1// -*- C++ -*- 2//===----------------------------------------------------------------------===// 3// 4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5// See https://llvm.org/LICENSE.txt for license information. 6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7// 8//===----------------------------------------------------------------------===// 9 10#ifndef _LIBCPP___UTILITY_FORWARD_LIKE_H 11#define _LIBCPP___UTILITY_FORWARD_LIKE_H 12 13#include <__config> 14#include <__type_traits/conditional.h> 15#include <__type_traits/is_const.h> 16#include <__type_traits/is_reference.h> 17#include <__type_traits/remove_reference.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 > 20 26 27template <class _Ap, class _Bp> 28using _CopyConst = _If<is_const_v<_Ap>, const _Bp, _Bp>; 29 30template <class _Ap, class _Bp> 31using _OverrideRef = _If<is_rvalue_reference_v<_Ap>, remove_reference_t<_Bp>&&, _Bp&>; 32 33template <class _Ap, class _Bp> 34using _ForwardLike = _OverrideRef<_Ap&&, _CopyConst<remove_reference_t<_Ap>, remove_reference_t<_Bp>>>; 35 36template <class _Tp, class _Up> 37[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto forward_like(_LIBCPP_LIFETIMEBOUND _Up&& __ux) noexcept 38 -> _ForwardLike<_Tp, _Up> { 39 return static_cast<_ForwardLike<_Tp, _Up>>(__ux); 40} 41 42#endif // _LIBCPP_STD_VER > 20 43 44_LIBCPP_END_NAMESPACE_STD 45 46#endif // _LIBCPP___UTILITY_FORWARD_LIKE_H 47