diff --git a/App/lib/core/Gen/Func/FuncGenMixin.vp b/App/lib/core/Gen/Func/FuncGenMixin.vp
index f87b305..344125f 100644
--- a/App/lib/core/Gen/Func/FuncGenMixin.vp
+++ b/App/lib/core/Gen/Func/FuncGenMixin.vp
@@ -47,8 +47,35 @@ novirtual class FuncGenMixin(CallGenBase.CallGenBase):
         if promoted_name is not None: viperlib.snprintf(promoted_name, 64, "__closure_%s", func_name)
         mangled_promoted: str = self.Gen.FuncGenBase._mangle_name(trans, promoted_name)
 
-        # 2. Create the promoted function: define i32 @__closure_{name}(i8* %env, args...)
-        func: mlirlite.Function* = mlirlite.create_function(pool, mod, mangled_promoted, i32_ty)
+        # 2. Create the promoted function: define <ret> @__closure_{name}(i8* %env, args...)
+        # 返回类型**跟随 `-> T` 注解**。原实现写死 i32：于是 `def Inner(p: char*) -> char*: return p`
+        # 生成 `define i32 @__closure_Inner(i8* %env, i8* %p)`，而 `return p` 要把 char* 隐式转 i32
+        # → 撞 coerce_to_type 的 CastError（现场：EscapeMethodTest 的 (C) 用例）。那是"嵌套 def
+        # 只支持 int 返回"这个预先存在的缺口，此前被同文件更早的用例报错掩盖。
+        # 约定（最小改动的边界）：
+        #   · `fd.returns is None` 或注解是 `None` / `t.CVoid` → **保持 i32**（不改既有 ABI，
+        #     避免打断现有"无返回值/无注解"的嵌套 def；这是已知缺口，不在本次范围内）；
+        #   · 其余注解采用 resolve_annotation_type 的结果；解析不出 → fail-fast，不静默兜底。
+        ret_ty_n: mlirlite.LLVMType* = i32_ty
+        if fd.returns is not None:
+            keep_i32_n: int = 0
+            if fd.returns.kind() == ast.ASTKind.Constant:
+                rc_n: ast.Constant* = ast.Constant*(fd.returns)
+                if rc_n is not None and rc_n.const_kind == ast.CONST_NONE: keep_i32_n = 1
+            if self.Gen.TypeGenResolve._is_cvoid_marker(fd.returns, trans._imported_modules) != 0: keep_i32_n = 1
+            if keep_i32_n == 0:
+                rt_res_n: mlirlite.LLVMType* = self.Gen.TypeGenResolve.resolve_annotation_type(pool, fd.returns, trans._imported_modules, trans._from_imports, trans, 0)
+                if rt_res_n is None:
+                    self.Gen.TypeGenErr.fatal_error(fd, f"nested function '{fd.name}': cannot resolve the return type annotation for the promoted closure", "TypeError")
+                else:
+                    rt_is_void_n: int = 0
+                    match rt_res_n:
+                        case mlirlite.LLVMType.Void():
+                            rt_is_void_n = 1
+                        case _:
+                            pass
+                    if rt_is_void_n == 0: ret_ty_n = rt_res_n
+        func: mlirlite.Function* = mlirlite.create_function(pool, mod, mangled_promoted, ret_ty_n)
         if func is None: return 0
         mlirlite.add_param(pool, func, i8_ptr_ty, "%env")
 
@@ -225,8 +252,13 @@ novirtual class FuncGenMixin(CallGenBase.CallGenBase):
         if last_is_return == 0:
             # M3：隐式收尾也是函数出口，先释放本嵌套函数登记的 slife
             self.Gen.VarGen._SlifeEmitFrees(pool, func_builder, mod, trans)
-            zero_val: mlirlite.Value* = mlirlite.const_int32(pool, 0)
-            mlirlite.build_ret(func_builder, zero_val)
+            # 零值必须与**本函数的返回类型**一致（原实现写死 const_int32(0)：一旦返回类型改为
+            # `char*` 之类，`ret i32 0` 与签名不符，llc 会直接拒绝）。ret_ty_n 见第 2 步。
+            zero_val: mlirlite.Value* = mlirlite.ConstZero(pool, ret_ty_n)
+            if zero_val is None:
+                self.Gen.TypeGenErr.fatal_error(fd, f"nested function '{fd.name}': flow falls off the end without an implicit return and the return type has no zero value", "TypeError")
+            else:
+                mlirlite.build_ret(func_builder, zero_val)
 
         # M3：弹回外层登记区间（释放已在本嵌套函数各出口完成）
         self.Gen.VarGen._SlifeRestore(old_slife_base)