diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -99,6 +99,28 @@
   __bsd_locale_fallbacks.h
   __compare/common_comparison_category.h
   __compare/ordering.h
+  __concepts/arithmetic.h
+  __concepts/assignable.h
+  __concepts/boolean_testable.h
+  __concepts/class_or_enum.h
+  __concepts/common_reference_with.h
+  __concepts/common_with.h
+  __concepts/constructible.h
+  __concepts/convertible_to.h
+  __concepts/copyable.h
+  __concepts/derived_from.h
+  __concepts/destructible.h
+  __concepts/different_from.h
+  __concepts/equality_comparable.h
+  __concepts/invocable.h
+  __concepts/movable.h
+  __concepts/predicate.h
+  __concepts/regular.h
+  __concepts/relation.h
+  __concepts/same_as.h
+  __concepts/semiregular.h
+  __concepts/swappable.h
+  __concepts/totally_ordered.h
   __config
   __debug
   __errc
diff --git a/libcxx/include/__concepts/arithmetic.h b/libcxx/include/__concepts/arithmetic.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/arithmetic.h
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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)
+
+// [concepts.arithmetic], arithmetic concepts
+
+template<class _Tp>
+concept integral = is_integral_v<_Tp>;
+
+template<class _Tp>
+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>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_ARITHMETIC_H
diff --git a/libcxx/include/__concepts/assignable.h b/libcxx/include/__concepts/assignable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/assignable.h
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__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 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [concept.assignable]
+
+template<class _Lhs, class _Rhs>
+concept assignable_from =
+  is_lvalue_reference_v<_Lhs> &&
+  common_reference_with<__make_const_lvalue_ref<_Lhs>, __make_const_lvalue_ref<_Rhs>> &&
+  requires (_Lhs __lhs, _Rhs&& __rhs) {
+    { __lhs = _VSTD::forward<_Rhs>(__rhs) } -> same_as<_Lhs>;
+  };
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_ASSIGNABLE_H
diff --git a/libcxx/include/__concepts/boolean_testable.h b/libcxx/include/__concepts/boolean_testable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/boolean_testable.h
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_BOOLEAN_TESTABLE_H
+#define _LIBCPP___CONCEPTS_BOOLEAN_TESTABLE_H
+
+#include <__concepts/convertible_to.h>
+#include <__config>
+
+#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)
+
+// [concepts.booleantestable]
+
+template<class _Tp>
+concept __boolean_testable_impl = convertible_to<_Tp, bool>;
+
+template<class _Tp>
+concept __boolean_testable = __boolean_testable_impl<_Tp> && requires(_Tp&& __t) {
+  { !static_cast<_Tp&&>(__t) } -> __boolean_testable_impl;
+};
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_BOOLEAN_TESTABLE_H
diff --git a/libcxx/include/__concepts/class_or_enum.h b/libcxx/include/__concepts/class_or_enum.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/class_or_enum.h
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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)
+
+// Whether a type is a class type or enumeration type according to the Core wording.
+
+template<class _Tp>
+concept __class_or_enum = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_CLASS_OR_ENUM_H
diff --git a/libcxx/include/__concepts/common_reference_with.h b/libcxx/include/__concepts/common_reference_with.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/common_reference_with.h
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.commonref]
+
+template<class _Tp, class _Up>
+concept common_reference_with =
+  same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>> &&
+  convertible_to<_Tp, common_reference_t<_Tp, _Up>> &&
+  convertible_to<_Up, common_reference_t<_Tp, _Up>>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_COMMON_REFERENCE_WITH_H
diff --git a/libcxx/include/__concepts/common_with.h b/libcxx/include/__concepts/common_with.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/common_with.h
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.common]
+
+template<class _Tp, class _Up>
+concept common_with =
+  same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
+  requires {
+    static_cast<common_type_t<_Tp, _Up>>(declval<_Tp>());
+    static_cast<common_type_t<_Tp, _Up>>(declval<_Up>());
+  } &&
+  common_reference_with<
+    add_lvalue_reference_t<const _Tp>,
+    add_lvalue_reference_t<const _Up>> &&
+  common_reference_with<
+    add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
+    common_reference_t<
+      add_lvalue_reference_t<const _Tp>,
+      add_lvalue_reference_t<const _Up>>>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_COMMON_WITH_H
diff --git a/libcxx/include/__concepts/constructible.h b/libcxx/include/__concepts/constructible.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/constructible.h
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.constructible]
+template<class _Tp, class... _Args>
+concept constructible_from =
+    destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
+
+// [concept.default.init]
+
+template<class _Tp>
+concept __default_initializable = requires { ::new _Tp; };
+
+template<class _Tp>
+concept default_initializable = constructible_from<_Tp> &&
+    requires { _Tp{}; } && __default_initializable<_Tp>;
+
+// [concept.moveconstructible]
+template<class _Tp>
+concept move_constructible =
+  constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
+
+// [concept.copyconstructible]
+template<class _Tp>
+concept copy_constructible =
+  move_constructible<_Tp> &&
+  constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp> &&
+  constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp> &&
+  constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_CONSTRUCTIBLE_H
diff --git a/libcxx/include/__concepts/convertible_to.h b/libcxx/include/__concepts/convertible_to.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/convertible_to.h
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.convertible]
+
+template<class _From, class _To>
+concept convertible_to =
+  is_convertible_v<_From, _To> &&
+  requires (add_rvalue_reference_t<_From> (&__f)()) {
+    static_cast<_To>(__f());
+  };
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_CONVERTIBLE_TO_H
diff --git a/libcxx/include/__concepts/copyable.h b/libcxx/include/__concepts/copyable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/copyable.h
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COPYABLE_H
+#define _LIBCPP___CONCEPTS_COPYABLE_H
+
+#include <__concepts/assignable.h>
+#include <__concepts/constructible.h>
+#include <__concepts/movable.h>
+#include <__config>
+
+#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)
+
+// [concepts.object]
+
+template<class _Tp>
+concept copyable =
+  copy_constructible<_Tp> &&
+  movable<_Tp> &&
+  assignable_from<_Tp&, _Tp&> &&
+  assignable_from<_Tp&, const _Tp&> &&
+  assignable_from<_Tp&, const _Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_COPYABLE_H
diff --git a/libcxx/include/__concepts/derived_from.h b/libcxx/include/__concepts/derived_from.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/derived_from.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.derived]
+
+template<class _Dp, class _Bp>
+concept derived_from =
+  is_base_of_v<_Bp, _Dp> &&
+  is_convertible_v<const volatile _Dp*, const volatile _Bp*>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_DERIVED_FROM_H
diff --git a/libcxx/include/__concepts/destructible.h b/libcxx/include/__concepts/destructible.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/destructible.h
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.destructible]
+
+template<class _Tp>
+concept destructible = is_nothrow_destructible_v<_Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_DESTRUCTIBLE_H
diff --git a/libcxx/include/__concepts/different_from.h b/libcxx/include/__concepts/different_from.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/different_from.h
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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)
+
+template<class _Tp, class _Up>
+concept __different_from = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_DIFFERENT_FROM_H
diff --git a/libcxx/include/__concepts/equality_comparable.h b/libcxx/include/__concepts/equality_comparable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/equality_comparable.h
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.equalitycomparable]
+
+template<class _Tp, class _Up>
+concept __weakly_equality_comparable_with =
+  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
+    { __t == __u } -> __boolean_testable;
+    { __t != __u } -> __boolean_testable;
+    { __u == __t } -> __boolean_testable;
+    { __u != __t } -> __boolean_testable;
+  };
+
+template<class _Tp>
+concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;
+
+template<class _Tp, class _Up>
+concept equality_comparable_with =
+  equality_comparable<_Tp> && equality_comparable<_Up> &&
+  common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
+  equality_comparable<
+    common_reference_t<
+      __make_const_lvalue_ref<_Tp>,
+      __make_const_lvalue_ref<_Up>>> &&
+  __weakly_equality_comparable_with<_Tp, _Up>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
diff --git a/libcxx/include/__concepts/invocable.h b/libcxx/include/__concepts/invocable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/invocable.h
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [concept.invocable]
+
+template<class _Fn, class... _Args>
+concept invocable = requires(_Fn&& __fn, _Args&&... __args) {
+  _VSTD::invoke(_VSTD::forward<_Fn>(__fn), _VSTD::forward<_Args>(__args)...); // not required to be equality preserving
+};
+
+// [concept.regular.invocable]
+
+template<class _Fn, class... _Args>
+concept regular_invocable = invocable<_Fn, _Args...>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_INVOCABLE_H
diff --git a/libcxx/include/__concepts/movable.h b/libcxx/include/__concepts/movable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/movable.h
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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)
+
+// [concepts.object]
+
+template<class _Tp>
+concept movable =
+  is_object_v<_Tp> &&
+  move_constructible<_Tp> &&
+  assignable_from<_Tp&, _Tp> &&
+  swappable<_Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_MOVABLE_H
diff --git a/libcxx/include/__concepts/predicate.h b/libcxx/include/__concepts/predicate.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/predicate.h
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.predicate]
+
+template<class _Fn, class... _Args>
+concept predicate =
+  regular_invocable<_Fn, _Args...> && __boolean_testable<invoke_result_t<_Fn, _Args...>>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_PREDICATE_H
diff --git a/libcxx/include/__concepts/regular.h b/libcxx/include/__concepts/regular.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/regular.h
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_REGULAR_H
+#define _LIBCPP___CONCEPTS_REGULAR_H
+
+#include <__concepts/equality_comparable.h>
+#include <__concepts/semiregular.h>
+#include <__config>
+
+#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.object]
+
+template<class _Tp>
+concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_REGULAR_H
diff --git a/libcxx/include/__concepts/relation.h b/libcxx/include/__concepts/relation.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/relation.h
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_RELATION_H
+#define _LIBCPP___CONCEPTS_RELATION_H
+
+#include <__concepts/predicate.h>
+#include <__config>
+
+#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.relation]
+
+template<class _Rp, class _Tp, class _Up>
+concept relation =
+  predicate<_Rp, _Tp, _Tp> && predicate<_Rp, _Up, _Up> &&
+  predicate<_Rp, _Tp, _Up> && predicate<_Rp, _Up, _Tp>;
+
+// [concept.equiv]
+
+template<class _Rp, class _Tp, class _Up>
+concept equivalence_relation = relation<_Rp, _Tp, _Up>;
+
+// [concept.strictweakorder]
+
+template<class _Rp, class _Tp, class _Up>
+concept strict_weak_order = relation<_Rp, _Tp, _Up>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_RELATION_H
diff --git a/libcxx/include/__concepts/same_as.h b/libcxx/include/__concepts/same_as.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/same_as.h
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.same]
+
+template<class _Tp, class _Up>
+concept __same_as_impl = _IsSame<_Tp, _Up>::value;
+
+template<class _Tp, class _Up>
+concept same_as = __same_as_impl<_Tp, _Up> && __same_as_impl<_Up, _Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_SAME_AS_H
diff --git a/libcxx/include/__concepts/semiregular.h b/libcxx/include/__concepts/semiregular.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/semiregular.h
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_SEMIREGULAR_H
+#define _LIBCPP___CONCEPTS_SEMIREGULAR_H
+
+#include <__concepts/constructible.h>
+#include <__concepts/copyable.h>
+#include <__config>
+
+#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.object]
+
+template<class _Tp>
+concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_SEMIREGULAR_H
diff --git a/libcxx/include/__concepts/swappable.h b/libcxx/include/__concepts/swappable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/swappable.h
@@ -0,0 +1,115 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__utility/exchange.h>
+#include <__utility/forward.h>
+#include <__utility/move.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 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [concept.swappable]
+namespace ranges::__swap {
+  // Deleted to inhibit ADL
+  template<class _Tp>
+  void swap(_Tp&, _Tp&) = delete;
+
+
+  // [1]
+  template<class _Tp, class _Up>
+  concept __unqualified_swappable_with =
+    (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
+    requires(_Tp&& __t, _Up&& __u) {
+      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    };
+
+  struct __fn;
+
+  template<class _Tp, class _Up, size_t _Size>
+  concept __swappable_arrays =
+    !__unqualified_swappable_with<_Tp(&)[_Size], _Up(&)[_Size]> &&
+    extent_v<_Tp> == extent_v<_Up> &&
+    requires(_Tp(& __t)[_Size], _Up(& __u)[_Size], const __fn& __swap) {
+      __swap(__t[0], __u[0]);
+    };
+
+  template<class _Tp>
+  concept __exchangeable =
+    !__unqualified_swappable_with<_Tp&, _Tp&> &&
+    move_constructible<_Tp> &&
+    assignable_from<_Tp&, _Tp>;
+
+  struct __fn {
+    // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
+    // *The name `swap` is used here unqualified.
+    template<class _Tp, class _Up>
+      requires __unqualified_swappable_with<_Tp, _Up>
+    constexpr void operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+    {
+      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    }
+
+    // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
+    template<class _Tp, class _Up, size_t _Size>
+      requires __swappable_arrays<_Tp, _Up, _Size>
+    constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
+      noexcept(noexcept((*this)(*__t, *__u)))
+    {
+      // TODO(cjdb): replace with `ranges::swap_ranges`.
+      for (size_t __i = 0; __i < _Size; ++__i) {
+        (*this)(__t[__i], __u[__i]);
+      }
+    }
+
+    // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
+    template<__exchangeable _Tp>
+    constexpr void operator()(_Tp& __x, _Tp& __y) const
+      noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>)
+    {
+      __y = _VSTD::exchange(__x, _VSTD::move(__y));
+    }
+  };
+} // namespace ranges::__swap
+
+namespace ranges::inline __cpo {
+  inline constexpr auto swap = __swap::__fn{};
+} // namespace ranges::__cpo
+
+template<class _Tp>
+concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
+
+template<class _Tp, class _Up>
+concept swappable_with =
+  common_reference_with<_Tp, _Up> &&
+  requires(_Tp&& __t, _Up&& __u) {
+    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Tp>(__t));
+    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Up>(__u));
+    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Tp>(__t));
+  };
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_SWAPPABLE_H
diff --git a/libcxx/include/__concepts/totally_ordered.h b/libcxx/include/__concepts/totally_ordered.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__concepts/totally_ordered.h
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+
+#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.totallyordered]
+
+template<class _Tp, class _Up>
+concept __partially_ordered_with =
+  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
+    { __t <  __u } -> __boolean_testable;
+    { __t >  __u } -> __boolean_testable;
+    { __t <= __u } -> __boolean_testable;
+    { __t >= __u } -> __boolean_testable;
+    { __u <  __t } -> __boolean_testable;
+    { __u >  __t } -> __boolean_testable;
+    { __u <= __t } -> __boolean_testable;
+    { __u >= __t } -> __boolean_testable;
+  };
+
+template<class _Tp>
+concept totally_ordered = equality_comparable<_Tp> && __partially_ordered_with<_Tp, _Tp>;
+
+template<class _Tp, class _Up>
+concept totally_ordered_with =
+  totally_ordered<_Tp> && totally_ordered<_Up> &&
+  equality_comparable_with<_Tp, _Up> &&
+  totally_ordered<
+    common_reference_t<
+      __make_const_lvalue_ref<_Tp>,
+      __make_const_lvalue_ref<_Up>>> &&
+  __partially_ordered_with<_Tp, _Up>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CONCEPTS_TOTALLY_ORDERED_H
diff --git a/libcxx/include/concepts b/libcxx/include/concepts
--- a/libcxx/include/concepts
+++ b/libcxx/include/concepts
@@ -1,5 +1,5 @@
 // -*- C++ -*-
-//===-------------------------- concepts ----------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -129,327 +129,33 @@
 
 */
 
+#include <__concepts/arithmetic.h>
+#include <__concepts/assignable.h>
+#include <__concepts/boolean_testable.h>
+#include <__concepts/class_or_enum.h>
+#include <__concepts/common_reference_with.h>
+#include <__concepts/common_with.h>
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/copyable.h>
+#include <__concepts/derived_from.h>
+#include <__concepts/destructible.h>
+#include <__concepts/different_from.h>
+#include <__concepts/equality_comparable.h>
+#include <__concepts/invocable.h>
+#include <__concepts/movable.h>
+#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 <__functional/invoke.h>
-#include <__functional_base>
-#include <type_traits>
-#include <utility>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
-
-// [concept.same]
-
-template<class _Tp, class _Up>
-concept __same_as_impl = _IsSame<_Tp, _Up>::value;
-
-template<class _Tp, class _Up>
-concept same_as = __same_as_impl<_Tp, _Up> && __same_as_impl<_Up, _Tp>;
-
-// [concept.derived]
-template<class _Dp, class _Bp>
-concept derived_from =
-  is_base_of_v<_Bp, _Dp> &&
-  is_convertible_v<const volatile _Dp*, const volatile _Bp*>;
-
-// [concept.convertible]
-template<class _From, class _To>
-concept convertible_to =
-  is_convertible_v<_From, _To> &&
-  requires(add_rvalue_reference_t<_From> (&__f)()) {
-    static_cast<_To>(__f());
-  };
-
-// [concept.commonref]
-template<class _Tp, class _Up>
-concept common_reference_with =
-  same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>> &&
-  convertible_to<_Tp, common_reference_t<_Tp, _Up>> &&
-  convertible_to<_Up, common_reference_t<_Tp, _Up>>;
-
-// [concept.common]
-template<class _Tp, class _Up>
-concept common_with =
-  same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
-  requires {
-    static_cast<common_type_t<_Tp, _Up>>(declval<_Tp>());
-    static_cast<common_type_t<_Tp, _Up>>(declval<_Up>());
-  } &&
-  common_reference_with<
-    add_lvalue_reference_t<const _Tp>,
-    add_lvalue_reference_t<const _Up>> &&
-  common_reference_with<
-    add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
-    common_reference_t<
-      add_lvalue_reference_t<const _Tp>,
-      add_lvalue_reference_t<const _Up>>>;
-
-// [concepts.arithmetic], arithmetic concepts
-template<class _Tp>
-concept integral = is_integral_v<_Tp>;
-
-template<class _Tp>
-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.assignable]
-template<class _Lhs, class _Rhs>
-concept assignable_from =
-  is_lvalue_reference_v<_Lhs> &&
-  common_reference_with<__make_const_lvalue_ref<_Lhs>, __make_const_lvalue_ref<_Rhs>> &&
-  requires (_Lhs __lhs, _Rhs&& __rhs) {
-    { __lhs = _VSTD::forward<_Rhs>(__rhs) } -> same_as<_Lhs>;
-  };
-
-// [concept.destructible]
-
-template<class _Tp>
-concept destructible = is_nothrow_destructible_v<_Tp>;
-
-// [concept.constructible]
-template<class _Tp, class... _Args>
-concept constructible_from =
-    destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
-
-// [concept.default.init]
-
-template<class _Tp>
-concept __default_initializable = requires { ::new _Tp; };
-
-template<class _Tp>
-concept default_initializable = constructible_from<_Tp> &&
-    requires { _Tp{}; } && __default_initializable<_Tp>;
-
-// [concept.moveconstructible]
-template<class _Tp>
-concept move_constructible =
-  constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
-
-// [concept.copyconstructible]
-template<class _Tp>
-concept copy_constructible =
-  move_constructible<_Tp> &&
-  constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp> &&
-  constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp> &&
-  constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
-
-// Whether a type is a class type or enumeration type according to the Core wording.
-template<class _Tp>
-concept __class_or_enum = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
-
-// [concept.swappable]
-namespace ranges::__swap {
-  // Deleted to inhibit ADL
-  template<class _Tp>
-  void swap(_Tp&, _Tp&) = delete;
-
-
-  // [1]
-  template<class _Tp, class _Up>
-  concept __unqualified_swappable_with =
-    (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
-    requires(_Tp&& __t, _Up&& __u) {
-      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
-    };
-
-  struct __fn;
-
-  template<class _Tp, class _Up, size_t _Size>
-  concept __swappable_arrays =
-    !__unqualified_swappable_with<_Tp(&)[_Size], _Up(&)[_Size]> &&
-    extent_v<_Tp> == extent_v<_Up> &&
-    requires(_Tp(& __t)[_Size], _Up(& __u)[_Size], const __fn& __swap) {
-      __swap(__t[0], __u[0]);
-    };
-
-  template<class _Tp>
-  concept __exchangeable =
-    !__unqualified_swappable_with<_Tp&, _Tp&> &&
-    move_constructible<_Tp> &&
-    assignable_from<_Tp&, _Tp>;
-
-  struct __fn {
-    // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
-    // *The name `swap` is used here unqualified.
-    template<class _Tp, class _Up>
-    requires __unqualified_swappable_with<_Tp, _Up>
-    constexpr void operator()(_Tp&& __t, _Up&& __u) const
-    noexcept(noexcept(swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
-    {
-      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
-    }
-
-    // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
-    template<class _Tp, class _Up, size_t _Size>
-    requires __swappable_arrays<_Tp, _Up, _Size>
-    constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
-    noexcept(noexcept((*this)(*__t, *__u)))
-    {
-      // TODO(cjdb): replace with `ranges::swap_ranges`.
-      for (size_t __i = 0; __i < _Size; ++__i) {
-        (*this)(__t[__i], __u[__i]);
-      }
-    }
-
-    // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
-    template<__exchangeable _Tp>
-    constexpr void operator()(_Tp& __x, _Tp& __y) const
-    noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>)
-    {
-      __y = _VSTD::exchange(__x, _VSTD::move(__y));
-    }
-  };
-} // namespace ranges::__swap
-
-namespace ranges::inline __cpo {
-  inline constexpr auto swap = __swap::__fn{};
-} // namespace ranges::__cpo
-
-template<class _Tp>
-concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
-
-template<class _Tp, class _Up>
-concept swappable_with =
-  common_reference_with<_Tp, _Up> &&
-  requires(_Tp&& __t, _Up&& __u) {
-    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Tp>(__t));
-    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Up>(__u));
-    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
-    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Tp>(__t));
-  };
-
-// [concept.booleantestable]
-template<class _Tp>
-concept __boolean_testable_impl = convertible_to<_Tp, bool>;
-
-template<class _Tp>
-concept __boolean_testable = __boolean_testable_impl<_Tp> && requires(_Tp&& __t) {
-  { !std::forward<_Tp>(__t) } -> __boolean_testable_impl;
-};
-
-// [concept.equalitycomparable]
-template<class _Tp, class _Up>
-concept __weakly_equality_comparable_with =
-  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
-    { __t == __u } -> __boolean_testable;
-    { __t != __u } -> __boolean_testable;
-    { __u == __t } -> __boolean_testable;
-    { __u != __t } -> __boolean_testable;
-  };
-
-template<class _Tp>
-concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;
-
-template<class _Tp, class _Up>
-concept equality_comparable_with =
-  equality_comparable<_Tp> && equality_comparable<_Up> &&
-  common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
-  equality_comparable<
-    common_reference_t<
-      __make_const_lvalue_ref<_Tp>,
-      __make_const_lvalue_ref<_Up>>> &&
-  __weakly_equality_comparable_with<_Tp, _Up>;
-
-// [concept.totallyordered]
-
-template<class _Tp, class _Up>
-concept __partially_ordered_with =
-  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
-    { __t <  __u } -> __boolean_testable;
-    { __t >  __u } -> __boolean_testable;
-    { __t <= __u } -> __boolean_testable;
-    { __t >= __u } -> __boolean_testable;
-    { __u <  __t } -> __boolean_testable;
-    { __u >  __t } -> __boolean_testable;
-    { __u <= __t } -> __boolean_testable;
-    { __u >= __t } -> __boolean_testable;
-  };
-
-template<class _Tp>
-concept totally_ordered = equality_comparable<_Tp> && __partially_ordered_with<_Tp, _Tp>;
-
-template<class _Tp, class _Up>
-concept totally_ordered_with =
-  totally_ordered<_Tp> && totally_ordered<_Up> &&
-  equality_comparable_with<_Tp, _Up> &&
-  totally_ordered<
-    common_reference_t<
-      __make_const_lvalue_ref<_Tp>,
-      __make_const_lvalue_ref<_Up>>> &&
-  __partially_ordered_with<_Tp, _Up>;
-
-// [concepts.object]
-template<class _Tp>
-concept movable =
-  is_object_v<_Tp> &&
-  move_constructible<_Tp> &&
-  assignable_from<_Tp&, _Tp> &&
-  swappable<_Tp>;
-
-template<class _Tp>
-concept copyable =
-  copy_constructible<_Tp> &&
-  movable<_Tp> &&
-  assignable_from<_Tp&, _Tp&> &&
-  assignable_from<_Tp&, const _Tp&> &&
-  assignable_from<_Tp&, const _Tp>;
-
-template<class _Tp>
-concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
-
-template<class _Tp>
-concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
-
-// [concept.invocable]
-template<class _Fn, class... _Args>
-concept invocable = requires(_Fn&& __fn, _Args&&... __args) {
-  _VSTD::invoke(_VSTD::forward<_Fn>(__fn), _VSTD::forward<_Args>(__args)...); // not required to be equality preserving
-};
-
-// [concept.regular.invocable]
-template<class _Fn, class... _Args>
-concept regular_invocable = invocable<_Fn, _Args...>;
-
-// [concept.predicate]
-template<class _Fn, class... _Args>
-concept predicate =
-  regular_invocable<_Fn, _Args...> && __boolean_testable<invoke_result_t<_Fn, _Args...>>;
-
-// [concept.relation]
-template<class _Rp, class _Tp, class _Up>
-concept relation =
-  predicate<_Rp, _Tp, _Tp> && predicate<_Rp, _Up, _Up> &&
-  predicate<_Rp, _Tp, _Up> && predicate<_Rp, _Up, _Tp>;
-
-// [concept.equiv]
-template<class _Rp, class _Tp, class _Up>
-concept equivalence_relation = relation<_Rp, _Tp, _Up>;
-
-// [concept.strictweakorder]
-template<class _Rp, class _Tp, class _Up>
-concept strict_weak_order = relation<_Rp, _Tp, _Up>;
-
-template<class _Tp, class _Up>
-concept __different_from = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
-
-#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
-
-_LIBCPP_END_NAMESPACE_STD
-
-_LIBCPP_POP_MACROS
-
 #endif // _LIBCPP_CONCEPTS
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -371,6 +371,31 @@
   module concepts {
     header "concepts"
     export *
+
+    module __concepts {
+      module arithmetic                 { private header "__concepts/arithmetic.h"                }
+      module assignable                 { private header "__concepts/assignable.h"                }
+      module boolean_testable           { private header "__concepts/boolean_testable.h"          }
+      module class_or_enum              { private header "__concepts/class_or_enum.h"             }
+      module common_reference_with      { private header "__concepts/common_reference_with.h"     }
+      module common_with                { private header "__concepts/common_with.h"               }
+      module constructible              { private header "__concepts/constructible.h"             }
+      module convertible_to             { private header "__concepts/convertible_to.h"            }
+      module copyable                   { private header "__concepts/copyable.h"                  }
+      module derived_from               { private header "__concepts/derived_from.h"              }
+      module destructible               { private header "__concepts/destructible.h"              }
+      module different_from             { private header "__concepts/different_from.h"            }
+      module equality_comparable        { private header "__concepts/equality_comparable.h"       }
+      module invocable                  { private header "__concepts/invocable.h"                 }
+      module movable                    { private header "__concepts/movable.h"                   }
+      module predicate                  { private header "__concepts/predicate.h"                 }
+      module regular                    { private header "__concepts/regular.h"                   }
+      module relation                   { private header "__concepts/relation.h"                  }
+      module same_as                    { private header "__concepts/same_as.h"                   }
+      module semiregular                { private header "__concepts/semiregular.h"               }
+      module swappable                  { private header "__concepts/swappable.h"                 }
+      module totally_ordered            { private header "__concepts/totally_ordered.h"           }
+    }
   }
   module condition_variable {
     header "condition_variable"
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/arithmetic.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/arithmetic.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/arithmetic.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/arithmetic.h'}}
+#include <__concepts/arithmetic.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/assignable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/assignable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/assignable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/assignable.h'}}
+#include <__concepts/assignable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/boolean_testable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/boolean_testable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/boolean_testable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/boolean_testable.h'}}
+#include <__concepts/boolean_testable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/class_or_enum.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/class_or_enum.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/class_or_enum.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/class_or_enum.h'}}
+#include <__concepts/class_or_enum.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_reference_with.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_reference_with.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_reference_with.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/common_reference_with.h'}}
+#include <__concepts/common_reference_with.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_with.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_with.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/common_with.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/common_with.h'}}
+#include <__concepts/common_with.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/constructible.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/constructible.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/constructible.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/constructible.h'}}
+#include <__concepts/constructible.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/convertible_to.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/convertible_to.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/convertible_to.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/convertible_to.h'}}
+#include <__concepts/convertible_to.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/copyable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/copyable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/copyable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/copyable.h'}}
+#include <__concepts/copyable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/derived_from.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/derived_from.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/derived_from.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/derived_from.h'}}
+#include <__concepts/derived_from.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/destructible.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/destructible.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/destructible.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/destructible.h'}}
+#include <__concepts/destructible.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/different_from.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/different_from.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/different_from.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/different_from.h'}}
+#include <__concepts/different_from.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/equality_comparable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/equality_comparable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/equality_comparable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/equality_comparable.h'}}
+#include <__concepts/equality_comparable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/invocable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/invocable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/invocable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/invocable.h'}}
+#include <__concepts/invocable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/movable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/movable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/movable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/movable.h'}}
+#include <__concepts/movable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/predicate.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/predicate.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/predicate.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/predicate.h'}}
+#include <__concepts/predicate.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/regular.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/regular.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/regular.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/regular.h'}}
+#include <__concepts/regular.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/relation.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/relation.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/relation.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/relation.h'}}
+#include <__concepts/relation.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/same_as.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/same_as.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/same_as.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/same_as.h'}}
+#include <__concepts/same_as.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/semiregular.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/semiregular.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/semiregular.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/semiregular.h'}}
+#include <__concepts/semiregular.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/swappable.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/swappable.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/swappable.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/swappable.h'}}
+#include <__concepts/swappable.h>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/concepts/totally_ordered.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/totally_ordered.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/concepts/totally_ordered.module.verify.cpp
@@ -0,0 +1,16 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__concepts/totally_ordered.h'}}
+#include <__concepts/totally_ordered.h>