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_CONCEPTS_H
11#define _LIBCPP___FORMAT_CONCEPTS_H
12
13#include <__concepts/same_as.h>
14#include <__concepts/semiregular.h>
15#include <__config>
16#include <__format/format_parse_context.h>
17#include <__fwd/format.h>
18#include <__fwd/tuple.h>
19#include <__tuple/tuple_size.h>
20#include <__type_traits/is_specialization.h>
21#include <__type_traits/remove_const.h>
22#include <__type_traits/remove_reference.h>
23#include <__utility/pair.h>
24
25#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
26# pragma GCC system_header
27#endif
28
29_LIBCPP_BEGIN_NAMESPACE_STD
30
31#if _LIBCPP_STD_VER >= 20
32
33/// The character type specializations of \ref formatter.
34template <class _CharT>
35concept __fmt_char_type =
36 same_as<_CharT, char>
37# if _LIBCPP_HAS_WIDE_CHARACTERS
38 || same_as<_CharT, wchar_t>
39# endif
40 ;
41
42// The output iterator isn't specified. A formatter should accept any
43// output_iterator. This iterator is a minimal iterator to test the concept.
44// (Note testing for (w)format_context would be a valid choice, but requires
45// selecting the proper one depending on the type of _CharT.)
46template <class _CharT>
47using __fmt_iter_for _LIBCPP_NODEBUG = _CharT*;
48
49template <class _Tp, class _Context, class _Formatter = typename _Context::template formatter_type<remove_const_t<_Tp>>>
50concept __formattable_with =
51 semiregular<_Formatter> &&
52 requires(_Formatter& __f,
53 const _Formatter& __cf,
54 _Tp&& __t,
55 _Context __fc,
56 basic_format_parse_context<typename _Context::char_type> __pc) {
57 { __f.parse(__pc) } -> same_as<typename decltype(__pc)::iterator>;
58 { __cf.format(__t, __fc) } -> same_as<typename _Context::iterator>;
59 };
60
61template <class _Tp, class _CharT>
62concept __formattable =
63 __formattable_with<remove_reference_t<_Tp>, basic_format_context<__fmt_iter_for<_CharT>, _CharT>>;
64
65# if _LIBCPP_STD_VER >= 23
66template <class _Tp, class _CharT>
67concept formattable = __formattable<_Tp, _CharT>;
68
69// [tuple.like] defines a tuple-like exposition only concept. This concept is
70// not related to that. Therefore it uses a different name for the concept.
71//
72// TODO FMT Add a test to validate we fail when using that concept after P2165
73// has been implemented.
74template <class _Tp>
75concept __fmt_pair_like =
76 __is_specialization_v<_Tp, pair> || (__is_specialization_v<_Tp, tuple> && tuple_size_v<_Tp> == 2);
77
78# endif // _LIBCPP_STD_VER >= 23
79#endif // _LIBCPP_STD_VER >= 20
80
81_LIBCPP_END_NAMESPACE_STD
82
83#endif // _LIBCPP___FORMAT_CONCEPTS_H
84