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_UNREACHABLE_SENTINEL_H
11 #define _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
12 
13 #include <__config>
14 #include <__iterator/concepts.h>
15 
16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17 #  pragma GCC system_header
18 #endif
19 
20 _LIBCPP_BEGIN_NAMESPACE_STD
21 
22 #if _LIBCPP_STD_VER >= 20
23 
24 struct unreachable_sentinel_t {
25   template<weakly_incrementable _Iter>
26   _LIBCPP_HIDE_FROM_ABI
27   friend constexpr bool operator==(unreachable_sentinel_t, const _Iter&) noexcept {
28     return false;
29   }
30 };
31 
32 inline constexpr unreachable_sentinel_t unreachable_sentinel{};
33 
34 #endif // _LIBCPP_STD_VER >= 20
35 
36 _LIBCPP_END_NAMESPACE_STD
37 
38 #endif // _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
39