1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___COROUTINE_COROUTINE_TRAITS_H 10 #define _LIBCPP___COROUTINE_COROUTINE_TRAITS_H 11 12 #include <__config> 13 #include <type_traits> 14 15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16 #pragma GCC system_header 17 #endif 18 19 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_COROUTINES) 20 21 _LIBCPP_BEGIN_NAMESPACE_STD 22 23 // [coroutine.traits] 24 // [coroutine.traits.primary] 25 // The header <coroutine> defined the primary template coroutine_traits such that 26 // if ArgTypes is a parameter pack of types and if the qualified-id R::promise_type 27 // is valid and denotes a type ([temp.deduct]), then coroutine_traits<R, ArgTypes...> 28 // has the following publicly accessible memebr: 29 // 30 // using promise_type = typename R::promise_type; 31 // 32 // Otherwise, coroutine_traits<R, ArgTypes...> has no members. 33 template <class _Tp, class = void> 34 struct __coroutine_traits_sfinae {}; 35 36 template <class _Tp> 37 struct __coroutine_traits_sfinae< 38 _Tp, typename __void_t<typename _Tp::promise_type>::type> 39 { 40 using promise_type = typename _Tp::promise_type; 41 }; 42 43 template <class _Ret, class... _Args> 44 struct coroutine_traits 45 : public __coroutine_traits_sfinae<_Ret> 46 { 47 }; 48 49 _LIBCPP_END_NAMESPACE_STD 50 51 #endif // __LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_COROUTINES) 52 53 #endif // _LIBCPP___COROUTINE_COROUTINE_TRAITS_H 54