NODE_FN_PROTO_MULTI) {
                return_type = pnd.rhs;
                uint32_t ps = tree->extra_data.arr[pnd.lhs];
                uint32_t pe = tree->extra_data.arr[pnd.lhs + 1];
                for (uint32_t i = ps; i < pe; i++)
                    (void)rlExpr(
                        ag, tree->extra_data.arr[i], block, RL_RI_TYPE_ONLY);
            } else if (ptag == AST_NODE_FN_PROTO_ONE) {
                return_type = pnd.rhs;
                AstFnProtoOne fp;
                fp.param = tree->extra_data.arr[pnd.lhs];
                fp.align_expr = tree->extra_data.arr[pnd.lhs + 1];
                fp.addrspace_expr = tree->extra_data.arr[pnd.lhs + 2];
                fp.section_expr = tree->extra_data.arr[pnd.lhs + 3];
                fp.callconv_expr = tree->extra_data.arr[pnd.lhs + 4];
                if (fp.param != 0)
                    (void)rlExpr(ag, fp.param, block, RL_RI_TYPE_ONLY);
                if (fp.align_expr != 0)
                    (void)rlExpr(ag, fp.align_expr, block, RL_RI_TYPE_ONLY);
                if (fp.addrspace_expr != 0)
                    (void)rlExpr(
                        ag, fp.addrspace_expr, block, RL_RI_TYPE_ONLY);
                if (fp.section_expr != 0)
                    (void)rlExpr(ag, fp.section_expr, block, RL_RI_TYPE_ONLY);
                if (fp.callconv_expr != 0)
                    (void)rlExpr(ag, fp.callconv_expr, block, RL_RI_TYPE_ONLY);
            } else if (ptag == AST_NODE_FN_PROTO) {
                return_type = pnd.rhs;
                AstFnProto fp;
                fp.params_start = tree->extra_data.arr[pnd.lhs];
                fp.params_end = tree->extra_data.arr[pnd.lhs + 1];
                fp.align_expr = tree->extra_data.arr[pnd.lhs + 2];
                fp.addrspace_expr = tree->extra_data.arr[pnd.lhs + 3];
                fp.section_expr = tree->extra_data.arr[pnd.lhs + 4];
                fp.callconv_expr = tree->extra_data.arr[pnd.lhs + 5];
                for (uint32_t i = fp.params_start; i < fp.params_end; i++)
                    (void)rlExpr(
                        ag, tree->extra_data.arr[i], block, RL_RI_TYPE_ONLY);
                if (fp.align_expr != 0)
                    (void)rlExpr(ag, fp.align_expr, block, RL_RI_TYPE_ONLY);
                if (fp.addrspace_expr != 0)
                    (void)rlExpr(
                        ag, fp.addrspace_expr, block, RL_RI_TYPE_ONLY);
                if (fp.section_expr != 0)
                    (void)rlExpr(ag, fp.section_expr, block, RL_RI_TYPE_ONLY);
                if (fp.callconv_expr != 0)
                    (void)rlExpr(ag, fp.callconv_expr, block, RL_RI_TYPE_ONLY);
            }
        } else {
            // Standalone fn_proto (no body).
            if (tag == AST_NODE_FN_PROTO_SIMPLE) {
                return_type = nd.rhs;
                if (nd.lhs != 0)
                    (void)rlExpr(ag, nd.lhs, block, RL_RI_TYPE_ONLY);
            } else if (tag == AST_NODE_FN_PROTO_MULTI) {
                return_type = nd.rhs;
                uint32_t ps = tree->extra_data.arr[nd.lhs];
                uint32_t pe = tree->extra_data.arr[nd.lhs + 1];
                for (uint32_t i = ps; i < pe; i++)
                    (void)rlExpr(
                        ag, tree->extra_data.arr[i], block, RL_RI_TYPE_ONLY);
            } else if (tag == AST_NODE_FN_PROTO_ONE) {
                return_type = nd.rhs;
                AstFnProtoOne fp;
                fp.param = tree->extra_data.arr[nd.lhs];
                fp.align_expr = tree->extra_data.arr[nd.lhs + 1];
                fp.addrspace_expr = tree->extra_data.arr[nd.lhs + 2];
                fp.section_expr = tree->extra_data.arr[nd.lhs + 3];
                fp.callconv_expr = tree->extra_data.arr[nd.lhs + 4];
                if (fp.param != 0)
                    (void)rlExpr(ag, fp.param, block, RL_RI_TYPE_ONLY);
                if (fp.align_expr != 0)
                    (void)rlExpr(ag, fp.align_expr, block, RL_RI_TYPE_ONLY);
                if (fp.addrspace_expr != 0)
                    (void)rlExpr(
                        ag, fp.addrspace_expr, block, RL_RI_TYPE_ONLY);
                if (fp.section_expr != 0)
                    (void)rlExpr(ag, fp.section_expr, block, RL_RI_TYPE_ONLY);
                if (fp.callconv_expr != 0)
                    (void)rlExpr(ag, fp.callconv_expr, block, RL_RI_TYPE_ONLY);
            } else if (tag == AST_NODE_FN_PROTO) {
                return_type = nd.rhs;
                AstFnProto fp;
                fp.params_start = tree->extra_data.arr[nd.lhs];
                fp.params_end = tree->extra_data.arr[nd.lhs + 1];
                fp.align_expr = tree->extra_data.arr[nd.lhs + 2];
                fp.addrspace_expr = tree->extra_data.arr[nd.lhs + 3];
                fp.section_expr = tree->extra_data.arr[nd.lhs + 4];
                fp.callconv_expr = tree->extra_data.arr[nd.lhs + 5];
                for (uint32_t i = fp.params_start; i < fp.params_end; i++)
                    (void)rlExpr(
                        ag, tree->extra_data.arr[i], block, RL_RI_TYPE_ONLY);
                if (fp.align_expr != 0)
                    (void)rlExpr(ag, fp.align_expr, block, RL_RI_TYPE_ONLY);
                if (fp.addrspace_expr != 0)
                    (void)rlExpr(
                        ag, fp.addrspace_expr, block, RL_RI_TYPE_ONLY);
                if (fp.section_expr != 0)
                    (void)rlExpr(ag, fp.section_expr, block, RL_RI_TYPE_ONLY);
                if (fp.callconv_expr != 0)
                    (void)rlExpr(ag, fp.callconv_expr, block, RL_RI_TYPE_ONLY);
            }
        }

        if (return_type != 0)
            (void)rlExpr(ag, return_type, block, RL_RI_TYPE_ONLY);
        if (body_node != 0)
            (void)rlExpr(ag, body_node, block, RL_RI_NONE);
        return false;
    }

    // Remaining: usingnamespace, await, assign_destructure, async calls.
    case AST_NODE_USINGNAMESPACE:
        return false;
    case AST_NODE_AWAIT:
        (void)rlExpr(ag, nd.lhs, block, RL_RI_NONE);
        return false;
    case AST_NODE_ASSIGN_DESTRUCTURE: {
        uint32_t extra_start = nd.lhs;
        uint32_t variable_count = tree->extra_data.arr[extra_start];
        for (uint32_t i = 0; i < variable_count; i++)
            (void)rlExpr(ag, tree->extra_data.arr[extra_start + 1 + i], block,
                RL_RI_NONE);
        (void)rlExpr(ag, nd.rhs, block, RL_RI_NONE);
        return false;
    }
    case AST_NODE_ASYNC_CALL_ONE:
    case AST_NODE_ASYNC_CALL_ONE_COMMA:
    case AST_NODE_ASYNC_CALL:
    case AST_NODE_ASYNC_CALL_COMMA:
        return false; // async not relevant

    default:
        return false;
    }
}

// astRlAnnotate (AstRlAnnotate.zig:64-83).
// Entry point: run the RL annotation pre-pass.
static void astRlAnnotate(AstGenCtx* ag) {
    const Ast* tree = ag->tree;
    if (tree->has_error)
        return;

    // Get root container members (same as in astGen).
    AstData root_data = tree->nodes.datas[0];
    uint32_t members_start = root_data.lhs;
    uint32_t members_end = root_data.rhs;
    const uint32_t* members = tree->extra_data.arr + members_start;
    uint32_t members_len = members_end - members_start;

    for (uint32_t i = 0; i < members_len; i++)
        (void)rlExpr(ag, members[i], NULL, RL_RI_NONE);
}

// --- Public API: astGen (AstGen.zig:144) ---

Zir astGen(const Ast* ast) {
    AstGenCtx ag;
    memset(&ag, 0, sizeof(ag));
    ag.tree = ast;

    // Initial allocations (AstGen.zig:162-172).
    uint32_t nodes_len = ast->nodes.len;
    uint32_t init_cap = nodes_len > 8 ? nodes_len : 8;

    ag.inst_cap = init_cap;
    ag.inst_tags = ARR_INIT(ZirInstTag, ag.inst_cap);
    ag.inst_datas = ARR_INIT(ZirInstData, ag.inst_cap);

    ag.extra_cap = init_cap + ZIR_EXTRA_RESERVED_COUNT;
    ag.extra = ARR_INIT(uint32_t, ag.extra_cap);

    ag.string_bytes_cap = 16;
    ag.string_bytes = ARR_INIT(uint8_t, ag.string_bytes_cap);

    // String table index 0 is reserved for NullTerminatedString.empty
    // (AstGen.zig:163).
    ag.string_bytes[0] = 0;
    ag.string_bytes_len = 1;

    // Reserve extra[0..1] (AstGen.zig:170-172).
    ag.extra[ZIR_EXTRA_COMPILE_ERRORS] = 0;
    ag.extra[ZIR_EXTRA_IMPORTS] = 0;
    ag.extra_len = ZIR_EXTRA_RESERVED_COUNT;

    // Run AstRlAnnotate pre-pass (AstGen.zig:150-151).
    astRlAnnotate(&ag);

    // Set up root GenZir scope (AstGen.zig:176-185).
    GenZir gen_scope;
    memset(&gen_scope, 0, sizeof(gen_scope));
    gen_scope.base.tag = SCOPE_GEN_ZIR;
    gen_scope.parent = NULL;
    gen_scope.astgen = &ag;
    gen_scope.is_comptime = true;
    gen_scope.decl_node_index = 0; // root
    gen_scope.decl_line = 0;
    gen_scope.break_block = UINT32_MAX;
    gen_scope.any_defer_node = UINT32_MAX;

    // Get root container members: containerDeclRoot (AstGen.zig:191-195).
    AstData root_data = ast->nodes.datas[0];
    uint32_t members_start = root_data.lhs;
    uint32_t members_end = root_data.rhs;
    const uint32_t* members = ast->extra_data.arr + members_start;
    uint32_t members_len = members_end - members_start;

    structDeclInner(
        &ag, &gen_scope, 0, members, members_len, 0, 0, 0 /* parent */);

    // Write imports list (AstGen.zig:227-244).
    writeImports(&ag);

    // Build output Zir (AstGen.zig:211-239).
    Zir zir;
    zir.inst_len = ag.inst_len;
    zir.inst_cap = ag.inst_cap;
    zir.inst_tags = ag.inst_tags;
    zir.inst_datas = ag.inst_datas;
    zir.extra_len = ag.extra_len;
    zir.extra_cap = ag.extra_cap;
    zir.extra = ag.extra;
    zir.string_bytes_len = ag.string_bytes_len;
    zir.string_bytes_cap = ag.string_bytes_cap;
    zir.string_bytes = ag.string_bytes;
    zir.has_compile_errors = ag.has_compile_errors;

    free(ag.imports);
    free(ag.scratch_instructions);
    free(ag.scratch_extra);
    free(ag.ref_table_keys);
    free(ag.ref_table_vals);
    free(ag.nodes_need_rl);
    free(ag.string_table);

    return zir;
}