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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___CONCEPTS_ASSIGNABLE_H10#define _LIBCPP___CONCEPTS_ASSIGNABLE_H11 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_header21#endif22 23_LIBCPP_BEGIN_NAMESPACE_STD24 25#if _LIBCPP_STD_VER >= 2026 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 = std::forward<_Rhs>(__rhs) } -> same_as<_Lhs>;35 };36 37#endif // _LIBCPP_STD_VER >= 2038 39_LIBCPP_END_NAMESPACE_STD40 41#endif // _LIBCPP___CONCEPTS_ASSIGNABLE_H42