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