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 27 template <class _Ap, class _Bp> 28 using _CopyConst = _If<is_const_v<_Ap>, const _Bp, _Bp>; 29 30 template <class _Ap, class _Bp> 31 using _OverrideRef = _If<is_rvalue_reference_v<_Ap>, remove_reference_t<_Bp>&&, _Bp&>; 32 33 template <class _Ap, class _Bp> 34 using _ForwardLike = _OverrideRef<_Ap&&, _CopyConst<remove_reference_t<_Ap>, remove_reference_t<_Bp>>>; 35 36 template <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