libcxx/include/__utility/forward.h

   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_H
  11 #define _LIBCPP___UTILITY_FORWARD_H
  12
  13 #include <__config>
  14 #include <__type_traits/is_reference.h>
  15 #include <__type_traits/remove_reference.h>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 template <class _Tp>
  24 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp&&
  25 forward(_LIBCPP_LIFETIMEBOUND __libcpp_remove_reference_t<_Tp>& __t) _NOEXCEPT {
  26   return static_cast<_Tp&&>(__t);
  27 }
  28
  29 template <class _Tp>
  30 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp&&
  31 forward(_LIBCPP_LIFETIMEBOUND __libcpp_remove_reference_t<_Tp>&& __t) _NOEXCEPT {
  32   static_assert(!is_lvalue_reference<_Tp>::value, "cannot forward an rvalue as an lvalue");
  33   return static_cast<_Tp&&>(__t);
  34 }
  35
  36 _LIBCPP_END_NAMESPACE_STD
  37
  38 #endif // _LIBCPP___UTILITY_FORWARD_H