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 <__utility/forward.h>
17 #include <__utility/move.h>
18 #include <type_traits>
19 
20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 #if _LIBCPP_STD_VER > 17
27 
28 // [iterator.cust.move]
29 
30 namespace ranges {
31 namespace __iter_move {
32 
33 void iter_move();
34 
35 template <class _Tp>
36 concept __unqualified_iter_move =
37   __class_or_enum<remove_cvref_t<_Tp>> &&
38   requires (_Tp&& __t) {
39     iter_move(std::forward<_Tp>(__t));
40   };
41 
42 template<class _Tp>
43 concept __move_deref =
44   !__unqualified_iter_move<_Tp> &&
45   requires (_Tp&& __t) {
46     *__t;
47     requires is_lvalue_reference_v<decltype(*__t)>;
48   };
49 
50 template<class _Tp>
51 concept __just_deref =
52   !__unqualified_iter_move<_Tp> &&
53   !__move_deref<_Tp> &&
54   requires (_Tp&& __t) {
55     *__t;
56     requires (!is_lvalue_reference_v<decltype(*__t)>);
57   };
58 
59 // [iterator.cust.move]
60 
61 struct __fn {
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   {
67     return iter_move(std::forward<_Ip>(__i));
68   }
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))))
74     -> decltype(      std::move(*std::forward<_Ip>(__i)))
75     { return          std::move(*std::forward<_Ip>(__i)); }
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)))
81     -> decltype(      *std::forward<_Ip>(__i))
82     { return          *std::forward<_Ip>(__i); }
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) { { ranges::iter_move(__t) } -> __can_reference; }
93 using iter_rvalue_reference_t = decltype(ranges::iter_move(declval<_Tp&>()));
94 
95 #endif // _LIBCPP_STD_VER > 17
96 
97 _LIBCPP_END_NAMESPACE_STD
98 
99 #endif // _LIBCPP___ITERATOR_ITER_MOVE_H
100