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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___COROUTINE_COROUTINE_TRAITS_H
#define _LIBCPP___COROUTINE_COROUTINE_TRAITS_H
#include <__config>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_COROUTINES)
_LIBCPP_BEGIN_NAMESPACE_STD
// [coroutine.traits]
// [coroutine.traits.primary]
// The header <coroutine> defined the primary template coroutine_traits such that
// if ArgTypes is a parameter pack of types and if the qualified-id R::promise_type
// is valid and denotes a type ([temp.deduct]), then coroutine_traits<R, ArgTypes...>
// has the following publicly accessible memebr:
//
// using promise_type = typename R::promise_type;
//
// Otherwise, coroutine_traits<R, ArgTypes...> has no members.
template <class _Tp, class = void>
struct __coroutine_traits_sfinae {};
template <class _Tp>
struct __coroutine_traits_sfinae<
_Tp, typename __void_t<typename _Tp::promise_type>::type>
{
using promise_type = typename _Tp::promise_type;
};
template <class _Ret, class... _Args>
struct coroutine_traits
: public __coroutine_traits_sfinae<_Ret>
{
};
_LIBCPP_END_NAMESPACE_STD
#endif // __LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_COROUTINES)
#endif // _LIBCPP___COROUTINE_COROUTINE_TRAITS_H
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