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___FORMAT_FMT_PAIR_LIKE_H
11#define _LIBCPP___FORMAT_FMT_PAIR_LIKE_H
12
13#include <__config>
14#include <__fwd/pair.h>
15#include <__fwd/tuple.h>
16#include <__tuple/tuple_size.h>
17#include <__type_traits/is_specialization.h>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20# pragma GCC system_header
21#endif
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25#if _LIBCPP_STD_VER >= 23
26
27// [tuple.like] defines a tuple-like exposition only concept. This concept is not related to that. Therefore it uses a
28// different name for the concept.
29//
30// TODO FMT Add a test to validate we fail when using that concept after P2165 has been implemented.
31
32// [format.range.fmtkind]/2.2.1 and [tab:formatter.range.type]:
33// "U is either a specialization of pair or a specialization of tuple such that tuple_size_v<U> is 2."
34template <class _Tp>
35concept __fmt_pair_like =
36 __is_specialization_v<_Tp, pair> || (__is_specialization_v<_Tp, tuple> && tuple_size_v<_Tp> == 2);
37
38#endif // _LIBCPP_STD_VER >= 23
39
40_LIBCPP_END_NAMESPACE_STD
41
42#endif // _LIBCPP___FORMAT_FMT_PAIR_LIKE_H
43