[NFC][libc++][format] Uses uniform member signatures.

[Mordante]

Summary

The newer formatters for (tuple, vector<bool>::reference) specify the
formatter's parse and format member function. This signature is slightly
different from the signature for existing formatters. Adapt the existing
formatters to the new style.

[Mordante]

Fix CI.

libcxx/include/__chrono/formatter.h

_LIBCPP_HIDE_FROM_ABI constexpr bool __month_name_ok(const _Tp& __value) {
   else if constexpr (same_as<_Tp, chrono::year_month_weekday_last>)
     return __value.month().ok();
   else if constexpr (__is_hh_mm_ss<_Tp>)
     return true;
   else
     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
 }
 
-template <class _CharT, class _Tp>
+template <class _CharT, class _Tp, class _FormatContext>
 _LIBCPP_HIDE_FROM_ABI auto
 __format_chrono(const _Tp& __value,
-                auto& __ctx,
+                _FormatContext& __ctx,
                 __format_spec::__parsed_specifications<_CharT> __specs,
-                basic_string_view<_CharT> __chrono_specs) -> decltype(__ctx.out()) {
+                basic_string_view<_CharT> __chrono_specs) {
   basic_stringstream<_CharT> __sstr;
   // [time.format]/2
   // 2.1 - the "C" locale if the L option is not present in chrono-format-spec, otherwise
   // 2.2 - the locale passed to the formatting function if any, otherwise
   // 2.3 - the global locale.
   // Note that the __ctx's locale() call does 2.2 and 2.3.
   if (__specs.__chrono_.__locale_specific_form_)
     __sstr.imbue(__ctx.locale());
__format_chrono(const _Tp& __value,
   return __formatter::__write_string(basic_string_view<_CharT>{__str}, __ctx.out(), __specs);
 }
 
 } // namespace __formatter
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS __formatter_chrono {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto __parse(
-      basic_format_parse_context<_CharT>& __parse_ctx, __format_spec::__fields __fields, __format_spec::__flags __flags)
-      -> decltype(__parse_ctx.begin()) {
-    return __parser_.__parse(__parse_ctx, __fields, __flags);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
+  __parse(_ParseContext& __ctx, __format_spec::__fields __fields, __format_spec::__flags __flags) {
+    return __parser_.__parse(__ctx, __fields, __flags);
   }
 
-  template <class _Tp>
-  _LIBCPP_HIDE_FROM_ABI auto format(const _Tp& __value, auto& __ctx) const -> decltype(__ctx.out()) const {
+  template <class _Tp, class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(const _Tp& __value, _FormatContext& __ctx) const {
     return __formatter::__format_chrono(
         __value, __ctx, __parser_.__parser_.__get_parsed_chrono_specifications(__ctx), __parser_.__chrono_specs_);
   }
 
   __format_spec::__parser_chrono<_CharT> __parser_;
 };
 
 template <class _Duration, __fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::sys_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
   }
 };
 
 template <class _Duration, __fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::file_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
   }
 };
 
 template <class _Duration, __fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::local_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
     // The flags are not __clock since there is no associated time-zone.
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date_time);
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date_time);
   }
 };
 
 template <class _Rep, class _Period, __fmt_char_type _CharT>
 struct formatter<chrono::duration<_Rep, _Period>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
     // [time.format]/1
     // Giving a precision specification in the chrono-format-spec is valid only
     // for std::chrono::duration types where the representation type Rep is a
     // floating-point type. For all other Rep types, an exception of type
     // format_error is thrown if the chrono-format-spec contains a precision
     // specification.
     //
     // Note this doesn't refer to chrono::treat_as_floating_point_v<_Rep>.
     if constexpr (std::floating_point<_Rep>)
-      return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono_fractional, __format_spec::__flags::__duration);
+      return _Base::__parse(__ctx, __format_spec::__fields_chrono_fractional, __format_spec::__flags::__duration);
     else
-      return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__duration);
+      return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__duration);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::day, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__day);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__day);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday_indexed, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday_last, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_day, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_day);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_day);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_day_last, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_weekday, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_weekday_last, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year_month);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year_month);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_day, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_day_last, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_weekday, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
   }
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_weekday_last, _CharT>
     : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
   }
 };
 
 template <class _Duration, __fmt_char_type _CharT>
 struct formatter<chrono::hh_mm_ss<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__time);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__time);
   }
 };
 #endif // if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif //  _LIBCPP___CHRONO_FORMATTER_H

libcxx/include/__chrono/parser_std_format_spec.h

if ((__flags & __flags::__time_zone) != __flags::__time_zone)
     std::__throw_format_error("The supplied date time doesn't contain a time zone");
 }
 
 template <class _CharT>
 class _LIBCPP_TEMPLATE_VIS __parser_chrono {
   using _ConstIterator = typename basic_format_parse_context<_CharT>::const_iterator;
 
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  __parse(basic_format_parse_context<_CharT>& __parse_ctx, __fields __fields, __flags __flags)
-      -> decltype(__parse_ctx.begin()) {
-    _ConstIterator __begin = __parser_.__parse(__parse_ctx, __fields);
-    _ConstIterator __end   = __parse_ctx.end();
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
+  __parse(_ParseContext& __ctx, __fields __fields, __flags __flags) {
+    _ConstIterator __begin = __parser_.__parse(__ctx, __fields);
+    _ConstIterator __end   = __ctx.end();
     if (__begin == __end)
       return __begin;
 
     _ConstIterator __last = __parse_chrono_specs(__begin, __end, __flags);
     __chrono_specs_       = basic_string_view<_CharT>{__begin, __last};
 
     return __last;
   }

libcxx/include/__format/format_functions.h

 
 /// Helper class parse and handle argument.
 ///
 /// When parsing a handle which is not enabled the code is ill-formed.
 /// This helper uses the parser of the appropriate formatter for the stored type.
 template <class _CharT>
 class _LIBCPP_TEMPLATE_VIS __compile_time_handle {
 public:
-  _LIBCPP_HIDE_FROM_ABI
-  constexpr void __parse(basic_format_parse_context<_CharT>& __parse_ctx) const { __parse_(__parse_ctx); }
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr void __parse(_ParseContext& __ctx) const {
+    __parse_(__ctx);
+  }
 
   template <class _Tp>
   _LIBCPP_HIDE_FROM_ABI constexpr void __enable() {
-    __parse_ = [](basic_format_parse_context<_CharT>& __parse_ctx) {
+    __parse_ = [](basic_format_parse_context<_CharT>& __ctx) {
       formatter<_Tp, _CharT> __f;
-      __parse_ctx.advance_to(__f.parse(__parse_ctx));
+      __ctx.advance_to(__f.parse(__ctx));
     };
   }
 
   // Before calling __parse the proper handler needs to be set with __enable.
   // The default handler isn't a core constant expression.
   _LIBCPP_HIDE_FROM_ABI constexpr __compile_time_handle()
       : __parse_([](basic_format_parse_context<_CharT>&) { std::__throw_format_error("Not a handle"); }) {}
 

libcxx/include/__format/formatter_bool.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<bool, _CharT> {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_integral);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_integral);
     __format_spec::__process_parsed_bool(__parser_);
     return __result;
   }
 
-  _LIBCPP_HIDE_FROM_ABI auto format(bool __value, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(bool __value, _FormatContext& __ctx) const {
     switch (__parser_.__type_) {
     case __format_spec::__type::__default:
     case __format_spec::__type::__string:
       return __formatter::__format_bool(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx));
 
     case __format_spec::__type::__binary_lower_case:
     case __format_spec::__type::__binary_upper_case:
     case __format_spec::__type::__octal:

libcxx/include/__format/formatter_char.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS __formatter_char {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_integral);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_integral);
     __format_spec::__process_parsed_char(__parser_);
     return __result;
   }
 
-  _LIBCPP_HIDE_FROM_ABI auto format(_CharT __value, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_CharT __value, _FormatContext& __ctx) const {
     if (__parser_.__type_ == __format_spec::__type::__default || __parser_.__type_ == __format_spec::__type::__char)
       return __formatter::__format_char(__value, __ctx.out(), __parser_.__get_parsed_std_specifications(__ctx));
 
 #  if _LIBCPP_STD_VER >= 23
     if (__parser_.__type_ == __format_spec::__type::__debug)
       return __formatter::__format_escaped_char(__value, __ctx.out(), __parser_.__get_parsed_std_specifications(__ctx));
 #  endif
 
     if constexpr (sizeof(_CharT) <= sizeof(int))
       // Promotes _CharT to an integral type. This reduces the number of
       // instantiations of __format_integer reducing code size.
       return __formatter::__format_integer(
           static_cast<conditional_t<is_signed_v<_CharT>, int, unsigned>>(__value),
           __ctx,
           __parser_.__get_parsed_std_specifications(__ctx));
     else
       return __formatter::__format_integer(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx));
   }
 
-  _LIBCPP_HIDE_FROM_ABI auto format(char __value, auto& __ctx) const -> decltype(__ctx.out())
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(char __value, _FormatContext& __ctx) const
     requires(same_as<_CharT, wchar_t>)
   {
     return format(static_cast<wchar_t>(__value), __ctx);
   }
 
 #  if _LIBCPP_STD_VER >= 23
   _LIBCPP_HIDE_FROM_ABI constexpr void set_debug_format() { __parser_.__type_ = __format_spec::__type::__debug; }
 #  endif

libcxx/include/__format/formatter_floating_point.h

_LIBCPP_HIDE_FROM_ABI _OutIt __format_floating_point_non_finite(
   // leading zeros (following any indication of sign or base) to the field
   // width, except when applied to an infinity or NaN.
   if (__specs.__alignment_ == __format_spec::__alignment::__zero_padding)
     __specs.__alignment_ = __format_spec::__alignment::__right;
 
   return __formatter::__write(__buffer, __last, _VSTD::move(__out_it), __specs);
 }
 
-template <floating_point _Tp, class _CharT>
-_LIBCPP_HIDE_FROM_ABI auto
-__format_floating_point(_Tp __value, auto& __ctx, __format_spec::__parsed_specifications<_CharT> __specs)
-    -> decltype(__ctx.out()) {
+template <floating_point _Tp, class _CharT, class _FormatContext>
+_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+__format_floating_point(_Tp __value, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) {
   bool __negative = _VSTD::signbit(__value);
 
   if (!_VSTD::isfinite(__value)) [[unlikely]]
     return __formatter::__format_floating_point_non_finite(__ctx.out(), __specs, __negative, _VSTD::isnan(__value));
 
   // Depending on the std-format-spec string the sign and the value
   // might not be outputted together:
   // - zero-padding may insert additional '0' characters.
#  endif
   return __formatter::__write(__first, __result.__last, _VSTD::move(__out_it), __specs, __size);
 }
 
 } // namespace __formatter
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS __formatter_floating_point {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_floating_point);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_floating_point);
     __format_spec::__process_parsed_floating_point(__parser_);
     return __result;
   }
 
-  template <floating_point _Tp>
-  _LIBCPP_HIDE_FROM_ABI auto format(_Tp __value, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <floating_point _Tp, class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_Tp __value, _FormatContext& __ctx) const {
     return __formatter::__format_floating_point(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx));
   }
 
   __format_spec::__parser<_CharT> __parser_;
 };
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<float, _CharT>

libcxx/include/__format/formatter_integer.h

#endif
     _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
     template <__fmt_char_type _CharT>
     struct _LIBCPP_TEMPLATE_VIS __formatter_integer {
 
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_integral);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_integral);
     __format_spec::__process_parsed_integer(__parser_);
     return __result;
   }
 
-  template <integral _Tp>
-  _LIBCPP_HIDE_FROM_ABI auto format(_Tp __value, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <integral _Tp, class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_Tp __value, _FormatContext& __ctx) const {
     __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
 
     if (__specs.__std_.__type_ == __format_spec::__type::__char)
       return __formatter::__format_char(__value, __ctx.out(), __specs);
 
     using _Type = __make_32_64_or_128_bit_t<_Tp>;
     static_assert(!is_same<_Type, void>::value, "unsupported integral type used in __formatter_integer::__format");
 

libcxx/include/__format/formatter_integral.h

consteval size_t __buffer_size() noexcept
   requires(_Base == 16)
 {
   return numeric_limits<_Tp>::digits // The number of binary digits.
            / 4                       // Adjust to hexadecimal.
        + 2                           // Reserve space for the '0[Xx]' prefix.
        + 1;                          // Reserve space for the sign.
 }
 
-template <unsigned_integral _Tp, class _CharT>
-_LIBCPP_HIDE_FROM_ABI auto __format_integer(
+template <unsigned_integral _Tp, class _CharT, class _FormatContext>
+_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator __format_integer(
     _Tp __value,
-    auto& __ctx,
+    _FormatContext& __ctx,
     __format_spec::__parsed_specifications<_CharT> __specs,
     bool __negative,
     char* __begin,
     char* __end,
     const char* __prefix,
-    int __base) -> decltype(__ctx.out()) {
+    int __base) {
   char* __first = __formatter::__insert_sign(__begin, __negative, __specs.__std_.__sign_);
   if (__specs.__std_.__alternate_form_ && __prefix)
     while (*__prefix)
       *__first++ = *__prefix++;
 
   char* __last = __formatter::__to_buffer(__first, __end, __value, __base);
 
 #  ifndef _LIBCPP_HAS_NO_LOCALIZATION
#  endif
   }
 
   if (__specs.__std_.__type_ != __format_spec::__type::__hexadecimal_upper_case) [[likely]]
     return __formatter::__write(__first, __last, __ctx.out(), __specs);
 
   return __formatter::__write_transformed(__first, __last, __ctx.out(), __specs, __formatter::__hex_to_upper);
 }
 
-template <unsigned_integral _Tp, class _CharT>
-_LIBCPP_HIDE_FROM_ABI auto __format_integer(
-    _Tp __value, auto& __ctx, __format_spec::__parsed_specifications<_CharT> __specs, bool __negative = false)
-    -> decltype(__ctx.out()) {
+template <unsigned_integral _Tp, class _CharT, class _FormatContext>
+_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+__format_integer(_Tp __value,
+                 _FormatContext& __ctx,
+                 __format_spec::__parsed_specifications<_CharT> __specs,
+                 bool __negative = false) {
   switch (__specs.__std_.__type_) {
   case __format_spec::__type::__binary_lower_case: {
     array<char, __formatter::__buffer_size<decltype(__value), 2>()> __array;
     return __formatter::__format_integer(__value, __ctx, __specs, __negative, __array.begin(), __array.end(), "0b", 2);
   }
   case __format_spec::__type::__binary_upper_case: {
     array<char, __formatter::__buffer_size<decltype(__value), 2>()> __array;
     return __formatter::__format_integer(__value, __ctx, __specs, __negative, __array.begin(), __array.end(), "0B", 2);
case __format_spec::__type::__hexadecimal_upper_case: {
     return __formatter::__format_integer(__value, __ctx, __specs, __negative, __array.begin(), __array.end(), "0X", 16);
   }
   default:
     _LIBCPP_ASSERT(false, "The parse function should have validated the type");
     __libcpp_unreachable();
   }
 }
 
-template <signed_integral _Tp, class _CharT>
-_LIBCPP_HIDE_FROM_ABI auto
-__format_integer(_Tp __value, auto& __ctx, __format_spec::__parsed_specifications<_CharT> __specs)
-    -> decltype(__ctx.out()) {
+template <signed_integral _Tp, class _CharT, class _FormatContext>
+_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+__format_integer(_Tp __value, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) {
   // Depending on the std-format-spec string the sign and the value
   // might not be outputted together:
   // - alternate form may insert a prefix string.
   // - zero-padding may insert additional '0' characters.
   // Therefore the value is processed as a positive unsigned value.
   // The function @ref __insert_sign will a '-' when the value was negative.
   auto __r        = std::__to_unsigned_like(__value);
   bool __negative = __value < 0;

 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 template <>
 struct _LIBCPP_TEMPLATE_VIS __bool_strings<wchar_t> {
   static constexpr wstring_view __true{L"true"};
   static constexpr wstring_view __false{L"false"};
 };
 #  endif
 
-template <class _CharT>
-_LIBCPP_HIDE_FROM_ABI auto
-__format_bool(bool __value, auto& __ctx, __format_spec::__parsed_specifications<_CharT> __specs)
-    -> decltype(__ctx.out()) {
+template <class _CharT, class _FormatContext>
+_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+__format_bool(bool __value, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) {
 #  ifndef _LIBCPP_HAS_NO_LOCALIZATION
   if (__specs.__std_.__locale_specific_form_) {
     const auto& __np           = std::use_facet<numpunct<_CharT>>(__ctx.locale());
     basic_string<_CharT> __str = __value ? __np.truename() : __np.falsename();
     return __formatter::__write_string_no_precision(basic_string_view<_CharT>{__str}, __ctx.out(), __specs);
   }
 #  endif
   basic_string_view<_CharT> __str =

libcxx/include/__format/formatter_pointer.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS __formatter_pointer {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto
-  parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_pointer);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_pointer);
     __format_spec::__process_display_type_pointer(__parser_.__type_);
     return __result;
   }
 
-  _LIBCPP_HIDE_FROM_ABI auto format(const void* __ptr, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(const void* __ptr, _FormatContext& __ctx) const {
     __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
     __specs.__std_.__alternate_form_                       = true;
     __specs.__std_.__type_                                 = __format_spec::__type::__hexadecimal_lower_case;
     return __formatter::__format_integer(reinterpret_cast<uintptr_t>(__ptr), __ctx, __specs);
   }
 
   __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__right};
 };

libcxx/include/__format/formatter_string.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS __formatter_string {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-      -> decltype(__parse_ctx.begin()) {
-    auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_string);
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_string);
     __format_spec::__process_display_type_string(__parser_.__type_);
     return __result;
   }
 
-  _LIBCPP_HIDE_FROM_ABI auto format(basic_string_view<_CharT> __str, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+  format(basic_string_view<_CharT> __str, _FormatContext& __ctx) const {
 #  if _LIBCPP_STD_VER >= 23
     if (__parser_.__type_ == __format_spec::__type::__debug)
       return __formatter::__format_escaped_string(__str, __ctx.out(), __parser_.__get_parsed_std_specifications(__ctx));
 #  endif
 
     return __formatter::__write_string(__str, __ctx.out(), __parser_.__get_parsed_std_specifications(__ctx));
   }
 
 #  if _LIBCPP_STD_VER >= 23
   _LIBCPP_HIDE_FROM_ABI constexpr void set_debug_format() { __parser_.__type_ = __format_spec::__type::__debug; }
 #  endif
 
   __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
 };
 
 // Formatter const char*.
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<const _CharT*, _CharT>
     : public __formatter_string<_CharT> {
   using _Base = __formatter_string<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI auto format(const _CharT* __str, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(const _CharT* __str, _FormatContext& __ctx) const {
     _LIBCPP_ASSERT(__str, "The basic_format_arg constructor should have "
                           "prevented an invalid pointer.");
 
     __format_spec::__parsed_specifications<_CharT> __specs = _Base::__parser_.__get_parsed_std_specifications(__ctx);
 #  if _LIBCPP_STD_VER >= 23
     if (_Base::__parser_.__type_ == __format_spec::__type::__debug)
       return __formatter::__format_escaped_string(basic_string_view<_CharT>{__str}, __ctx.out(), __specs);
 #  endif

 };
 
 // Formatter char*.
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<_CharT*, _CharT>
     : public formatter<const _CharT*, _CharT> {
   using _Base = formatter<const _CharT*, _CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI auto format(_CharT* __str, auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_CharT* __str, _FormatContext& __ctx) const {
     return _Base::format(__str, __ctx);
   }
 };
 
 // Formatter char[].
 template <__fmt_char_type _CharT, size_t _Size>
 struct _LIBCPP_TEMPLATE_VIS formatter<_CharT[_Size], _CharT>
     : public __formatter_string<_CharT> {
   using _Base = __formatter_string<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI auto format(_CharT __str[_Size], auto& __ctx) const -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_CharT __str[_Size], _FormatContext& __ctx) const {
     return _Base::format(basic_string_view<_CharT>(__str, _Size), __ctx);
   }
 };
 
 // Formatter std::string.
 template <__fmt_char_type _CharT, class _Traits, class _Allocator>
 struct _LIBCPP_TEMPLATE_VIS formatter<basic_string<_CharT, _Traits, _Allocator>, _CharT>
     : public __formatter_string<_CharT> {
   using _Base = __formatter_string<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI auto format(const basic_string<_CharT, _Traits, _Allocator>& __str, auto& __ctx) const
-      -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+  format(const basic_string<_CharT, _Traits, _Allocator>& __str, _FormatContext& __ctx) const {
     // Drop _Traits and _Allocator to have one std::basic_string formatter.
     return _Base::format(basic_string_view<_CharT>(__str.data(), __str.size()), __ctx);
   }
 };
 
 // Formatter std::string_view.
 template <__fmt_char_type _CharT, class _Traits>
 struct _LIBCPP_TEMPLATE_VIS formatter<basic_string_view<_CharT, _Traits>, _CharT>
     : public __formatter_string<_CharT> {
   using _Base = __formatter_string<_CharT>;
 
-  _LIBCPP_HIDE_FROM_ABI auto format(basic_string_view<_CharT, _Traits> __str, auto& __ctx) const
-      -> decltype(__ctx.out()) {
+  template <class _FormatContext>
+  _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator
+  format(basic_string_view<_CharT, _Traits> __str, _FormatContext& __ctx) const {
     // Drop _Traits to have one std::basic_string_view formatter.
     return _Base::format(basic_string_view<_CharT>(__str.data(), __str.size()), __ctx);
   }
 };
 
 #endif //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___FORMAT_FORMATTER_STRING_H

libcxx/include/__format/formatter_tuple.h

struct _LIBCPP_TEMPLATE_VIS __formatter_tuple {
   }
   _LIBCPP_HIDE_FROM_ABI constexpr void
   set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
     __opening_bracket_ = __opening_bracket;
     __closing_bracket_ = __closing_bracket;
   }
 
   template <class _ParseContext>
-  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __parse_ctx) {
-    auto __begin = __parser_.__parse(__parse_ctx, __format_spec::__fields_tuple);
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_tuple);
 
-    auto __end = __parse_ctx.end();
+    auto __end = __ctx.end();
     if (__begin != __end) {
       if (*__begin == _CharT('m')) {
         if constexpr (sizeof...(_Args) == 2) {
           set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
           set_brackets({}, {});
           ++__begin;
         } else
           std::__throw_format_error("The format specifier m requires a pair or a two-element tuple");
       } else if (*__begin == _CharT('n')) {
         set_brackets({}, {});
         ++__begin;
       }
     }
 
     if (__begin != __end && *__begin != _CharT('}'))
       std::__throw_format_error("The format-spec should consume the input or end with a '}'");
 
-    __parse_ctx.advance_to(__begin);
+    __ctx.advance_to(__begin);
 
     // [format.tuple]/7
     //   ... For each element e in underlying_, if e.set_debug_format()
     //   is a valid expression, calls e.set_debug_format().
     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
       auto& __formatter = std::get<_Index>(__underlying_);
-      __formatter.parse(__parse_ctx);
+      __formatter.parse(__ctx);
       // Unlike the range_formatter we don't guard against evil parsers. Since
       // this format-spec never has a format-spec for the underlying type
       // adding the test would give additional overhead.
       std::__set_debug_format(__formatter);
     });
 
     return __begin;
   }

libcxx/include/__format/parser_std_format_spec.h

 #include <__undef_macros>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 namespace __format_spec {
 
-template <contiguous_iterator _Iterator>
+template <contiguous_iterator _Iterator, class _ParseContext>
 _LIBCPP_HIDE_FROM_ABI constexpr __format::__parse_number_result<_Iterator>
-__parse_arg_id(_Iterator __begin, _Iterator __end, auto& __parse_ctx) {
+__parse_arg_id(_Iterator __begin, _Iterator __end, _ParseContext& __ctx) {
   using _CharT = iter_value_t<_Iterator>;
   // This function is a wrapper to call the real parser. But it does the
   // validation for the pre-conditions and post-conditions.
   if (__begin == __end)
     std::__throw_format_error("End of input while parsing format-spec arg-id");
 
-  __format::__parse_number_result __r = __format::__parse_arg_id(__begin, __end, __parse_ctx);
+  __format::__parse_number_result __r = __format::__parse_arg_id(__begin, __end, __ctx);
 
   if (__r.__last == __end || *__r.__last != _CharT('}'))
     std::__throw_format_error("Invalid arg-id");
 
   ++__r.__last;
   return __r;
 }
 

 /// expected developers will create their own formatter specializations that
 /// inherit from the std::formatter specializations. This means this class
 /// must be ABI stable. To aid the stability the unused bits in the class are
 /// set to zero. That way they can be repurposed if a future revision of the
 /// Standards adds new fields to std-format-spec.
 template <class _CharT>
 class _LIBCPP_TEMPLATE_VIS __parser {
 public:
-  _LIBCPP_HIDE_FROM_ABI constexpr auto __parse(basic_format_parse_context<_CharT>& __parse_ctx, __fields __fields)
-      -> decltype(__parse_ctx.begin()) {
-
-    auto __begin = __parse_ctx.begin();
-    auto __end = __parse_ctx.end();
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator __parse(_ParseContext& __ctx, __fields __fields) {
+    auto __begin = __ctx.begin();
+    auto __end   = __ctx.end();
     if (__begin == __end)
       return __begin;
 
     if (__parse_fill_align(__begin, __end, __fields.__use_range_fill_) && __begin == __end)
       return __begin;
 
     if (__fields.__sign_ && __parse_sign(__begin) && __begin == __end)
       return __begin;
 
     if (__fields.__alternate_form_ && __parse_alternate_form(__begin) && __begin == __end)
       return __begin;
 
     if (__fields.__zero_padding_ && __parse_zero_padding(__begin) && __begin == __end)
       return __begin;
 
-    if (__parse_width(__begin, __end, __parse_ctx) && __begin == __end)
+    if (__parse_width(__begin, __end, __ctx) && __begin == __end)
       return __begin;
 
-    if (__fields.__precision_ && __parse_precision(__begin, __end, __parse_ctx) && __begin == __end)
+    if (__fields.__precision_ && __parse_precision(__begin, __end, __ctx) && __begin == __end)
       return __begin;
 
     if (__fields.__locale_specific_form_ && __parse_locale_specific_form(__begin) && __begin == __end)
       return __begin;
 
     if (__fields.__type_) {
       __parse_type(__begin);
 
_LIBCPP_HIDE_FROM_ABI constexpr bool __parse_zero_padding(_Iterator& __begin) {
 
     if (__alignment_ == __alignment::__default)
       __alignment_ = __alignment::__zero_padding;
     ++__begin;
     return true;
   }
 
   template <contiguous_iterator _Iterator>
-  _LIBCPP_HIDE_FROM_ABI constexpr bool __parse_width(_Iterator& __begin, _Iterator __end, auto& __parse_ctx) {
+  _LIBCPP_HIDE_FROM_ABI constexpr bool __parse_width(_Iterator& __begin, _Iterator __end, auto& __ctx) {
     if (*__begin == _CharT('0'))
       std::__throw_format_error("A format-spec width field shouldn't have a leading zero");
 
     if (*__begin == _CharT('{')) {
-      __format::__parse_number_result __r = __format_spec::__parse_arg_id(++__begin, __end, __parse_ctx);
+      __format::__parse_number_result __r = __format_spec::__parse_arg_id(++__begin, __end, __ctx);
       __width_as_arg_ = true;
       __width_ = __r.__value;
       __begin = __r.__last;
       return true;
     }
 
     if (*__begin < _CharT('0') || *__begin > _CharT('9'))
       return false;
 
     __format::__parse_number_result __r = __format::__parse_number(__begin, __end);
     __width_ = __r.__value;
     _LIBCPP_ASSERT(__width_ != 0, "A zero value isn't allowed and should be impossible, "
                                   "due to validations in this function");
     __begin = __r.__last;
     return true;
   }
 
   template <contiguous_iterator _Iterator>
-  _LIBCPP_HIDE_FROM_ABI constexpr bool __parse_precision(_Iterator& __begin, _Iterator __end, auto& __parse_ctx) {
+  _LIBCPP_HIDE_FROM_ABI constexpr bool __parse_precision(_Iterator& __begin, _Iterator __end, auto& __ctx) {
     if (*__begin != _CharT('.'))
       return false;
 
     ++__begin;
     if (__begin == __end)
       std::__throw_format_error("End of input while parsing format-spec precision");
 
     if (*__begin == _CharT('{')) {
-      __format::__parse_number_result __arg_id = __format_spec::__parse_arg_id(++__begin, __end, __parse_ctx);
+      __format::__parse_number_result __arg_id = __format_spec::__parse_arg_id(++__begin, __end, __ctx);
       __precision_as_arg_ = true;
       __precision_ = __arg_id.__value;
       __begin = __arg_id.__last;
       return true;
     }
 
     if (*__begin < _CharT('0') || *__begin > _CharT('9'))
       std::__throw_format_error("The format-spec precision field doesn't contain a value or arg-id");

libcxx/include/__format/range_formatter.h

set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
     __opening_bracket_ = __opening_bracket;
     __closing_bracket_ = __closing_bracket;
   }
 
   _LIBCPP_HIDE_FROM_ABI constexpr formatter<_Tp, _CharT>& underlying() noexcept { return __underlying_; }
   _LIBCPP_HIDE_FROM_ABI constexpr const formatter<_Tp, _CharT>& underlying() const noexcept { return __underlying_; }
 
   template <class _ParseContext>
-  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __parse_ctx) {
-    auto __begin = __parser_.__parse(__parse_ctx, __format_spec::__fields_range);
-    auto __end   = __parse_ctx.end();
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_range);
+    auto __end   = __ctx.end();
     // Note the cases where __begin == __end in this code only happens when the
     // replacement-field has no terminating }, or when the parse is manually
     // called with a format-spec. The former is an error and the latter means
     // using a formatter without the format functions or print.
     if (__begin == __end) [[unlikely]]
-      return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
+      return __parse_empty_range_underlying_spec(__ctx, __begin);
 
     // The n field overrides a possible m type, therefore delay applying the
     // effect of n until the type has been procesed.
     bool __clear_brackets = (*__begin == _CharT('n'));
     if (__clear_brackets) {
       ++__begin;
       if (__begin == __end) [[unlikely]] {
         // Since there is no more data, clear the brackets before returning.
         set_brackets({}, {});
-        return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
+        return __parse_empty_range_underlying_spec(__ctx, __begin);
       }
     }
 
     __parse_type(__begin, __end);
     if (__clear_brackets)
       set_brackets({}, {});
     if (__begin == __end) [[unlikely]]
-      return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
+      return __parse_empty_range_underlying_spec(__ctx, __begin);
 
     bool __has_range_underlying_spec = *__begin == _CharT(':');
     if (__has_range_underlying_spec) {
       // range-underlying-spec:
       //   :  format-spec
       ++__begin;
     } else if (__begin != __end && *__begin != _CharT('}'))
       // When there is no underlaying range the current parse should have
       // consumed the format-spec. If not, the not consumed input will be
       // processed by the underlying. For example {:-} for a range in invalid,
       // the sign field is not present. Without this check the underlying_ will
       // get -} as input which my be valid.
       std::__throw_format_error("The format-spec should consume the input or end with a '}'");
 
-    __parse_ctx.advance_to(__begin);
-    __begin = __underlying_.parse(__parse_ctx);
+    __ctx.advance_to(__begin);
+    __begin = __underlying_.parse(__ctx);
 
     // This test should not be required if __has_range_underlying_spec is false.
     // However this test makes sure the underlying formatter left the parser in
     // a valid state. (Note this is not a full protection against evil parsers.
     // For example
     //   } this is test for the next argument {}
     //   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
     // could consume more than it should.
case _CharT('?'):
         ++__begin;
       } else
         std::__throw_format_error("The range-format-spec type ?s requires formatting a character type");
     }
   }
 
   template <class _ParseContext>
   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
-  __parse_empty_range_underlying_spec(_ParseContext& __parse_ctx, typename _ParseContext::iterator __begin) {
-    __parse_ctx.advance_to(__begin);
-    [[maybe_unused]] typename _ParseContext::iterator __result = __underlying_.parse(__parse_ctx);
+  __parse_empty_range_underlying_spec(_ParseContext& __ctx, typename _ParseContext::iterator __begin) {
+    __ctx.advance_to(__begin);
+    [[maybe_unused]] typename _ParseContext::iterator __result = __underlying_.parse(__ctx);
     _LIBCPP_ASSERT(__result == __begin,
                    "the underlying's parse function should not advance the input beyond the end of the input");
     return __begin;
   }
 
   formatter<_Tp, _CharT> __underlying_;
   basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
   basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "[");
   basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "]");
 };
 
 #endif //_LIBCPP_STD_VER >= 23
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___FORMAT_RANGE_FORMATTER_H

libcxx/include/thread

 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, __thread_id __id)
 {return __os << __id.__id_;}
 
 #if _LIBCPP_STD_VER >= 23
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<__thread_id, _CharT> {
   public:
-    _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
-        -> decltype(__parse_ctx.begin()) {
-        return __parser_.__parse(__parse_ctx, __format_spec::__fields_fill_align_width);
+    template <class _ParseContext>
+    _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+        return __parser_.__parse(__ctx, __format_spec::__fields_fill_align_width);
     }
 
-    _LIBCPP_HIDE_FROM_ABI auto format(__thread_id __id, auto& __ctx) const -> decltype(__ctx.out()) {
+    template <class _FormatContext>
+    _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(__thread_id __id, _FormatContext& __ctx) const {
         // In __threading_support __libcpp_thread_id is either a
         // unsigned long long or a pthread_t.
         //
         // The type of pthread_t is left unspecified in POSIX so it can be any
         // type. The most logical types are an integral or pointer.
         // On Linux systems pthread_t is an unsigned long long.
         // On Apple systems pthread_t is a pointer type.
         //

libcxx/utils/data/ignore_format.txt

 libcxx/include/__format/format_arg.h
 libcxx/include/__format/format_args.h
 libcxx/include/__format/format_arg_store.h
 libcxx/include/__format/format_context.h
 libcxx/include/__format/format_error.h
 libcxx/include/__format/format_functions.h
 libcxx/include/__format/format_parse_context.h
 libcxx/include/__format/format_string.h
-libcxx/include/__format/formatter_bool.h
 libcxx/include/__format/formatter_char.h
 libcxx/include/__format/formatter_floating_point.h
 libcxx/include/__format/formatter.h
 libcxx/include/__format/formatter_integer.h
 libcxx/include/__format/formatter_integral.h
 libcxx/include/__format/formatter_output.h
 libcxx/include/__format/formatter_pointer.h
 libcxx/include/__format/formatter_string.h