[libc++][format] Adds range-default-formatter.
This adds an incomplete version where the specializations for the
format_kinds are disabled dummy formatters.
Implements part of
- P2585R0 Improving default container formatting
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D137271
NOKEYCHECK=True
GitOrigin-RevId: d184958bad5c23e11ee91a16d9c551e1922387bf
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index 1ae14411..7dc3ffa 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -310,6 +310,7 @@
__format/formatter_pointer.h
__format/formatter_string.h
__format/parser_std_format_spec.h
+ __format/range_default_formatter.h
__format/unicode.h
__functional/binary_function.h
__functional/binary_negate.h
@@ -626,6 +627,7 @@
__type_traits/is_scoped_enum.h
__type_traits/is_signed.h
__type_traits/is_signed_integer.h
+ __type_traits/is_specialization.h
__type_traits/is_standard_layout.h
__type_traits/is_swappable.h
__type_traits/is_trivial.h
diff --git a/include/__format/concepts.h b/include/__format/concepts.h
index 5407fee..fe4a7b9 100644
--- a/include/__format/concepts.h
+++ b/include/__format/concepts.h
@@ -15,6 +15,9 @@
#include <__config>
#include <__format/format_fwd.h>
#include <__format/format_parse_context.h>
+#include <__type_traits/is_specialization.h>
+#include <__utility/pair.h>
+#include <tuple>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -56,6 +59,17 @@
# if _LIBCPP_STD_VER > 20
template <class _Tp, class _CharT>
concept formattable = __formattable<_Tp, _CharT>;
+
+// [tuple.like] defines a tuple-like exposition only concept. This concept is
+// not related to that. Therefore it uses a different name for the concept.
+//
+// TODO FMT Add a test to validate we fail when using that concept after P2165
+// has been implemented.
+template <class _Tp>
+concept __fmt_pair_like = __is_specialization_v<_Tp, pair> ||
+ // Use a requires since tuple_size_v may fail to instantiate,
+ (__is_specialization_v<_Tp, tuple> && requires { tuple_size_v<_Tp> == 2; });
+
# endif //_LIBCPP_STD_VER > 20
#endif //_LIBCPP_STD_VER > 17
diff --git a/include/__format/range_default_formatter.h b/include/__format/range_default_formatter.h
new file mode 100644
index 0000000..56558f3
--- /dev/null
+++ b/include/__format/range_default_formatter.h
@@ -0,0 +1,137 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FORMAT_RANGE_DEFAULT_FORMATTER_H
+#define _LIBCPP___FORMAT_RANGE_DEFAULT_FORMATTER_H
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+#include <__availability>
+#include <__concepts/same_as.h>
+#include <__config>
+#include <__format/concepts.h>
+#include <__format/formatter.h>
+#include <__ranges/concepts.h>
+#include <__type_traits/remove_cvref.h>
+#include <__utility/pair.h>
+#include <tuple>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 20
+
+template <class _Rp, class _CharT>
+concept __const_formattable_range =
+ ranges::input_range<const _Rp> && formattable<ranges::range_reference_t<const _Rp>, _CharT>;
+
+template <class _Rp, class _CharT>
+using __fmt_maybe_const = conditional_t<__const_formattable_range<_Rp, _CharT>, const _Rp, _Rp>;
+
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wshadow")
+_LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wshadow")
+// This shadows map, set, and string.
+enum class range_format { disabled, map, set, sequence, string, debug_string };
+_LIBCPP_DIAGNOSTIC_POP
+
+// There is no definition of this struct, it's purely intended to be used to
+// generate diagnostics.
+template <class _Rp>
+struct _LIBCPP_TEMPLATE_VIS __instantiated_the_primary_template_of_format_kind;
+
+template <class _Rp>
+constexpr range_format format_kind = [] {
+ // [format.range.fmtkind]/1
+ // A program that instantiates the primary template of format_kind is ill-formed.
+ static_assert(sizeof(_Rp) != sizeof(_Rp), "create a template specialization of format_kind for your type");
+ return range_format::disabled;
+}();
+
+template <ranges::input_range _Rp>
+ requires same_as<_Rp, remove_cvref_t<_Rp>>
+inline constexpr range_format format_kind<_Rp> = [] {
+ // [format.range.fmtkind]/2
+
+ // 2.1 If same_as<remove_cvref_t<ranges::range_reference_t<R>>, R> is true,
+ // Otherwise format_kind<R> is range_format::disabled.
+ if constexpr (same_as<remove_cvref_t<ranges::range_reference_t<_Rp>>, _Rp>)
+ return range_format::disabled;
+ // 2.2 Otherwise, if the qualified-id R::key_type is valid and denotes a type:
+ else if constexpr (requires { typename _Rp::key_type; }) {
+ // 2.2.1 If the qualified-id R::mapped_type is valid and denotes a type ...
+ if constexpr (requires { typename _Rp::mapped_type; } &&
+ // 2.2.1 ... If either U is a specialization of pair or U is a specialization
+ // of tuple and tuple_size_v<U> == 2
+ __fmt_pair_like<remove_cvref_t<ranges::range_reference_t<_Rp>>>)
+ return range_format::map;
+ else
+ // 2.2.2 Otherwise format_kind<R> is range_format::set.
+ return range_format::set;
+ } else
+ // 2.3 Otherwise, format_kind<R> is range_format::sequence.
+ return range_format::sequence;
+}();
+
+// This is a non-standard work-around to fix instantiation of
+// formatter<const _CharT[N], _CharT>
+// const _CharT[N] satisfies the ranges::input_range concept.
+// remove_cvref_t<const _CharT[N]> is _CharT[N] so it does not satisfy the
+// requirement of the above specialization. Instead it will instantiate the
+// primary template, which is ill-formed.
+//
+// An alternative solution is to remove the offending formatter.
+//
+// https://godbolt.org/z/bqjhhaexx
+//
+// The removal is proposed in LWG3833, but use the work-around until the issue
+// has been adopted.
+// TODO FMT Implement LWG3833.
+template <class _CharT, size_t N>
+inline constexpr range_format format_kind<const _CharT[N]> = range_format::disabled;
+
+template <range_format _Kp, ranges::input_range _Rp, class _CharT>
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __range_default_formatter;
+
+// Required specializations
+
+template <ranges::input_range _Rp, class _CharT>
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __range_default_formatter<range_format::sequence, _Rp, _CharT> {
+ __range_default_formatter() = delete; // TODO FMT Implement
+};
+
+template <ranges::input_range _Rp, class _CharT>
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __range_default_formatter<range_format::map, _Rp, _CharT> {
+ __range_default_formatter() = delete; // TODO FMT Implement
+};
+
+template <ranges::input_range _Rp, class _CharT>
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __range_default_formatter<range_format::set, _Rp, _CharT> {
+ __range_default_formatter() = delete; // TODO FMT Implement
+};
+
+template <range_format _Kp, ranges::input_range _Rp, class _CharT>
+ requires(_Kp == range_format::string || _Kp == range_format::debug_string)
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT __range_default_formatter<_Kp, _Rp, _CharT> {
+ __range_default_formatter() = delete; // TODO FMT Implement
+};
+
+// Dispatcher to select the specialization based on the type of the range.
+
+template <ranges::input_range _Rp, class _CharT>
+ requires(format_kind<_Rp> != range_format::disabled && formattable<ranges::range_reference_t<_Rp>, _CharT>)
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<_Rp, _CharT>
+ : __range_default_formatter<format_kind<_Rp>, _Rp, _CharT> {};
+
+#endif //_LIBCPP_STD_VER > 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FORMAT_RANGE_DEFAULT_FORMATTER_H
diff --git a/include/__type_traits/is_specialization.h b/include/__type_traits/is_specialization.h
new file mode 100644
index 0000000..0cc3667
--- /dev/null
+++ b/include/__type_traits/is_specialization.h
@@ -0,0 +1,45 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TYPE_TRAITS_IS_SPECIALIZATION
+#define _LIBCPP___TYPE_TRAITS_IS_SPECIALIZATION
+
+// This contains parts of P2098R1 but is based on MSVC STL's implementation.
+//
+// The paper has been rejected
+// We will not pursue P2098R0 (std::is_specialization_of) at this time; we'd
+// like to see a solution to this problem, but it requires language evolution
+// too.
+//
+// Since it is expected a real solution will be provided in the future only the
+// minimal part is implemented.
+//
+// Note a cvref qualified _Tp is never considered a specialization.
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+template <class _Tp, template <class...> class _Template>
+inline constexpr bool __is_specialization_v = false; // true if and only if _Tp is a specialization of _Template
+
+template <template <class...> class _Template, class... _Args>
+inline constexpr bool __is_specialization_v<_Template<_Args...>, _Template> = true;
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_SPECIALIZATION
diff --git a/include/format b/include/format
index 8817dce..e5f8976 100644
--- a/include/format
+++ b/include/format
@@ -112,6 +112,35 @@
using format_parse_context = basic_format_parse_context<char>;
using wformat_parse_context = basic_format_parse_context<wchar_t>;
+ // [format.range], formatting of ranges
+ // [format.range.fmtkind], variable template format_kind
+ enum class range_format { // since C++23
+ disabled,
+ map,
+ set,
+ sequence,
+ string,
+ debug_string
+ };
+
+ template<class R>
+ constexpr unspecified format_kind = unspecified; // since C++23
+
+ template<ranges::input_range R>
+ requires same_as<R, remove_cvref_t<R>>
+ constexpr range_format format_kind<R> = see below; // since C++23
+
+ // [format.range.fmtdef], class template range-default-formatter
+ template<range_format K, ranges::input_range R, class charT>
+ struct range-default-formatter; // exposition only, since C++23
+
+ // [format.range.fmtmap], [format.range.fmtset], [format.range.fmtstr],
+ // specializations for maps, sets, and strings
+ template<ranges::input_range R, class charT>
+ requires (format_kind<R> != range_format::disabled) &&
+ formattable<ranges::range_reference_t<R>, charT>
+ struct formatter<R, charT> : range-default-formatter<format_kind<R>, R, charT> { }; // since C++23
+
// [format.arguments], arguments
// [format.arg], class template basic_format_arg
template<class Context> class basic_format_arg;
@@ -163,6 +192,7 @@
#include <__format/formatter_pointer.h>
#include <__format/formatter_string.h>
#include <__format/parser_std_format_spec.h>
+#include <__format/range_default_formatter.h>
#include <__format/unicode.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 1a33ec2..4033d2f 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -846,6 +846,7 @@
module formatter_pointer { private header "__format/formatter_pointer.h" }
module formatter_string { private header "__format/formatter_string.h" }
module parser_std_format_spec { private header "__format/parser_std_format_spec.h" }
+ module range_default_formatter { private header "__format/range_default_formatter.h" }
module unicode { private header "__format/unicode.h" }
}
}
@@ -1429,6 +1430,7 @@
module is_scoped_enum { private header "__type_traits/is_scoped_enum.h" }
module is_signed { private header "__type_traits/is_signed.h" }
module is_signed_integer { private header "__type_traits/is_signed_integer.h" }
+ module is_specialization { private header "__type_traits/is_specialization.h" }
module is_standard_layout { private header "__type_traits/is_standard_layout.h" }
module is_swappable { private header "__type_traits/is_swappable.h" }
module is_trivial { private header "__type_traits/is_trivial.h" }
diff --git a/include/type_traits b/include/type_traits
index 7587211..757226f 100644
--- a/include/type_traits
+++ b/include/type_traits
@@ -497,6 +497,7 @@
#include <__type_traits/is_scalar.h>
#include <__type_traits/is_scoped_enum.h>
#include <__type_traits/is_signed.h>
+#include <__type_traits/is_specialization.h>
#include <__type_traits/is_standard_layout.h>
#include <__type_traits/is_swappable.h>
#include <__type_traits/is_trivial.h>