fix(tyck): func register, ret type recover

src/typecheck/program.mbt

@@ -82,6 +82,7 @@ pub fn Context::exit_scope(self : Context) -> Unit {
 }
 
 ///|
+#deprecated
 pub fn Context::set_current_func_ret_ty(self : Context, ty : TypeKind) -> Unit {
   self.current_func_ret_ty = Some(ty)
 }
@@ -115,7 +116,9 @@ pub fn Context::check_program(
   }
   // 收集顶层函数声明
   for name, func in program.top_functions {
-    self.func_types.set(name, self.check_top_function_type_decl(func))
+    let func_type = self.check_top_function_type_decl(func)
+    self.func_types.set(name, func_type)
+    self.type_env.set(name, { kind: func_type, mutable: false })
   }
   // 补充内建函数类型
   self.add_intrinsic_functions()

src/typecheck/stmt_local_function.mbt

@@ -26,8 +26,9 @@ pub fn Context::check_local_function(
   let func_type = Function(param_list.map(p => p.1.kind), ret_type)
   self.type_env.set(func.id, { kind: func_type, mutable: false })
   //
-  self.enter_scope()
+  let parent_func_ret_ty = self.current_func_ret_ty
   self.current_func_ret_ty = Some(ret_type)
+  self.enter_scope()
   //
   for param in param_list {
     let (param_name, param_type) = param
@@ -42,6 +43,7 @@ pub fn Context::check_local_function(
   }
   //
   self.exit_scope()
+  self.current_func_ret_ty = parent_func_ret_ty
   //
   {
     fname: func.id,

src/typecheck/top_function.mbt

@@ -31,10 +31,6 @@ pub fn Context::check_top_function_body(
   guard self.func_types.get(func.id) is Some(Function(param_types, ret_ty)) else {
     raise TypeCheckError("Function type for '\{func.id}' not found.")
   }
-  self.type_env.set(func.id, {
-    kind: Function(param_types, ret_ty),
-    mutable: false,
-  })
   self.enter_scope()
   self.current_func_ret_ty = Some(ret_ty)
   for i in 0..<param_names.length() {
@@ -48,6 +44,7 @@ pub fn Context::check_top_function_body(
     )
   }
   self.exit_scope()
+  self.current_func_ret_ty = None
   if func.user_defined_type is Some(UserDefined(udt)) {
     self.type_env.local_.remove("$Generic$\{udt}")
   }