1//===----------------------------------------------------------------------===//
 2//
 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 4// See https://llvm.org/LICENSE.txt for license information.
 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 6//
 7//===----------------------------------------------------------------------===//
 8
 9#ifndef _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
10#define _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
11
12#include <__config>
13#include <__type_traits/make_const_lvalue_ref.h>
14#include <__utility/declval.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
24template <class, class, class>
25struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result {};
26
27template <class _Tp, class _Up>
28struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result<
29    _Tp,
30    _Up,
31    decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>(), void())> {
32  using type _LIBCPP_NODEBUG =
33      decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>());
34};
35
36template <class _Tp, class _Up = _Tp>
37struct _LIBCPP_NO_SPECIALIZATIONS compare_three_way_result : __compare_three_way_result<_Tp, _Up, void> {};
38
39template <class _Tp, class _Up = _Tp>
40using compare_three_way_result_t = typename compare_three_way_result<_Tp, _Up>::type;
41
42#endif // _LIBCPP_STD_VER >= 20
43
44_LIBCPP_END_NAMESPACE_STD
45
46#endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H