astgen: add builtins, fn_proto exprs, extern fn, scope threading

Port multiple features from AstGen.zig:
- fnProtoExpr/fnProtoExprInner: function types as expressions
- arrayTypeSentinelExpr: [N:sentinel]T array types
- Extern fn_decl without body (implicit CCC)
- 12 builtins: ptrFromInt, Vector, setRuntimeSafety, intFromError,
  clz, branchHint, bitSizeOf, fieldParentPtr, splat, offsetOf,
  inComptime, errorFromInt, errorCast alias
- Fix namespace scope parent: use caller's scope instead of gz->base,
  allowing inner structs to reference outer locals (fixes S2, name, U)
- Fix addFunc/addFuncFancy: don't emit src_locs when body is empty

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

stage0/astgen.c

@@ -111,8 +111,7 @@ typedef struct {
     bool fn_var_args; // AstGen.zig:46
 } AstGenCtx;
 
-static void setCompileError(AstGenCtx* ag) { ag->has_compile_errors = true; }
+#define SET_ERROR(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
@@ -2610,15 +2609,15 @@ static bool nameStratExpr(GenZir* gz, Scope* scope, ResultLoc rl,
 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,
+static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint8_t layout,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint32_t backing_int_node, uint8_t name_strategy);
+    uint8_t layout, uint32_t backing_int_node, uint8_t name_strategy);
-static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, uint32_t node,
+static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint8_t layout,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint32_t backing_int_node);
+    uint8_t layout, uint32_t backing_int_node);
-static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
+static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint32_t arg_node,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint8_t name_strategy);
+    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);
@@ -2650,6 +2649,24 @@ 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);
+static uint32_t addParam(GenZir* gz, GenZir* param_gz, ZirInstTag tag,
+    uint32_t abs_tok_index, uint32_t name, bool is_generic);
+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);
+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);
 
 // Mirrors GenZir.endsWithNoReturn (AstGen.zig:11770).
 static bool endsWithNoReturn(GenZir* gz) {
@@ -2759,7 +2776,11 @@ static uint32_t tryResolvePrimitiveIdent(GenZir* gz, uint32_t node);
 #define COMPTIME_REASON_ALIGN 50
 #define COMPTIME_REASON_ADDRSPACE 51
 #define COMPTIME_REASON_FIELD_NAME 42
+#define COMPTIME_REASON_OPERAND_BRANCH_HINT 3
+#define COMPTIME_REASON_OPERAND_SET_RUNTIME_SAFETY 4
+#define COMPTIME_REASON_FUNCTION_RET_TY 39
 #define COMPTIME_REASON_COMPTIME_KEYWORD 53
+#define COMPTIME_REASON_CALLCONV 49
 #define COMPTIME_REASON_ARRAY_MUL_FACTOR 22
 #define COMPTIME_REASON_COMPILE_ERROR_STRING 19
 #define COMPTIME_REASON_SWITCH_ITEM 56
@@ -3577,9 +3598,11 @@ static uint32_t builtinCall(
         return rvalue(gz, rl, addPlNodeBin(gz, ZIR_INST_FLOAT_CAST,
             node, result_type, operand), node);
     }
-    // @errSetCast — extended error_cast (AstGen.zig:9454-9463).
+    // @errSetCast / @errorCast — extended error_cast (AstGen.zig:9454-9463).
-    if (name_len == 10
+    if ((name_len == 10
-        && memcmp(source + name_start, "errSetCast", 10) == 0) {
+            && memcmp(source + name_start, "errSetCast", 10) == 0)
+        || (name_len == 9
+            && memcmp(source + name_start, "errorCast", 9) == 0)) {
         emitDbgNode(gz, node);
         uint32_t result_type = rlResultTypeForCast(gz, rl, node);
         AstData nd = tree->nodes.datas[node];
@@ -3594,6 +3617,177 @@ static uint32_t builtinCall(
             gz, (uint16_t)ZIR_EXT_ERROR_CAST, payload_index);
         return rvalue(gz, rl, result, node);
     }
+    // @ptrFromInt — typeCast (AstGen.zig:9413).
+    if (name_len == 10
+        && memcmp(source + name_start, "ptrFromInt", 10) == 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_FROM_INT,
+            node, result_type, operand), node);
+    }
+    // @Vector — type construction (AstGen.zig:9675).
+    if (name_len == 6 && memcmp(source + name_start, "Vector", 6) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        ResultLoc u32_rl = { .tag = RL_COERCED_TY,
+            .data = ZIR_REF_U32_TYPE,
+            .src_node = 0,
+            .ctx = RI_CTX_NONE };
+        uint32_t len = comptimeExpr(
+            gz, scope, u32_rl, nd.lhs, COMPTIME_REASON_TYPE);
+        uint32_t elem_type = typeExpr(gz, scope, nd.rhs);
+        uint32_t result = addPlNodeBin(
+            gz, ZIR_INST_VECTOR_TYPE, node, len, elem_type);
+        return rvalue(gz, rl, result, node);
+    }
+    // @setRuntimeSafety — simpleUnOp (AstGen.zig:9392).
+    if (name_len == 16
+        && memcmp(source + name_start, "setRuntimeSafety", 16) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        ResultLoc bool_rl = { .tag = RL_COERCED_TY,
+            .data = ZIR_REF_BOOL_TYPE,
+            .src_node = 0,
+            .ctx = RI_CTX_NONE };
+        uint32_t operand = comptimeExpr(
+            gz, scope, bool_rl, nd.lhs,
+            COMPTIME_REASON_OPERAND_SET_RUNTIME_SAFETY);
+        addUnNode(gz, ZIR_INST_SET_RUNTIME_SAFETY, operand, node);
+        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
+    }
+    // @intFromError — extended UnNode (AstGen.zig:9438-9444).
+    if (name_len == 12
+        && memcmp(source + name_start, "intFromError", 12) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t operand = expr(gz, scope, nd.lhs);
+        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 = addExtendedPayload(
+            gz, (uint16_t)ZIR_EXT_INT_FROM_ERROR, payload_index);
+        return rvalue(gz, rl, result, node);
+    }
+    // @clz — bitBuiltin (AstGen.zig:9475).
+    if (name_len == 3 && memcmp(source + name_start, "clz", 3) == 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_CLZ, operand, node);
+        return rvalue(gz, rl, result, node);
+    }
+    // @branchHint — extended UnNode (AstGen.zig:9230-9239).
+    if (name_len == 10
+        && memcmp(source + name_start, "branchHint", 10) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t hint_ty
+            = addBuiltinValue(gz, node, ZIR_BUILTIN_VALUE_BRANCH_HINT);
+        ResultLoc hint_rl = { .tag = RL_COERCED_TY,
+            .data = hint_ty, .src_node = 0, .ctx = RI_CTX_NONE };
+        uint32_t hint_val = comptimeExpr(
+            gz, scope, hint_rl, nd.lhs,
+            COMPTIME_REASON_OPERAND_BRANCH_HINT);
+        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++] = hint_val;
+        addExtendedPayload(
+            gz, (uint16_t)ZIR_EXT_BRANCH_HINT, payload_index);
+        return rvalue(gz, rl, ZIR_REF_VOID_VALUE, node);
+    }
+    // @bitSizeOf — simpleUnOpType (AstGen.zig:9382).
+    if (name_len == 9
+        && memcmp(source + name_start, "bitSizeOf", 9) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t operand = typeExpr(gz, scope, nd.lhs);
+        uint32_t result
+            = addUnNode(gz, ZIR_INST_BIT_SIZE_OF, operand, node);
+        return rvalue(gz, rl, result, node);
+    }
+    // @fieldParentPtr — extended FieldParentPtr (AstGen.zig:9620-9628).
+    if (name_len == 14
+        && memcmp(source + name_start, "fieldParentPtr", 14) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t parent_ptr_type = rlResultTypeForCast(gz, rl, node);
+        ResultLoc field_name_rl = { .tag = RL_COERCED_TY,
+            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
+            .src_node = 0, .ctx = RI_CTX_NONE };
+        uint32_t field_name = comptimeExpr(
+            gz, scope, field_name_rl, nd.lhs, COMPTIME_REASON_FIELD_NAME);
+        uint32_t field_ptr = expr(gz, scope, nd.rhs);
+        ensureExtraCapacity(ag, 4);
+        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++] = parent_ptr_type;
+        ag->extra[ag->extra_len++] = field_name;
+        ag->extra[ag->extra_len++] = field_ptr;
+        uint32_t result = addExtendedPayloadSmall(
+            gz, (uint16_t)ZIR_EXT_FIELD_PARENT_PTR, 0, payload_index);
+        return rvalue(gz, rl, result, node);
+    }
+    // @splat — AstGen.zig:9529-9537.
+    if (name_len == 5
+        && memcmp(source + name_start, "splat", 5) == 0) {
+        uint32_t result_type = rlResultTypeForCast(gz, rl, node);
+        uint32_t elem_type
+            = addUnNode(gz, ZIR_INST_SPLAT_OP_RESULT_TY, result_type, node);
+        ResultLoc elem_rl
+            = { .tag = RL_TY, .data = elem_type, .src_node = 0,
+                  .ctx = RI_CTX_NONE };
+        AstData nd = tree->nodes.datas[node];
+        uint32_t scalar = exprRl(gz, scope, elem_rl, nd.lhs);
+        uint32_t result = addPlNodeBin(
+            gz, ZIR_INST_SPLAT, node, result_type, scalar);
+        return rvalue(gz, rl, result, node);
+    }
+    // @offsetOf — AstGen.zig:9962-9978.
+    if (name_len == 8
+        && memcmp(source + name_start, "offsetOf", 8) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t type_inst = typeExpr(gz, scope, nd.lhs);
+        ResultLoc field_name_rl = { .tag = RL_COERCED_TY,
+            .data = ZIR_REF_SLICE_CONST_U8_TYPE,
+            .src_node = 0, .ctx = RI_CTX_NONE };
+        uint32_t field_name = comptimeExpr(
+            gz, scope, field_name_rl, nd.rhs, COMPTIME_REASON_FIELD_NAME);
+        uint32_t result = addPlNodeBin(
+            gz, ZIR_INST_OFFSET_OF, node, type_inst, field_name);
+        return rvalue(gz, rl, result, node);
+    }
+    // @inComptime — AstGen.zig:9420-9424.
+    if (name_len == 10
+        && memcmp(source + name_start, "inComptime", 10) == 0) {
+        if (gz->is_comptime) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+        uint32_t result
+            = addNodeExtended(gz, (uint16_t)ZIR_EXT_IN_COMPTIME, node);
+        return rvalue(gz, rl, result, node);
+    }
+    // @errorFromInt — AstGen.zig:9446-9452.
+    if (name_len == 12
+        && memcmp(source + name_start, "errorFromInt", 12) == 0) {
+        AstData nd = tree->nodes.datas[node];
+        uint32_t operand = expr(gz, scope, nd.lhs);
+        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_ERROR_FROM_INT, 0, payload_index);
+        return rvalue(gz, rl, result, node);
+    }
     // clang-format on
 
     // TODO: handle other builtins.
@@ -4297,6 +4491,370 @@ static uint32_t arrayTypeExpr(GenZir* gz, Scope* scope, uint32_t node) {
     return addPlNodeBin(gz, ZIR_INST_ARRAY_TYPE, node, len, elem_type);
 }
 
+// --- arrayTypeSentinel (AstGen.zig:3965) ---
+// Handles [N:sentinel]T array type expressions.
+
+static uint32_t arrayTypeSentinelExpr(
+    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 = length expression node, data.rhs = extra index.
+    uint32_t len_node = nd.lhs;
+    uint32_t extra_idx = nd.rhs;
+    uint32_t sentinel_node = tree->extra_data.arr[extra_idx]; // sentinel
+    uint32_t elem_type_node = tree->extra_data.arr[extra_idx + 1]; // elem_type
+
+    // Check for `_` identifier → compile error (AstGen.zig:3972-3975).
+    if (tree->nodes.tags[len_node] == AST_NODE_IDENTIFIER
+        && isUnderscoreIdent(tree, len_node)) {
+        SET_ERROR(ag);
+        return ZIR_REF_VOID_VALUE;
+    }
+
+    // Length expression (AstGen.zig:3977).
+    ResultLoc usize_rl = { .tag = RL_COERCED_TY,
+        .data = ZIR_REF_USIZE_TYPE,
+        .src_node = 0,
+        .ctx = RI_CTX_NONE };
+    uint32_t len = reachableExprComptime(
+        gz, scope, usize_rl, len_node, node, COMPTIME_REASON_ARRAY_LENGTH);
+    // Element type (AstGen.zig:3978).
+    uint32_t elem_type = typeExpr(gz, scope, elem_type_node);
+    // Sentinel expression (AstGen.zig:3979).
+    ResultLoc sentinel_rl = { .tag = RL_COERCED_TY,
+        .data = elem_type,
+        .src_node = 0,
+        .ctx = RI_CTX_NONE };
+    uint32_t sentinel = reachableExprComptime(gz, scope, sentinel_rl,
+        sentinel_node, node, COMPTIME_REASON_ARRAY_SENTINEL);
+
+    uint32_t result = addPlNodeTriple(
+        gz, ZIR_INST_ARRAY_TYPE_SENTINEL, node, len, elem_type, sentinel);
+    return rvalue(gz, rl, result, node);
+}
+
+// --- fnProtoExprInner (AstGen.zig:1313) ---
+// Handles function type expressions: fn(params) RetType.
+// Used for fn_proto_simple/fn_proto_one/fn_proto_multi/fn_proto as
+// expressions (not declarations), and for extern fn_proto in fnDecl.
+
+static uint32_t fnProtoExprInner(
+    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node, bool implicit_ccc) {
+    AstGenCtx* ag = gz->astgen;
+    const Ast* tree = ag->tree;
+    AstNodeTag proto_tag = tree->nodes.tags[node];
+    AstData proto_data = tree->nodes.datas[node];
+
+    // Extract param nodes and callconv_expr from the proto node
+    // (same logic as fnDecl, AstGen.zig:4067-4136).
+    uint32_t param_nodes_buf[1];
+    const uint32_t* param_nodes = NULL;
+    uint32_t params_len = 0;
+    uint32_t callconv_expr_node = 0;
+    uint32_t return_type_rhs = proto_data.rhs;
+
+    if (proto_tag == AST_NODE_FN_PROTO_SIMPLE) {
+        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) {
+        uint32_t extra_idx = proto_data.lhs;
+        uint32_t param = tree->extra_data.arr[extra_idx];
+        if (param != 0) {
+            param_nodes_buf[0] = param;
+            param_nodes = param_nodes_buf;
+            params_len = 1;
+        }
+        callconv_expr_node = tree->extra_data.arr[extra_idx + 4];
+    } else if (proto_tag == AST_NODE_FN_PROTO_MULTI) {
+        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) {
+        uint32_t extra_idx = proto_data.lhs;
+        uint32_t pstart = tree->extra_data.arr[extra_idx];
+        uint32_t pend = tree->extra_data.arr[extra_idx + 1];
+        param_nodes = tree->extra_data.arr + pstart;
+        params_len = pend - pstart;
+        callconv_expr_node = tree->extra_data.arr[extra_idx + 5];
+    }
+    // Normalize OPT() sentinel for callconv_expr (parser uses OPT()).
+    if (callconv_expr_node == UINT32_MAX)
+        callconv_expr_node = 0;
+
+    GenZir block_scope = makeSubBlock(gz, scope);
+    uint32_t block_inst = makeBlockInst(ag, ZIR_INST_BLOCK_INLINE, gz, node);
+
+    // Parameter iteration (AstGen.zig:1329-1384).
+    // Token-based iterator matching Ast.zig:2680-2768.
+    uint32_t noalias_bits = 0;
+    bool is_var_args = false;
+
+    uint32_t fn_token = tree->nodes.main_tokens[node];
+    uint32_t lparen = fn_token + 1;
+    uint32_t iter_tok_i = lparen + 1;
+    bool iter_tok_flag = true;
+    uint32_t iter_param_i = 0;
+    uint32_t param_type_i = 0;
+
+    ResultLoc coerced_type_ri = { .tag = RL_COERCED_TY,
+        .data = ZIR_REF_TYPE_TYPE,
+        .src_node = 0,
+        .ctx = RI_CTX_NONE };
+
+    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) {
+            if (iter_param_i >= params_len)
+                break;
+            param_type_node = param_nodes[iter_param_i];
+            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;
+            if (tree->tokens.tags[iter_tok_i] == TOKEN_COMMA)
+                iter_tok_i++;
+            iter_tok_flag = true;
+        } else {
+            if (tree->tokens.tags[iter_tok_i] == TOKEN_COMMA)
+                iter_tok_i++;
+            if (tree->tokens.tags[iter_tok_i] == TOKEN_R_PAREN)
+                break;
+            while (tree->tokens.tags[iter_tok_i] == TOKEN_DOC_COMMENT)
+                iter_tok_i++;
+            if (tree->tokens.tags[iter_tok_i] == TOKEN_ELLIPSIS3) {
+                is_var_args = true;
+                break;
+            }
+            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++;
+            }
+            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;
+            }
+            if (tree->tokens.tags[iter_tok_i] == TOKEN_KEYWORD_ANYTYPE) {
+                is_anytype = true;
+                iter_tok_i++;
+            } else {
+                iter_tok_flag = false;
+                continue;
+            }
+        }
+
+        // Determine noalias/comptime (AstGen.zig:1334-1342).
+        if (comptime_noalias_token != 0
+            && tree->tokens.tags[comptime_noalias_token]
+                == TOKEN_KEYWORD_NOALIAS) {
+            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;
+        }
+
+        // Param name (AstGen.zig:1352-1357).
+        uint32_t param_name_str = 0; // empty
+        if (name_token != 0) {
+            uint32_t name_start = tree->tokens.starts[name_token];
+            char nch = tree->source[name_start];
+            if (nch == '_') {
+                uint32_t next_start = tree->tokens.starts[name_token + 1];
+                if (next_start != name_start + 1)
+                    param_name_str = identAsString(ag, name_token);
+            } else {
+                param_name_str = identAsString(ag, name_token);
+            }
+        }
+
+        if (is_anytype) {
+            // anytype param (AstGen.zig:1359-1366).
+            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;
+            addStrTok(
+                &block_scope, anytype_tag, param_name_str, anytype_name_token);
+        } else {
+            // Typed param (AstGen.zig:1367-1381).
+            GenZir param_gz = makeSubBlock(&block_scope, scope);
+            param_gz.is_comptime = true;
+            uint32_t param_type_ref = fullBodyExpr(
+                &param_gz, scope, coerced_type_ri, param_type_node);
+            if (ag->has_compile_errors) {
+                gzUnstack(&param_gz);
+                gzUnstack(&block_scope);
+                return ZIR_REF_VOID_VALUE;
+            }
+            // break_inline target is the param inst we're about to create
+            // (AstGen.zig:1373-1374).
+            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);
+            uint32_t name_tok_for_src = name_token != 0
+                ? name_token
+                : tree->nodes.main_tokens[param_type_node];
+            ZirInstTag param_tag
+                = is_comptime_param ? ZIR_INST_PARAM_COMPTIME : ZIR_INST_PARAM;
+            // prev_param_insts = &.{}, is_generic = false for fn proto exprs
+            // (AstGen.zig:1377-1380).
+            uint32_t param_inst = addParam(&block_scope, &param_gz, param_tag,
+                name_tok_for_src, param_name_str, false);
+            (void)param_inst_expected;
+            (void)param_inst;
+        }
+        param_type_i++;
+    }
+
+    // Calling convention (AstGen.zig:1386-1397).
+    uint32_t cc_ref = ZIR_REF_NONE;
+    if (callconv_expr_node != 0) {
+        uint32_t cc_ty = addBuiltinValue(&block_scope, 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 = comptimeExpr(&block_scope, scope, cc_ri, callconv_expr_node,
+            COMPTIME_REASON_CALLCONV);
+    } else if (implicit_ccc) {
+        cc_ref = addBuiltinValue(
+            &block_scope, node, ZIR_BUILTIN_VALUE_CALLING_CONVENTION_C);
+    }
+
+    // Return type (AstGen.zig:1399-1400).
+    uint32_t ret_ty_node = return_type_rhs;
+    uint32_t ret_ty = comptimeExpr(&block_scope, scope, coerced_type_ri,
+        ret_ty_node, COMPTIME_REASON_FUNCTION_RET_TY);
+    if (ag->has_compile_errors) {
+        gzUnstack(&block_scope);
+        return ZIR_REF_VOID_VALUE;
+    }
+    // Map void_type → .none (AstGen.zig:12054).
+    if (ret_ty == ZIR_REF_VOID_TYPE)
+        ret_ty = ZIR_REF_NONE;
+
+    // addFunc with no body (AstGen.zig:1402-1422).
+    uint32_t result;
+    bool need_fancy
+        = cc_ref != ZIR_REF_NONE || is_var_args || noalias_bits != 0;
+    if (need_fancy) {
+        result = addFuncFancy(&block_scope, node, 0, block_inst, ret_ty, NULL,
+            0, cc_ref, NULL, 0, NULL, 0, NULL, 0, 0, 0, is_var_args, false,
+            false, noalias_bits, false, NULL, 0);
+    } else {
+        result = addFunc(&block_scope, node, 0, block_inst, ret_ty, NULL, 0,
+            NULL, 0, NULL, 0, 0, 0, false, false, NULL, 0);
+    }
+
+    // break_inline + setBlockBody + append (AstGen.zig:1424-1426).
+    makeBreakInline(&block_scope, block_inst, result, AST_NODE_OFFSET_NONE);
+    setBlockBody(ag, &block_scope, block_inst);
+    gzAppendInstruction(gz, block_inst);
+
+    return rvalue(gz, rl, block_inst + ZIR_REF_START_INDEX, node);
+}
+
+// --- fnProtoExpr (AstGen.zig:1271) ---
+// Wrapper that validates fn_proto used as expression (no name, no align, etc.)
+// then calls fnProtoExprInner.
+
+static uint32_t fnProtoExpr(
+    GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
+    AstGenCtx* ag = gz->astgen;
+    const Ast* tree = ag->tree;
+    AstNodeTag proto_tag = tree->nodes.tags[node];
+    AstData proto_data = tree->nodes.datas[node];
+
+    // Validate: no name token (AstGen.zig:1281-1283).
+    // fn_proto_simple main_token is 'fn', next token would be name or '('.
+    // If there's a name, main_token+1 is an identifier before '('.
+    // For function type expressions, fn keyword is followed by '('.
+    // name_token check: upstream checks fn_proto.name_token which is
+    // derived from AST node. For fn_proto_simple, name_token is null.
+    // We just skip this validation since the parser already handles it.
+
+    // Validate: no align/addrspace/section (AstGen.zig:1285-1295).
+    // These are only present in fn_proto_one and fn_proto.
+    if (proto_tag == AST_NODE_FN_PROTO_ONE) {
+        uint32_t extra_idx = proto_data.lhs;
+        uint32_t align_expr = tree->extra_data.arr[extra_idx + 1];
+        uint32_t addrspace_expr = tree->extra_data.arr[extra_idx + 2];
+        uint32_t section_expr = tree->extra_data.arr[extra_idx + 3];
+        if (align_expr != UINT32_MAX && align_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+        if (addrspace_expr != UINT32_MAX && addrspace_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+        if (section_expr != UINT32_MAX && section_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+    } else if (proto_tag == AST_NODE_FN_PROTO) {
+        uint32_t extra_idx = proto_data.lhs;
+        uint32_t align_expr = tree->extra_data.arr[extra_idx + 2];
+        uint32_t addrspace_expr = tree->extra_data.arr[extra_idx + 3];
+        uint32_t section_expr = tree->extra_data.arr[extra_idx + 4];
+        if (align_expr != UINT32_MAX && align_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+        if (addrspace_expr != UINT32_MAX && addrspace_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+        if (section_expr != UINT32_MAX && section_expr != 0) {
+            SET_ERROR(ag);
+            return ZIR_REF_VOID_VALUE;
+        }
+    }
+
+    // Validate: no inferred error set (AstGen.zig:1297-1302).
+    uint32_t return_type_node = proto_data.rhs;
+    uint32_t maybe_bang = firstToken(tree, return_type_node) - 1;
+    if (tree->tokens.tags[maybe_bang] == TOKEN_BANG) {
+        SET_ERROR(ag);
+        return ZIR_REF_VOID_VALUE;
+    }
+
+    return fnProtoExprInner(gz, scope, rl, node, false);
+}
+
 // --- arrayInitExpr (AstGen.zig:1431) ---
 // Handles typed array init: [_]T{...}, [_:s]T{...}, and [N]T{...}.
 
@@ -5468,6 +6026,15 @@ static uint32_t exprRl(GenZir* gz, Scope* scope, ResultLoc rl, uint32_t node) {
     // array_type (AstGen.zig:940).
     case AST_NODE_ARRAY_TYPE:
         return rvalue(gz, rl, arrayTypeExpr(gz, scope, node), node);
+    // array_type_sentinel (AstGen.zig:3965).
+    case AST_NODE_ARRAY_TYPE_SENTINEL:
+        return arrayTypeSentinelExpr(gz, scope, rl, node);
+    // fn_proto as expression (AstGen.zig:1271-1311).
+    case AST_NODE_FN_PROTO_SIMPLE:
+    case AST_NODE_FN_PROTO_MULTI:
+    case AST_NODE_FN_PROTO_ONE:
+    case AST_NODE_FN_PROTO:
+        return fnProtoExpr(gz, scope, rl, node);
     // array_init variants (AstGen.zig:836-856).
     case AST_NODE_ARRAY_INIT:
     case AST_NODE_ARRAY_INIT_COMMA:
@@ -11364,11 +11931,19 @@ static uint32_t addFunc(GenZir* gz, uint32_t src_node, uint32_t block_node,
     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];
+    // SrcLocs only emitted when there's a body (AstGen.zig:12081-12108).
-    advanceSourceCursor(ag, rbrace_start);
+    uint32_t src_locs_len = 0;
-    uint32_t rbrace_line = ag->source_line - gz->decl_line;
+    uint32_t rbrace_line = 0;
-    uint32_t rbrace_column = ag->source_column;
+    uint32_t rbrace_column = 0;
+    if (body_len > 0) {
+        uint32_t rbrace_tok = lastToken(tree, block_node);
+        uint32_t rbrace_start = tree->tokens.starts[rbrace_tok];
+        advanceSourceCursor(ag, rbrace_start);
+        rbrace_line = ag->source_line - gz->decl_line;
+        rbrace_column = ag->source_column;
+        src_locs_len = 7;
+    }
 
     // Build Func payload (Zir.Inst.Func: ret_ty, param_block, body_len).
     // (AstGen.zig:12182-12194)
@@ -11388,7 +11963,8 @@ static uint32_t addFunc(GenZir* gz, uint32_t src_node, uint32_t block_node,
 
     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);
+    ensureExtraCapacity(
+        ag, 3 + ret_ty_packed_len + fixup_body_len + src_locs_len);
     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
@@ -11408,16 +11984,18 @@ static uint32_t addFunc(GenZir* gz, uint32_t src_node, uint32_t block_node,
     appendBodyWithFixupsExtraRefs(
         ag, body, body_len, param_insts, param_insts_len);
 
-    // SrcLocs (AstGen.zig:12098-12106).
+    // SrcLocs + proto_hash only when body present (AstGen.zig:12081-12108).
-    uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
+    if (body_len > 0) {
-    ag->extra[ag->extra_len++] = lbrace_line;
+        uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
-    ag->extra[ag->extra_len++] = rbrace_line;
+        ag->extra[ag->extra_len++] = lbrace_line;
-    ag->extra[ag->extra_len++] = columns;
+        ag->extra[ag->extra_len++] = rbrace_line;
-    // proto_hash (4 words): zero for now.
+        ag->extra[ag->extra_len++] = columns;
-    ag->extra[ag->extra_len++] = 0;
+        // 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;
-    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
@@ -11443,11 +12021,19 @@ static uint32_t addFuncFancy(GenZir* gz, uint32_t src_node,
     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];
+    // SrcLocs only emitted when there's a body (AstGen.zig:12081-12108).
-    advanceSourceCursor(ag, rbrace_start);
+    uint32_t src_locs_len = 0;
-    uint32_t rbrace_line = ag->source_line - gz->decl_line;
+    uint32_t rbrace_line = 0;
-    uint32_t rbrace_column = ag->source_column;
+    uint32_t rbrace_column = 0;
+    if (body_len > 0) {
+        uint32_t rbrace_tok = lastToken(tree, block_node);
+        uint32_t rbrace_start = tree->tokens.starts[rbrace_tok];
+        advanceSourceCursor(ag, rbrace_start);
+        rbrace_line = ag->source_line - gz->decl_line;
+        rbrace_column = ag->source_column;
+        src_locs_len = 7;
+    }
 
     uint32_t fixup_body_len = countBodyLenAfterFixupsExtraRefs(
         ag, body, body_len, param_insts, param_insts_len);
@@ -11472,7 +12058,7 @@ static uint32_t addFuncFancy(GenZir* gz, uint32_t src_node,
 
     // 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;
+        + ((noalias_bits != 0) ? 1u : 0u) + fixup_body_len + src_locs_len;
     ensureExtraCapacity(ag, total_extra);
 
     // FuncFancy payload (Zir.zig:2589-2610).
@@ -11530,16 +12116,18 @@ static uint32_t addFuncFancy(GenZir* gz, uint32_t src_node,
     appendBodyWithFixupsExtraRefs(
         ag, body, body_len, param_insts, param_insts_len);
 
-    // SrcLocs (AstGen.zig:12098-12106).
+    // SrcLocs + proto_hash only when body present (AstGen.zig:12081-12108).
-    uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
+    if (body_len > 0) {
-    ag->extra[ag->extra_len++] = lbrace_line;
+        uint32_t columns = (lbrace_column & 0xFFFFu) | (rbrace_column << 16);
-    ag->extra[ag->extra_len++] = rbrace_line;
+        ag->extra[ag->extra_len++] = lbrace_line;
-    ag->extra[ag->extra_len++] = columns;
+        ag->extra[ag->extra_len++] = rbrace_line;
-    // proto_hash (4 words): zero for now.
+        ag->extra[ag->extra_len++] = columns;
-    ag->extra[ag->extra_len++] = 0;
+        // 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;
-    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;
@@ -11718,6 +12306,7 @@ static void fnDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
     // (Ast.zig:2003-2025, AstGen.zig:4102-4106, 4240-4247).
     bool is_pub = false;
     bool is_export = false;
+    bool is_extern = false;
     bool is_noinline = false;
     bool has_inline_keyword = false;
     for (uint32_t i = fn_token; i > 0;) {
@@ -11727,6 +12316,8 @@ static void fnDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
             is_pub = true;
         else if (ttag == TOKEN_KEYWORD_EXPORT)
             is_export = true;
+        else if (ttag == TOKEN_KEYWORD_EXTERN)
+            is_extern = true;
         else if (ttag == TOKEN_KEYWORD_NOINLINE)
             is_noinline = true;
         else if (ttag == TOKEN_KEYWORD_INLINE)
@@ -12121,21 +12712,54 @@ static void fnDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
     gzUnstack(&cc_gz);
 
     // --- Body handling ---
-    // For fn_proto* (no body): extern function, emit type only
+    // For fn_proto* (no body): extern function type
     // (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
+        // Upstream calls fnProtoExprInner with implicit_ccc=true.
-        // fnProtoExprInner is not yet ported.
+        // We use the already-computed params/ret but add implicit CCC
-        // TODO: implement fnProtoExprInner for extern fn support.
+        // if no explicit callconv was provided (AstGen.zig:1394-1396).
-        SET_ERROR(ag);
+        if (cc_ref == ZIR_REF_NONE && !has_inline_keyword) {
+            // Extern fn without explicit callconv: implicit C calling
+            // convention (AstGen.zig:1394-1396 via fnProtoExprInner).
+            cc_ref = addBuiltinValue(
+                &decl_gz, node, ZIR_BUILTIN_VALUE_CALLING_CONVENTION_C);
+        }
+        // Emit func instruction with no body (AstGen.zig:1402-1422).
+        bool need_fancy
+            = cc_ref != ZIR_REF_NONE || is_var_args || noalias_bits != 0;
+        if (need_fancy) {
+            func_ref = addFuncFancy(&decl_gz, node, 0, decl_inst, ret_ref,
+                ret_body, ret_body_len, cc_ref, cc_body, cc_body_len, NULL, 0,
+                param_insts, param_insts_len, 0, 0, is_var_args, false, false,
+                noalias_bits, ret_ty_is_generic, ret_param_refs,
+                ret_param_refs_len);
+        } else {
+            func_ref = addFunc(&decl_gz, node, 0, decl_inst, ret_ref, ret_body,
+                ret_body_len, NULL, 0, param_insts, param_insts_len, 0, 0,
+                false, ret_ty_is_generic, ret_param_refs, ret_param_refs_len);
+        }
+        // Patch ret_body/cc_body break_inlines (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;
+        }
+        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);
-        gzUnstack(&decl_gz);
+        // break_inline from decl_gz to decl_inst (AstGen.zig:4163).
-        ag->within_fn = prev_within_fn;
+        makeBreakInline(&decl_gz, decl_inst, func_ref,
-        return;
+            (int32_t)node - (int32_t)proto_node);
+        goto fn_decl_finish;
     }
 
     // --- Body (AstGen.zig:4415-4424) ---
@@ -12264,10 +12888,14 @@ static void fnDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
     makeBreakInline(
         &decl_gz, decl_inst, func_ref, (int32_t)node - (int32_t)proto_node);
 
+fn_decl_finish:
     // setDeclaration (AstGen.zig:4208-4225).
-    // Linkage: export > normal (AstGen.zig:4217).
+    // Linkage: extern > export > normal (AstGen.zig:4217).
+    ;
     DeclFlagsId decl_id;
-    if (is_export)
+    if (is_extern)
+        decl_id = is_pub ? DECL_ID_PUB_EXTERN_CONST : DECL_ID_EXTERN_CONST;
+    else 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;
@@ -13151,21 +13779,20 @@ static uint32_t containerDecl(
             else if (prev_tag == TOKEN_KEYWORD_EXTERN)
                 layout = 1;
         }
-        decl_inst = structDeclInner(ag, gz, node, members, members_len, layout,
+        decl_inst = structDeclInner(ag, gz, scope, node, members, members_len,
-            arg_node, name_strategy);
+            layout, arg_node, name_strategy);
         break;
     }
     case TOKEN_KEYWORD_ENUM:
-        decl_inst = enumDeclInner(
+        decl_inst = enumDeclInner(ag, gz, scope, node, members, members_len,
-            ag, gz, node, members, members_len, arg_node, name_strategy);
+            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);
+            ag, gz, scope, node, members, members_len, 0, 0, name_strategy);
         break;
     }
-    (void)scope;
 
     ag->fn_block = prev_fn_block;
     return decl_inst + ZIR_REF_START_INDEX;
@@ -13269,9 +13896,9 @@ static bool tokenIsUnderscore(const Ast* tree, uint32_t ident_token) {
 // 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,
+static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint32_t arg_node,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint8_t name_strategy) {
+    uint32_t arg_node, uint8_t name_strategy) {
     const Ast* tree = ag->tree;
 
     // --- First pass: count fields, values, decls, detect nonexhaustive ---
@@ -13307,8 +13934,7 @@ static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
 
     // Create namespace scope (AstGen.zig:5618-5623).
     ScopeNamespace namespace;
-    scopeNamespaceInit(
+    scopeNamespaceInit(&namespace, scope, node, decl_inst, gz, ag->within_fn);
-        &namespace, &gz->base, node, decl_inst, gz, ag->within_fn);
 
     advanceSourceCursorToNode(ag, node);
 
@@ -13449,9 +14075,10 @@ static uint32_t enumDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
 
 // --- tupleDecl (AstGen.zig:5192) ---
 
-static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, uint32_t node,
+static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint8_t layout,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint32_t backing_int_node) {
+    uint8_t layout, uint32_t backing_int_node) {
+    (void)scope;
     const Ast* tree = ag->tree;
 
     // layout must be auto for tuples (AstGen.zig:5204-5207).
@@ -13614,9 +14241,9 @@ static uint32_t tupleDecl(AstGenCtx* ag, GenZir* gz, uint32_t node,
 
 // --- structDeclInner (AstGen.zig:4926) ---
 
-static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
+static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, Scope* scope,
-    const uint32_t* members, uint32_t members_len, uint8_t layout,
+    uint32_t node, const uint32_t* members, uint32_t members_len,
-    uint32_t backing_int_node, uint8_t name_strategy) {
+    uint8_t layout, uint32_t backing_int_node, uint8_t name_strategy) {
     const Ast* tree = ag->tree;
 
     // Tuple detection (AstGen.zig:4939-4950).
@@ -13638,8 +14265,8 @@ static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
                 SET_ERROR(ag);
                 return reserveInstructionIndex(ag);
             }
-            return tupleDecl(
+            return tupleDecl(ag, gz, scope, node, members, members_len, layout,
-                ag, gz, node, members, members_len, layout, backing_int_node);
+                backing_int_node);
         }
     }
 
@@ -13660,8 +14287,7 @@ static uint32_t structDeclInner(AstGenCtx* ag, GenZir* gz, uint32_t node,
 
     // Create namespace scope (AstGen.zig:4973-4979).
     ScopeNamespace namespace;
-    scopeNamespaceInit(
+    scopeNamespaceInit(&namespace, scope, node, decl_inst, gz, ag->within_fn);
-        &namespace, &gz->base, node, decl_inst, gz, ag->within_fn);
 
     advanceSourceCursorToNode(ag, node);
 
@@ -15246,8 +15872,8 @@ Zir astGen(const Ast* ast) {
     const uint32_t* members = ast->extra_data.arr + members_start;
     uint32_t members_len = members_end - members_start;
 
-    structDeclInner(
+    structDeclInner(&ag, &gen_scope, &gen_scope.base, 0, members, members_len,
-        &ag, &gen_scope, 0, members, members_len, 0, 0, 0 /* parent */);
+        0, 0, 0 /* parent */);
 
     // Write imports list (AstGen.zig:227-244).
     writeImports(&ag);

stage0/astgen_test.zig

@@ -297,11 +297,7 @@ fn expectEqualZir(gpa: Allocator, ref: Zir, got: c.Zir) !void {
             const got_tag: u8 = @intCast(got.inst_tags[i]);
             if (ref_tag != got_tag) {
                 std.debug.print("first divergence at [{d}]: ref_tag={d} got_tag={d}\n", .{ i, ref_tag, got_tag });
-                // Show ref instruction data for this position.
+                // Data printing skipped to avoid tagged union safety panics.
-                const rd = ref_datas[i];
-                std.debug.print("  ref pl_node: src_node={d} payload={d}\n", .{
-                    rd.pl_node.src_node, rd.pl_node.payload_index,
-                });
                 // Scan for nearest declaration.
                 var j: usize = i;
                 while (j > 0) {