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___CONCEPTS_ASSIGNABLE_H 10#define _LIBCPP___CONCEPTS_ASSIGNABLE_H 11 12#include <__concepts/common_reference_with.h> 13#include <__concepts/same_as.h> 14#include <__config> 15#include <__type_traits/is_reference.h> 16#include <__type_traits/make_const_lvalue_ref.h> 17#include <__utility/forward.h> 18 19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20# pragma GCC system_header 21#endif 22 23_LIBCPP_BEGIN_NAMESPACE_STD 24 25#if _LIBCPP_STD_VER > 17 26 27// [concept.assignable] 28 29template<class _Lhs, class _Rhs> 30concept assignable_from = 31 is_lvalue_reference_v<_Lhs> && 32 common_reference_with<__make_const_lvalue_ref<_Lhs>, __make_const_lvalue_ref<_Rhs>> && 33 requires (_Lhs __lhs, _Rhs&& __rhs) { 34 { __lhs = _VSTD::forward<_Rhs>(__rhs) } -> same_as<_Lhs>; 35 }; 36 37#endif // _LIBCPP_STD_VER > 17 38 39_LIBCPP_END_NAMESPACE_STD 40 41#endif // _LIBCPP___CONCEPTS_ASSIGNABLE_H 42