[libc++] Granularize <type_traits> includes in <concepts>

[ldionne]

LGTM once you have green CI.

[Mordante]

Thanks for the cleanup! One question.

libcxx/test/libcxx/ranges/range.utility.helpers/different_from.compile.pass.cpp

21

What is the benefit of using a private header here?

[jloser]

libcxx/test/libcxx/ranges/range.utility.helpers/different_from.compile.pass.cpp

21

I assume it's because there is no std::different_from, it's just a useful private concept that we have unit tests for. I'm not sure this is the most appropriate home for these tests nested in ranges/range.utility.helpers as it's more generic than that (isomorphic to std::same_as).

[philnik]

Try to fix CI

libcxx/test/libcxx/ranges/range.utility.helpers/different_from.compile.pass.cpp

21

We check that <__concpet/different_from.h> is self-contained. We might as well, since we test implementation details anyways.

[Mordante]

One request other than that LGTM.

libcxx/test/libcxx/ranges/range.utility.helpers/different_from.compile.pass.cpp

21

We typically don't do that, so IMO it would be good to add a comment like Check that <__concpet/different_from.h> is self-contained.

[philnik]

Address comment

[philnik]

Try to fix CI

[philnik]

Next try

[eaeltsin]

libcxx/include/__type_traits/remove_cvref.h

15

Does the header include itself now?

Can we please remove this?

[Mordante]

libcxx/include/__type_traits/remove_cvref.h

15

Nice catch!

[rtrieu]

libcxx/include/__type_traits/remove_cvref.h

15

I went ahead and removed this in 0c6e74fa744b0e6abe3614af55f4f9dd1fbc54b2.

libcxx/include/__concepts/arithmetic.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_ARITHMETIC_H
 #define _LIBCPP___CONCEPTS_ARITHMETIC_H
 
 #include <__config>
+#include <__type_traits/is_floating_point.h>
+#include <__type_traits/is_integral.h>
+#include <__type_traits/is_signed.h>
 #include <__type_traits/is_signed_integer.h>
 #include <__type_traits/is_unsigned_integer.h>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/assignable.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_ASSIGNABLE_H
 #define _LIBCPP___CONCEPTS_ASSIGNABLE_H
 
 #include <__concepts/common_reference_with.h>
 #include <__concepts/same_as.h>
 #include <__config>
+#include <__type_traits/is_reference.h>
 #include <__type_traits/make_const_lvalue_ref.h>
 #include <__utility/forward.h>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/class_or_enum.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_CLASS_OR_ENUM_H
 #define _LIBCPP___CONCEPTS_CLASS_OR_ENUM_H
 
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_class.h>
+#include <__type_traits/is_enum.h>
+#include <__type_traits/is_union.h>
+#include <__type_traits/remove_cvref.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/common_reference_with.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_COMMON_REFERENCE_WITH_H
 #define _LIBCPP___CONCEPTS_COMMON_REFERENCE_WITH_H
 
 #include <__concepts/convertible_to.h>
 #include <__concepts/same_as.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/common_reference.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/common_with.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_COMMON_WITH_H
 #define _LIBCPP___CONCEPTS_COMMON_WITH_H
 
 #include <__concepts/common_reference_with.h>
 #include <__concepts/same_as.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/add_lvalue_reference.h>
+#include <__type_traits/common_reference.h>
+#include <__type_traits/common_type.h>
+#include <__utility/declval.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/constructible.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_CONSTRUCTIBLE_H
 #define _LIBCPP___CONCEPTS_CONSTRUCTIBLE_H
 
 #include <__concepts/convertible_to.h>
 #include <__concepts/destructible.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_constructible.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/convertible_to.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_CONVERTIBLE_TO_H
 #define _LIBCPP___CONCEPTS_CONVERTIBLE_TO_H
 
 #include <__config>
+#include <__type_traits/is_convertible.h>
 #include <__utility/declval.h>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/derived_from.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_DERIVED_FROM_H
 #define _LIBCPP___CONCEPTS_DERIVED_FROM_H
 
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_base_of.h>
+#include <__type_traits/is_convertible.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/destructible.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_DESTRUCTIBLE_H
 #define _LIBCPP___CONCEPTS_DESTRUCTIBLE_H
 
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_nothrow_destructible.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/different_from.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_DIFFERENT_FROM_H
 #define _LIBCPP___CONCEPTS_DIFFERENT_FROM_H
 
 #include <__concepts/same_as.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/remove_cvref.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/equality_comparable.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_EQUALITY_COMPARABLE_H
 #define _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
 
 #include <__concepts/boolean_testable.h>
 #include <__concepts/common_reference_with.h>
 #include <__config>
+#include <__type_traits/common_reference.h>
 #include <__type_traits/make_const_lvalue_ref.h>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/invocable.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_INVOCABLE_H
 #define _LIBCPP___CONCEPTS_INVOCABLE_H
 
 #include <__config>
 #include <__functional/invoke.h>
 #include <__utility/forward.h>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/movable.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_MOVABLE_H
 #define _LIBCPP___CONCEPTS_MOVABLE_H
 
 #include <__concepts/assignable.h>
 #include <__concepts/constructible.h>
 #include <__concepts/swappable.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_object.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/predicate.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_PREDICATE_H
 #define _LIBCPP___CONCEPTS_PREDICATE_H
 
 #include <__concepts/boolean_testable.h>
 #include <__concepts/invocable.h>
 #include <__config>
-#include <type_traits>
+#include <__functional/invoke.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/same_as.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_SAME_AS_H
 #define _LIBCPP___CONCEPTS_SAME_AS_H
 
 #include <__config>
-#include <type_traits>
+#include <__type_traits/is_same.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/swappable.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_SWAPPABLE_H
 #define _LIBCPP___CONCEPTS_SWAPPABLE_H
 
 #include <__concepts/assignable.h>
 #include <__concepts/class_or_enum.h>
 #include <__concepts/common_reference_with.h>
 #include <__concepts/constructible.h>
 #include <__config>
+#include <__type_traits/extent.h>
+#include <__type_traits/is_nothrow_move_assignable.h>
+#include <__type_traits/is_nothrow_move_constructible.h>
+#include <__type_traits/remove_cvref.h>
 #include <__utility/exchange.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
-#include <type_traits>
+#include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__concepts/totally_ordered.h

 //===----------------------------------------------------------------------===//
 //
 // 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___CONCEPTS_TOTALLY_ORDERED_H
 #define _LIBCPP___CONCEPTS_TOTALLY_ORDERED_H
 
 #include <__concepts/boolean_testable.h>
 #include <__concepts/equality_comparable.h>
 #include <__config>
-#include <type_traits>
+#include <__type_traits/common_reference.h>
+#include <__type_traits/make_const_lvalue_ref.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17

libcxx/include/__type_traits/is_nothrow_constructible.h

 //===----------------------------------------------------------------------===//
 //
 // 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_NOTHROW_CONSTRUCTIBLE_H
 #define _LIBCPP___TYPE_TRAITS_IS_NOTHROW_CONSTRUCTIBLE_H
 
 #include <__config>
 #include <__type_traits/integral_constant.h>
 #include <__type_traits/is_constructible.h>
 #include <__type_traits/is_reference.h>
 #include <__utility/declval.h>
+#include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if __has_builtin(__is_nothrow_constructible)

libcxx/include/__type_traits/is_signed.h

 //===----------------------------------------------------------------------===//
 //
 // 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_SIGNED_H
 #define _LIBCPP___TYPE_TRAITS_IS_SIGNED_H
 
 #include <__config>
 #include <__type_traits/integral_constant.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/is_integral.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if __has_builtin(__is_signed)

libcxx/include/__type_traits/remove_cvref.h

 //===----------------------------------------------------------------------===//
 //
 // 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_REMOVE_CVREF_H
 #define _LIBCPP___TYPE_TRAITS_REMOVE_CVREF_H
 
 #include <__config>
 #include <__type_traits/is_same.h>
 #include <__type_traits/remove_cv.h>
+#include <__type_traits/remove_cvref.h>
 #include <__type_traits/remove_reference.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 

libcxx/include/__utility/swap.h

 //===----------------------------------------------------------------------===//
 //
 // 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___UTILITY_SWAP_H
 #define _LIBCPP___UTILITY_SWAP_H
 
 #include <__config>
+#include <__type_traits/is_move_assignable.h>
+#include <__type_traits/is_move_constructible.h>
+#include <__type_traits/is_nothrow_move_assignable.h>
+#include <__type_traits/is_nothrow_move_constructible.h>
+#include <__type_traits/is_swappable.h>
 #include <__utility/declval.h>
 #include <__utility/move.h>
 #include <cstddef>
-#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_CXX03_LANG

libcxx/include/concepts

 #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 <version>
 
+#if _LIBCPP_STD_VER <= 20 && !defined(_LIPCPP_REMOVE_TRANSITIVE_INCLUDES)
+#  include <type_traits>
+#endif
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 #endif // _LIBCPP_CONCEPTS

libcxx/include/module.modulemap.in

module type_traits {
     module is_object                           { private header "__type_traits/is_object.h" }
     module is_pod                              { private header "__type_traits/is_pod.h" }
     module is_pointer                          { private header "__type_traits/is_pointer.h" }
     module is_polymorphic                      { private header "__type_traits/is_polymorphic.h" }
     module is_primary_template                 { private header "__type_traits/is_primary_template.h" }
     module is_reference                        { private header "__type_traits/is_reference.h" }
     module is_reference_wrapper                { private header "__type_traits/is_reference_wrapper.h" }
     module is_referenceable                    { private header "__type_traits/is_referenceable.h" }
-    module is_same                             { private header "__type_traits/is_same.h" }
+    module is_same                             {
+      private header "__type_traits/is_same.h"
+      export type_traits.integral_constant
+    }
     module is_scalar                           { private header "__type_traits/is_scalar.h" }
     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" }

libcxx/include/sstream

 extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostringstream<char>;
 extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istringstream<char>;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if _LIBCPP_STD_VER <= 20 && !defined(_LIPCPP_REMOVE_TRANSITIVE_INCLUDES)
+#  include <type_traits>
+#endif
+
 #endif // _LIBCPP_SSTREAM

libcxx/test/libcxx/ranges/range.utility.helpers/different_from.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 // <ranges>
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 
-#include <concepts>
+// Check that different_from.h is self-contained
+// ADDITIONAL_COMPILE_FLAGS: -Wno-private-header
 
-#include "test_macros.h"
+#include <__concepts/different_from.h>
 
 static_assert(std::__different_from<int, char>);
 static_assert(std::__different_from<const int, char>);
 static_assert(!std::__different_from<const int, int>);
 static_assert(!std::__different_from<const volatile int, int>);
 static_assert(!std::__different_from<const int&, int>);
 static_assert(!std::__different_from<int&, int>);
 static_assert(!std::__different_from<int&&, int>);
 static_assert(!std::__different_from<int, int&>);
 static_assert(!std::__different_from<int&, const int&>);
 static_assert(!std::__different_from<int(&)(), int()>);
 static_assert(std::__different_from<int(&)(), int(*)()>);
-