[libc++][NFC] Move concepts to a subheader.

[Mordante]

Summary

D103357 added some new concepts. Since the header <concepts> has moved
all its concepts to a separate header these new concepts feel out of
place. Move them to the appropriate header.

[Mordante]

Retrigger CI.

[• Quuxplusone]

libcxx/include/__concepts/arithmetic.h

43–44

__libcpp_floating_point is completely unused, as is __libcpp_is_floating_point. I believe you should just remove those.
Anyone who wants to know whether a type is float/double/long-double should just use the standard std::is_floating_point trait or std::floating_point concept. We have no reason to provide a separate version of our own.

libcxx/include/type_traits

791–792

This comment seems no longer useful. Just remove lines 792-794.

[Mordante]

libcxx/include/__concepts/arithmetic.h

43–44

I added it for consistency, but I don't feel strongly about this concept. I don't like to do that change in this patch. I'll do this in a separate commit.

libcxx/include/type_traits

791–792

Good catch, must have happened when rebasing the original patch.

[Mordante]

Remove outdated comment.

[• Quuxplusone]

LGTM now!

libcxx/include/__concepts/arithmetic.h

 concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
 
 template<class _Tp>
 concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
 
 template<class _Tp>
 concept floating_point = is_floating_point_v<_Tp>;
 
+// Concept helpers for the internal type traits for the fundamental types.
+
+template <class _Tp>
+concept __libcpp_unsigned_integer = __libcpp_is_unsigned_integer<_Tp>::value;
+template <class _Tp>
+concept __libcpp_signed_integer = __libcpp_is_signed_integer<_Tp>::value;
+template <class _Tp>
+concept __libcpp_floating_point = __libcpp_is_floating_point<_Tp>::value;
+
 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___CONCEPTS_ARITHMETIC_H

libcxx/include/__format/format_arg.h

 // -*- 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_FORMAT_ARG_H
 #define _LIBCPP___FORMAT_FORMAT_ARG_H
 
+#include <__concepts/arithmetic.h>
 #include <__config>
 #include <__format/format_error.h>
 #include <__format/format_fwd.h>
 #include <__functional_base>
 #include <__variant/monostate.h>
-#include <concepts>
 #include <string>
 #include <string_view>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS

libcxx/include/concepts

 #include <__concepts/predicate.h>
 #include <__concepts/regular.h>
 #include <__concepts/relation.h>
 #include <__concepts/same_as.h>
 #include <__concepts/semiregular.h>
 #include <__concepts/swappable.h>
 #include <__concepts/totally_ordered.h>
 #include <__config>
-#include <type_traits>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
-
-// Concept helpers for the internal type traits for the fundamental types.
-
-template <class _Tp>
-concept __libcpp_unsigned_integer = __libcpp_is_unsigned_integer<_Tp>::value;
-template <class _Tp>
-concept __libcpp_signed_integer = __libcpp_is_signed_integer<_Tp>::value;
-template <class _Tp>
-concept __libcpp_floating_point = __libcpp_is_floating_point<_Tp>::value;
-
-#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif // _LIBCPP_CONCEPTS

libcxx/include/type_traits

 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_integral_v
     = is_integral<_Tp>::value;
 #endif
 
 #endif // __has_keyword(__is_integral)
 
-// __libcpp_is_signed_integer, __libcpp_is_unsigned_integer
-// <concepts> implements __libcpp_signed_integer, __libcpp_unsigned_integer
-
 // [basic.fundamental] defines five standard signed integer types;
 // __int128_t is an extended signed integer type.
 // The signed and unsigned integer types, plus bool and the
 // five types with "char" in their name, compose the "integral" types.
 
 template <class _Tp> struct __libcpp_is_signed_integer : public false_type {};
 template <> struct __libcpp_is_signed_integer<signed char>      : public true_type {};
 template <> struct __libcpp_is_signed_integer<signed short>     : public true_type {};
 template <> struct __libcpp_is_signed_integer<signed int>       : public true_type {};