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 
26 namespace ranges {
27 struct dangling {
28   dangling() = default;
29   _LIBCPP_HIDE_FROM_ABI constexpr dangling(auto&&...) noexcept {}
30 };
31 
32 template <range _Rp>
33 using 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