libcxx/include/__format/concepts.h

   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.
  34 template <class _CharT>
  35 concept __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.)
  46 template <class _CharT>
  47 using __fmt_iter_for = _CharT*;
  48
  49 template <class _Tp, class _Context, class _Formatter = typename _Context::template formatter_type<remove_const_t<_Tp>>>
  50 concept __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
  61 template <class _Tp, class _CharT>
  62 concept __formattable =
  63     __formattable_with<remove_reference_t<_Tp>, basic_format_context<__fmt_iter_for<_CharT>, _CharT>>;
  64
  65 #  if _LIBCPP_STD_VER >= 23
  66 template <class _Tp, class _CharT>
  67 concept 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.
  74 template <class _Tp>
  75 concept __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