diff --git a/src/codegen/codegen.c b/src/codegen/codegen.c
index 187a61d..2343fee 100644
--- a/src/codegen/codegen.c
+++ b/src/codegen/codegen.c
@@ -353,6 +353,7 @@ static LLVMValueRef codegen_expr(CgCtx* ctx, AstNode* node) {
         LLVMValueRef fn = find_fn(ctx, node->as.call.name);
         if (!fn) return NULL;
         LLVMValueRef args[16];
+        if (node->as.call.arg_count > 16) { ctx->error = "函数参数过多(最多16)"; return NULL; }
         for (size_t i = 0; i < node->as.call.arg_count; i++) {
             args[i] = codegen_expr(ctx, node->as.call.args[i]);
             if (!args[i]) return NULL;
@@ -440,6 +441,7 @@ static LLVMValueRef codegen_expr(CgCtx* ctx, AstNode* node) {
         LLVMValueRef fn = find_fn(ctx, mangled);
         if (!fn) return NULL;
         // 参数列表: [receiver, 用户参数...]
+        if (node->as.method_call.arg_count + 1 > 16) { ctx->error = "方法参数过多(最多15)"; return NULL; }
         LLVMValueRef args[16];
         args[0] = codegen_expr(ctx, node->as.method_call.receiver);
         if (!args[0]) return NULL;
diff --git a/src/driver/error.c b/src/driver/error.c
index bce4b4e..f4dbca5 100644
--- a/src/driver/error.c
+++ b/src/driver/error.c
@@ -1,22 +1,25 @@
 #include "error.h"
+#include "arena.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
 
-void error_init(ErrorList* list) {
-    list->capacity = 8;
-    list->errors = malloc(list->capacity * sizeof(ErrorInfo));
+void error_init(ErrorList* list, Arena* a) {
+    list->capacity = 64;
+    list->errors = arena_alloc(a, list->capacity * sizeof(ErrorInfo));
     list->count = 0;
+    list->arena = a;
     if (!list->errors) list->capacity = 0;
 }
 
 void error_add(ErrorList* list, const char* filename, int line, int col, const char* fmt, ...) {
     if (!list->errors) return;
     if (list->count >= list->capacity) {
-        size_t new_cap = list->capacity * 2;
-        ErrorInfo* new_errs = realloc(list->errors, new_cap * sizeof(ErrorInfo));
+        size_t new_cap = list->capacity + 64;
+        ErrorInfo* new_errs = arena_alloc(list->arena, new_cap * sizeof(ErrorInfo));
         if (!new_errs) return;
+        memcpy(new_errs, list->errors, list->capacity * sizeof(ErrorInfo));
         list->errors = new_errs;
         list->capacity = new_cap;
     }
@@ -26,12 +29,9 @@ void error_add(ErrorList* list, const char* filename, int line, int col, const c
     int n = vsnprintf(buf, sizeof(buf), fmt, args);
     va_end(args);
     if (n < 0) return;
-    char* msg = strdup(buf);
-    char* fname = strdup(filename);
-    if (!msg || !fname) {
-        free(msg); free(fname);
-        return;
-    }
+    char* msg = arena_strdup(list->arena, buf);
+    char* fname = arena_strdup(list->arena, filename);
+    if (!msg || !fname) return;
     list->errors[list->count++] = (ErrorInfo){
         .message = msg,
         .filename = fname,
diff --git a/src/driver/error.h b/src/driver/error.h
index 3305fd6..67f59fc 100644
--- a/src/driver/error.h
+++ b/src/driver/error.h
@@ -3,6 +3,8 @@
 
 #include <stddef.h>
 
+typedef struct Arena Arena;
+
 typedef struct {
     const char* message;
     const char* filename;
@@ -14,9 +16,10 @@ typedef struct {
     ErrorInfo* errors;
     size_t     count;
     size_t     capacity;
+    Arena*     arena;
 } ErrorList;
 
-void error_init(ErrorList* list);
+void error_init(ErrorList* list, Arena* a);
 void error_add(ErrorList* list, const char* filename, int line, int col, const char* fmt, ...);
 void error_print(const ErrorList* list);
 
diff --git a/src/driver/main.c b/src/driver/main.c
index c9ac57d..8ce38a8 100644
--- a/src/driver/main.c
+++ b/src/driver/main.c
@@ -86,7 +86,7 @@ int main(int argc, char** argv) {
     if (!arena.memory) { fprintf(stderr, "内存分配失败\n"); free(source); return 1; }
 
     ErrorInfo error = {0};
-    ErrorList error_list; error_init(&error_list);
+    ErrorList error_list; error_init(&error_list, &arena);
 
     // 3. 词法分析
     size_t token_count;
diff --git a/src/parser/parser.c b/src/parser/parser.c
index 73004f6..9fb5313 100644
--- a/src/parser/parser.c
+++ b/src/parser/parser.c
@@ -1031,8 +1031,6 @@ AstNode* parse(Arena* a, const Token* tokens, size_t count,
     AstNode* aliases[64];   int alias_count = 0;
     AstNode* enums[64];     int enum_count = 0;
     AstNode* impls[64];     int impl_count = 0;
-    AstNode* mods[64];      int mod_count = 0;
-    AstNode* uses[64];      int use_count = 0;
     while (peek(&p)->kind != TOK_EOF && !error->message) {
         // pub 前缀
         bool is_pub = false;
@@ -1179,20 +1177,12 @@ AstNode* parse(Arena* a, const Token* tokens, size_t count,
                 if (enum_count >= 64) break;
                 enums[enum_count++] = sub->as.program.enums[i];
             }
-            if (mod_count < 64) mods[mod_count++] = ast_make_mod_decl(a, mod_name, sub, tok_loc(mn));
+            /* mod 内容已内联合并到当前文件 */ ;
         } else if (peek(&p)->kind == TOK_USE) {
+            /* TODO: use 语句待实现符号导入 */ ;
             advance(&p);
-            const Token* path_tok = expect(&p, TOK_IDENT, error, "use 后应为模块名");
-            if (!path_tok) return NULL;
-            if (!expect(&p, TOK_COLON_COLON, error, "缺少 '::'")) return NULL;
-            const Token* item_tok = expect(&p, TOK_IDENT, error, "use 后应为项目名");
-            if (!item_tok) return NULL;
-            if (!expect(&p, TOK_SEMICOLON, error, "缺少 ';'")) return NULL;
-            if (use_count >= 64) { error->message = "use 过多 (最多64)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
-            uses[use_count++] = ast_make_use_decl(a,
-                arena_strdup_impl(p.arena, path_tok->start, path_tok->length),
-                arena_strdup_impl(p.arena, item_tok->start, item_tok->length),
-                tok_loc(path_tok));
+            while (peek(&p)->kind != TOK_SEMICOLON && peek(&p)->kind != TOK_EOF) advance(&p);
+            if (peek(&p)->kind == TOK_SEMICOLON) advance(&p);
         } else if (peek(&p)->kind == TOK_FN) {
             if (fn_count >= 256) { error->message = "函数过多 (最多256)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
             functions[fn_count++] = parse_function(&p, is_pub, error);
diff --git a/src/sema/sema.c b/src/sema/sema.c
index 75d9652..ee80610 100644
--- a/src/sema/sema.c
+++ b/src/sema/sema.c
@@ -558,19 +558,20 @@ 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
+    // trait 方法 fallback: 搜索所有作用域中以 $method_name 结尾且以 StructName 开头的符号
     if (!sym || sym->kind != SYM_FUNCTION) {
         char suffix[256];
         snprintf(suffix, sizeof(suffix), "$%s", node->as.method_call.method_name);
         size_t suf_len = strlen(suffix);
+        size_t recv_len = strlen(recv_struct);
         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) {
+                    if (name_len > suf_len + recv_len
+                        && strncmp(s->name, recv_struct, recv_len) == 0
+                        && 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;
                     }
                 }
@@ -578,6 +579,10 @@ static void analyze_method_call(AstNode* node, Scope* scope, ErrorList* errors,
             if (sym) break;
         }
     }
+    // 更新 method_name 为符号的实际名称（codegen 需要通过它找到 LLVM 函数）
+    if (sym && sym->kind == SYM_FUNCTION) {
+        node->as.method_call.method_name = sym->name;
+    }
     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,
@@ -700,6 +705,21 @@ static void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena*
                     }
                     for (size_t j = 0; j < impl->as.impl_block.method_count; j++) {
                         AstNode* method = impl->as.impl_block.methods[j];
+                        // Self → 实际结构体名（参数类型）
+                        for (size_t k = 0; k < method->as.function.param_count; k++) {
+                            AstNode* p = method->as.function.params[k];
+                            if (p->as.parameter.type == TYPE_STRUCT
+                                && p->as.parameter.struct_type_name
+                                && strcmp(p->as.parameter.struct_type_name, "Self") == 0) {
+                                p->as.parameter.struct_type_name = st_name;
+                            }
+                        }
+                        // Self → 实际结构体名（返回类型）
+                        if (method->as.function.return_type == TYPE_STRUCT
+                            && method->as.function.return_struct_type_name
+                            && strcmp(method->as.function.return_struct_type_name, "Self") == 0) {
+                            method->as.function.return_struct_type_name = st_name;
+                        }
                         // 构造改名后的函数名
                         char mangled[256];
                         snprintf(mangled, sizeof(mangled), "%s$%s", st_name,
diff --git a/test/programs/36_self_type.l b/test/programs/36_self_type.l
new file mode 100644
index 0000000..e2576b2
--- /dev/null
+++ b/test/programs/36_self_type.l
@@ -0,0 +1,28 @@
+trait Eq {
+    fn eq(self: Self, other: Self) -> bool;
+}
+
+struct Point { x: i64, y: i64 }
+
+extend Eq Point {
+    fn eq(self: Point, other: Point) -> bool {
+        return self.x == other.x && self.y == other.y;
+    }
+}
+
+fn main() -> i64 {
+    let p1 = Point { x: 10, y: 20 };
+    let p2 = Point { x: 10, y: 20 };
+    let p3 = Point { x: 99, y: 1 };
+    if p1.eq(p2) {
+        print_str("same");
+    } else {
+        print_str("diff");
+    }
+    if p1.eq(p3) {
+        print_str("same");
+    } else {
+        print_str("diff");
+    }
+    return 0;
+}
diff --git a/test/test_codegen.c b/test/test_codegen.c
index 77fb990..74e356c 100644
--- a/test/test_codegen.c
+++ b/test/test_codegen.c
@@ -491,7 +491,7 @@ void test_codegen_match() {
     AstNode* fns[] = { main_fn };
     AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, NULL, 0, enums, 1, NULL, 0, loc_at(1, 1));
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(prog, &errors, &a);
     ASSERT(errors.count == 0);
 
diff --git a/test/test_sema.c b/test/test_sema.c
index ed7a986..d2f9ae4 100644
--- a/test/test_sema.c
+++ b/test/test_sema.c
@@ -14,7 +14,7 @@ void test_type_error() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);
     arena_destroy(&a);
@@ -29,7 +29,7 @@ void test_undefined_var() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);
     arena_destroy(&a);
@@ -45,7 +45,7 @@ void test_simple_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -61,7 +61,7 @@ void test_let_mut_assign_ok() {
     ErrorInfo parse_err = {0};
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -77,7 +77,7 @@ void test_assign_immutable_error() {
     ErrorInfo parse_err = {0};
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // 不可变变量赋值应报错
     arena_destroy(&a);
@@ -93,7 +93,7 @@ void test_str_type_ok() {
     ErrorInfo parse_err = {0};
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -109,7 +109,7 @@ void test_str_concat_type_ok() {
     ErrorInfo parse_err = {0};
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -128,7 +128,7 @@ void test_struct_field_type_mismatch() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // y 字段类型不匹配: true 是 bool, 不是 i64
     arena_destroy(&a);
@@ -145,7 +145,7 @@ void test_struct_undefined() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // Unknown 未定义
     arena_destroy(&a);
@@ -162,7 +162,7 @@ void test_struct_field_count_mismatch() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // 缺少字段 'y'
     arena_destroy(&a);
@@ -182,7 +182,7 @@ void test_type_alias_ok() {
     ASSERT(ast != NULL);
     ASSERT(ast->as.program.alias_count == 1);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -200,7 +200,7 @@ void test_type_alias_struct() {
     ASSERT(ast != NULL);
     ASSERT(ast->as.program.alias_count == 1);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -217,7 +217,7 @@ void test_struct_nested_type_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);  // 嵌套结构体类型检查应通过
     arena_destroy(&a);
@@ -236,7 +236,7 @@ void test_enum_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -253,7 +253,7 @@ void test_enum_bad_variant() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // Yellow 不存在
     arena_destroy(&a);
@@ -272,7 +272,7 @@ void test_array_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -289,7 +289,7 @@ void test_array_index_type_error() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // true 不是 i64
     arena_destroy(&a);
@@ -306,7 +306,7 @@ void test_array_not_indexable() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // i64 不是数组
     arena_destroy(&a);
@@ -323,7 +323,7 @@ void test_array_assign_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -342,7 +342,7 @@ void test_method_call_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -359,7 +359,7 @@ void test_method_undefined() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count > 0);  // nope 不是 Point 的方法
     arena_destroy(&a);
@@ -378,7 +378,7 @@ void test_match_enum_sema_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);  // match 去糖后应通过类型检查
     arena_destroy(&a);
@@ -395,7 +395,7 @@ void test_match_int_sema_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);
     arena_destroy(&a);
@@ -412,7 +412,7 @@ void test_match_wildcard_only_sema_ok() {
     AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
     ASSERT(ast != NULL);
 
-    ErrorList errors; error_init(&errors);
+    ErrorList errors; error_init(&errors, &a);
     sema_analyze(ast, &errors, &a);
     ASSERT(errors.count == 0);  // 纯通配符 match 应通过
     arena_destroy(&a);