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/void_t.h> 14 15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16 # pragma GCC system_header 17 #endif 18 19 #if _LIBCPP_STD_VER >= 20 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< _Tp, __void_t<typename _Tp::promise_type> > { 38 using promise_type = typename _Tp::promise_type; 39 }; 40 41 template <class _Ret, class... _Args> 42 struct coroutine_traits : public __coroutine_traits_sfinae<_Ret> {}; 43 44 _LIBCPP_END_NAMESPACE_STD 45 46 #endif // __LIBCPP_STD_VER >= 20 47 48 #endif // _LIBCPP___COROUTINE_COROUTINE_TRAITS_H 49