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___RANGES_DANGLING_H
11#define _LIBCPP___RANGES_DANGLING_H
12
13#include <__config>
14#include <__ranges/access.h>
15#include <__ranges/concepts.h>
16#include <__type_traits/conditional.h>
17
18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19# pragma GCC system_header
20#endif
21
22_LIBCPP_BEGIN_NAMESPACE_STD
23
24#if _LIBCPP_STD_VER >= 20
25
26namespace ranges {
27struct dangling {
28 dangling() = default;
29 _LIBCPP_HIDE_FROM_ABI constexpr dangling(auto&&...) noexcept {}
30};
31
32template <range _Rp>
33using borrowed_iterator_t = _If<borrowed_range<_Rp>, iterator_t<_Rp>, dangling>;
34
35// borrowed_subrange_t defined in <__ranges/subrange.h>
36} // namespace ranges
37
38#endif // _LIBCPP_STD_VER >= 20
39
40_LIBCPP_END_NAMESPACE_STD
41
42#endif // _LIBCPP___RANGES_DANGLING_H
43