libcxx/include/__iterator/iter_move.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___ITERATOR_ITER_MOVE_H
  11 #define _LIBCPP___ITERATOR_ITER_MOVE_H
  12
  13 #include <__concepts/class_or_enum.h>
  14 #include <__config>
  15 #include <__iterator/iterator_traits.h>
  16 #include <__type_traits/is_reference.h>
  17 #include <__type_traits/remove_cvref.h>
  18 #include <__utility/declval.h>
  19 #include <__utility/forward.h>
  20 #include <__utility/move.h>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #  pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_PUSH_MACROS
  27 #include <__undef_macros>
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 #if _LIBCPP_STD_VER >= 20
  32
  33 // [iterator.cust.move]
  34
  35 namespace ranges {
  36 namespace __iter_move {
  37
  38 void iter_move() = delete;
  39
  40 template <class _Tp>
  41 concept __unqualified_iter_move = __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
  42   // NOLINTNEXTLINE(libcpp-robust-against-adl) iter_swap ADL calls should only be made through ranges::iter_swap
  43   iter_move(std::forward<_Tp>(__t));
  44 };
  45
  46 template <class _Tp>
  47 concept __move_deref = !__unqualified_iter_move<_Tp> && requires(_Tp&& __t) {
  48   *__t;
  49   requires is_lvalue_reference_v<decltype(*__t)>;
  50 };
  51
  52 template <class _Tp>
  53 concept __just_deref = !__unqualified_iter_move<_Tp> && !__move_deref<_Tp> && requires(_Tp&& __t) {
  54   *__t;
  55   requires(!is_lvalue_reference_v<decltype(*__t)>);
  56 };
  57
  58 // [iterator.cust.move]
  59
  60 struct __fn {
  61   // NOLINTBEGIN(libcpp-robust-against-adl) iter_move ADL calls should only be made through ranges::iter_move
  62   template <class _Ip>
  63     requires __unqualified_iter_move<_Ip>
  64   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator()(_Ip&& __i) const
  65       noexcept(noexcept(iter_move(std::forward<_Ip>(__i)))) {
  66     return iter_move(std::forward<_Ip>(__i));
  67   }
  68   // NOLINTEND(libcpp-robust-against-adl)
  69
  70   template <class _Ip>
  71     requires __move_deref<_Ip>
  72   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Ip&& __i) const
  73       noexcept(noexcept(std::move(*std::forward<_Ip>(__i)))) -> decltype(std::move(*std::forward<_Ip>(__i))) {
  74     return std::move(*std::forward<_Ip>(__i));
  75   }
  76
  77   template <class _Ip>
  78     requires __just_deref<_Ip>
  79   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Ip&& __i) const
  80       noexcept(noexcept(*std::forward<_Ip>(__i))) -> decltype(*std::forward<_Ip>(__i)) {
  81     return *std::forward<_Ip>(__i);
  82   }
  83 };
  84 } // namespace __iter_move
  85
  86 inline namespace __cpo {
  87 inline constexpr auto iter_move = __iter_move::__fn{};
  88 } // namespace __cpo
  89 } // namespace ranges
  90
  91 template <__dereferenceable _Tp>
  92   requires requires(_Tp& __t) {
  93     { ranges::iter_move(__t) } -> __can_reference;
  94   }
  95 using iter_rvalue_reference_t = decltype(ranges::iter_move(std::declval<_Tp&>()));
  96
  97 #endif // _LIBCPP_STD_VER >= 20
  98
  99 _LIBCPP_END_NAMESPACE_STD
 100
 101 _LIBCPP_POP_MACROS
 102
 103 #endif // _LIBCPP___ITERATOR_ITER_MOVE_H