使用 remove_cvref 替换 decay

librf/src/def.h

@@ -38,6 +38,21 @@ extern std::atomic<intptr_t> g_resumef_task_count;
 extern std::atomic<intptr_t> g_resumef_evtctx_count;
 #endif
 
+namespace std
+{
+#if !_HAS_CXX20
+	template<class T>
+	struct remove_cvref
+	{
+		typedef std::remove_cv_t<std::remove_reference_t<T>> type;
+	};
+#if _HAS_CXX17
+	template<class T>
+	using remove_cvref_t = typename std::remove_cvref<T>::type;
+#endif
+#endif
+}
+
 namespace resumef
 {
 #if _HAS_CXX17
@@ -47,6 +62,7 @@ namespace resumef
 	template<class... _Mutexes>
 	using scoped_lock = std::lock_guard<_Mutexes...>;
 #endif
+
 	template<typename _PromiseT = void>
 	using coroutine_handle = std::experimental::coroutine_handle<_PromiseT>;
 

librf/src/rf_task.h

@@ -149,9 +149,9 @@ namespace resumef
 	//这个'函数对象'被调用后，返回generator<_Ty>/future_t<_Ty>类型
 	//然后'函数对象'作为异步执行的上下文状态保存起来
 	template<class _Ctx>
-	struct ctx_task_t : public task_t<typename std::decay<decltype(std::declval<_Ctx>()())>::type>
+	struct ctx_task_t : public task_t<typename std::remove_cvref<decltype(std::declval<_Ctx>()())>::type>
 	{
-		typedef task_t<typename std::decay<decltype(std::declval<_Ctx>()())>::type> base_type;
+		typedef task_t<typename std::remove_cvref<decltype(std::declval<_Ctx>()())>::type> base_type;
 		using base_type::_future;
 
 		typedef _Ctx context_type;

tutorial/test_async_modern_cb.cpp

@@ -82,7 +82,7 @@ __declspec(noinline)
 auto tostring_async(_Input_t&& value, _Callable_t&& token)
 {
 	//适配器类型
-	using _Adapter_t = modern_callback_adapter_t<std::decay_t<_Callable_t>, void(std::string)>;
+	using _Adapter_t = modern_callback_adapter_t<typename std::remove_cvref<_Callable_t>::type, void(std::string)>;
 	//通过适配器获得兼容_Signature_t类型的真正的回调，以及返回值_Return_t
 	auto adapter = typename _Adapter_t::traits(std::forward<_Callable_t>(token));
 
@@ -100,7 +100,7 @@ auto tostring_async(_Input_t&& value, _Callable_t&& token)
 
 //或者宏版本写法
 #define MODERN_CALLBACK_TRAITS(_Token_value, _Signature_t) \
-	using _Adapter_t = modern_callback_adapter_t<std::decay_t<_Callable_t>, _Signature_t>; \
+	using _Adapter_t = modern_callback_adapter_t<typename std::remove_cvref<_Callable_t>::type, _Signature_t>; \
 	auto _Adapter_value = typename _Adapter_t::traits(std::forward<_Callable_t>(_Token_value))
 #define MODERN_CALLBACK_CALL() std::move(std::get<0>(_Adapter_value))
 #define MODERN_CALLBACK_RETURN() return std::move(std::get<1>(_Adapter_value)).get()