astgen: fix firstToken for container_decl, switch_case, asm, while/for, assign_destructure

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

astgen.c

@@ -601,6 +601,7 @@ static void advanceSourceCursor(AstGenCtx* ag, uint32_t end) {
 // 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];
@@ -654,7 +655,7 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
         case AST_NODE_PTR_TYPE_SENTINEL:
         case AST_NODE_PTR_TYPE:
         case AST_NODE_PTR_TYPE_BIT_RANGE:
-            return tree->nodes.main_tokens[n];
+            return tree->nodes.main_tokens[n] - end_offset;
 
         // Return main_token - 1: dot-prefixed inits and enum_literal
         // (Ast.zig:645-654).
@@ -667,7 +668,7 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
         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;
+            return tree->nodes.main_tokens[n] - 1 - end_offset;
 
         // Recurse into LHS: all binary ops and compound expressions
         // (Ast.zig:656-733).
@@ -767,7 +768,7 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
                     break;
                 }
             }
-            return i;
+            return i - end_offset;
         }
         // Fn decls: scan backwards for modifiers (Ast.zig:737-759).
         case AST_NODE_FN_DECL:
@@ -788,7 +789,7 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
                     break;
                 }
             }
-            return i;
+            return i - end_offset;
         }
         // Container fields: check for preceding comptime (Ast.zig:761-769).
         case AST_NODE_CONTAINER_FIELD_INIT:
@@ -796,8 +797,8 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
         case AST_NODE_CONTAINER_FIELD: {
             uint32_t mt = tree->nodes.main_tokens[n];
             if (mt > 0 && tree->tokens.tags[mt - 1] == TOKEN_KEYWORD_COMPTIME)
-                return mt - 1;
+                end_offset++;
-            return mt;
+            return mt - end_offset;
         }
         // Blocks: check for label (Ast.zig:794-805).
         case AST_NODE_BLOCK:
@@ -807,12 +808,99 @@ static uint32_t firstToken(const Ast* tree, uint32_t node) {
             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)
-                return lbrace - 2;
+                end_offset += 2;
-            return lbrace;
+            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];
+            return tree->nodes.main_tokens[n] - end_offset;
         }
     }
 }