feat: trait 接口系统 — trait Show { fn method } + extend Trait Struct { }

src/sema/sema.c

@@ -558,6 +558,26 @@ static void analyze_method_call(AstNode* node, Scope* scope, ErrorList* errors,
     snprintf(mangled, sizeof(mangled), "%s$%s", recv_struct,
              node->as.method_call.method_name);
     Symbol* sym = scope_lookup(scope, mangled);
+    // trait 方法 fallback: 搜索所有作用域中以 $method_name 结尾的符号
+    if (!sym || sym->kind != SYM_FUNCTION) {
+        char suffix[256];
+        snprintf(suffix, sizeof(suffix), "$%s", node->as.method_call.method_name);
+        size_t suf_len = strlen(suffix);
+        for (const Scope* sc = scope; sc; sc = sc->parent) {
+            for (Symbol* s = sc->head; s; s = s->next) {
+                if (s->kind == SYM_FUNCTION) {
+                    size_t name_len = strlen(s->name);
+                    if (name_len > suf_len && strcmp(s->name + name_len - suf_len, suffix) == 0) {
+                        sym = s;
+                        // 更新 method_name 为找到的完整函数名（codegen 需要）
+                        node->as.method_call.method_name = s->name;
+                        break;
+                    }
+                }
+            }
+            if (sym) break;
+        }
+    }
     if (!sym || sym->kind != SYM_FUNCTION) {
         error_add(errors, "<sema>", node->loc.line, node->loc.col,
                   "结构体 '%s' 没有方法 '%s'", recv_struct,
@@ -657,6 +677,7 @@ static void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena*
             size_t extra_fn = 0;
             for (size_t i = 0; i < node->as.program.impl_count; i++) {
                 AstNode* impl = node->as.program.impls[i];
+                if (impl->kind == AST_TRAIT_DECL) continue;
                 extra_fn += impl->as.impl_block.method_count;
             }
             if (extra_fn > 0) {
@@ -668,6 +689,7 @@ static void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena*
 
                 for (size_t i = 0; i < node->as.program.impl_count; i++) {
                     AstNode* impl = node->as.program.impls[i];
+                    if (impl->kind == AST_TRAIT_DECL) continue;  // 跳过 trait 声明
                     const char* st_name = impl->as.impl_block.struct_name;
                     // 验证目标结构体存在
                     Symbol* st_sym = scope_lookup_struct(scope, st_name);
@@ -802,7 +824,8 @@ static void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena*
         const char* saved_name = current_return_struct_name;
         current_return_type = node->as.function.return_type;
         current_return_struct_name = node->as.function.return_struct_type_name;
-        analyze_node(node->as.function.body, fn_scope, errors, a);
+        if (node->as.function.body)
+            analyze_node(node->as.function.body, fn_scope, errors, a);
         current_return_type = saved;
         current_return_struct_name = saved_name;
         break;