diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -324,6 +324,8 @@
   __functional/unary_negate.h
   __functional/unwrap_ref.h
   __functional/weak_result_type.h
+  __fwd/hash.h
+  __fwd/pair.h
   __fwd/span.h
   __fwd/string_view.h
   __hash_table
@@ -509,6 +511,7 @@
   __type_traits/aligned_union.h
   __type_traits/alignment_of.h
   __type_traits/apply_cv.h
+  __type_traits/can_extract_key.h
   __type_traits/common_reference.h
   __type_traits/common_type.h
   __type_traits/conditional.h
@@ -516,6 +519,7 @@
   __type_traits/copy_cv.h
   __type_traits/copy_cvref.h
   __type_traits/decay.h
+  __type_traits/dependent_type.h
   __type_traits/disjunction.h
   __type_traits/enable_if.h
   __type_traits/extent.h
@@ -530,6 +534,7 @@
   __type_traits/is_base_of.h
   __type_traits/is_bounded_array.h
   __type_traits/is_callable.h
+  __type_traits/is_char_like_type.h
   __type_traits/is_class.h
   __type_traits/is_compound.h
   __type_traits/is_const.h
@@ -547,6 +552,7 @@
   __type_traits/is_floating_point.h
   __type_traits/is_function.h
   __type_traits/is_fundamental.h
+  __type_traits/is_implicitly_default_constructible.h
   __type_traits/is_integral.h
   __type_traits/is_literal_type.h
   __type_traits/is_member_function_pointer.h
@@ -578,6 +584,7 @@
   __type_traits/is_signed.h
   __type_traits/is_signed_integer.h
   __type_traits/is_standard_layout.h
+  __type_traits/is_swappable.h
   __type_traits/is_trivial.h
   __type_traits/is_trivially_assignable.h
   __type_traits/is_trivially_constructible.h
@@ -597,20 +604,24 @@
   __type_traits/is_volatile.h
   __type_traits/lazy.h
   __type_traits/make_32_64_or_128_bit.h
+  __type_traits/make_const_lvalue_ref.h
   __type_traits/make_signed.h
   __type_traits/make_unsigned.h
+  __type_traits/maybe_const.h
   __type_traits/nat.h
   __type_traits/negation.h
   __type_traits/promote.h
   __type_traits/rank.h
   __type_traits/remove_all_extents.h
   __type_traits/remove_const.h
+  __type_traits/remove_const_ref.h
   __type_traits/remove_cv.h
   __type_traits/remove_cvref.h
   __type_traits/remove_extent.h
   __type_traits/remove_pointer.h
   __type_traits/remove_reference.h
   __type_traits/remove_volatile.h
+  __type_traits/result_of.h
   __type_traits/type_identity.h
   __type_traits/type_list.h
   __type_traits/underlying_type.h
@@ -619,6 +630,7 @@
   __utility/as_const.h
   __utility/auto_cast.h
   __utility/cmp.h
+  __utility/convert_to_integral.h
   __utility/declval.h
   __utility/exchange.h
   __utility/forward.h
diff --git a/libcxx/include/__algorithm/copy_n.h b/libcxx/include/__algorithm/copy_n.h
--- a/libcxx/include/__algorithm/copy_n.h
+++ b/libcxx/include/__algorithm/copy_n.h
@@ -12,6 +12,7 @@
 #include <__algorithm/copy.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
+#include <__utility/convert_to_integral.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__algorithm/fill_n.h b/libcxx/include/__algorithm/fill_n.h
--- a/libcxx/include/__algorithm/fill_n.h
+++ b/libcxx/include/__algorithm/fill_n.h
@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__iterator/iterator_traits.h>
+#include <__utility/convert_to_integral.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__algorithm/for_each_n.h b/libcxx/include/__algorithm/for_each_n.h
--- a/libcxx/include/__algorithm/for_each_n.h
+++ b/libcxx/include/__algorithm/for_each_n.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___ALGORITHM_FOR_EACH_N_H
 
 #include <__config>
+#include <__utility/convert_to_integral.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__algorithm/generate_n.h b/libcxx/include/__algorithm/generate_n.h
--- a/libcxx/include/__algorithm/generate_n.h
+++ b/libcxx/include/__algorithm/generate_n.h
@@ -10,6 +10,7 @@
 #define _LIBCPP___ALGORITHM_GENERATE_N_H
 
 #include <__config>
+#include <__utility/convert_to_integral.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__algorithm/search_n.h b/libcxx/include/__algorithm/search_n.h
--- a/libcxx/include/__algorithm/search_n.h
+++ b/libcxx/include/__algorithm/search_n.h
@@ -19,6 +19,7 @@
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/concepts.h>
+#include <__utility/convert_to_integral.h>
 #include <__utility/pair.h>
 #include <type_traits>  // __convert_to_integral
 
diff --git a/libcxx/include/__compare/compare_three_way_result.h b/libcxx/include/__compare/compare_three_way_result.h
--- a/libcxx/include/__compare/compare_three_way_result.h
+++ b/libcxx/include/__compare/compare_three_way_result.h
@@ -10,6 +10,7 @@
 #define _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
 
 #include <__config>
+#include <__type_traits/make_const_lvalue_ref.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__compare/three_way_comparable.h b/libcxx/include/__compare/three_way_comparable.h
--- a/libcxx/include/__compare/three_way_comparable.h
+++ b/libcxx/include/__compare/three_way_comparable.h
@@ -16,6 +16,7 @@
 #include <__concepts/same_as.h>
 #include <__concepts/totally_ordered.h>
 #include <__config>
+#include <__type_traits/make_const_lvalue_ref.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__concepts/assignable.h b/libcxx/include/__concepts/assignable.h
--- a/libcxx/include/__concepts/assignable.h
+++ b/libcxx/include/__concepts/assignable.h
@@ -12,6 +12,7 @@
 #include <__concepts/common_reference_with.h>
 #include <__concepts/same_as.h>
 #include <__config>
+#include <__type_traits/make_const_lvalue_ref.h>
 #include <__utility/forward.h>
 #include <type_traits>
 
diff --git a/libcxx/include/__concepts/equality_comparable.h b/libcxx/include/__concepts/equality_comparable.h
--- a/libcxx/include/__concepts/equality_comparable.h
+++ b/libcxx/include/__concepts/equality_comparable.h
@@ -12,6 +12,7 @@
 #include <__concepts/boolean_testable.h>
 #include <__concepts/common_reference_with.h>
 #include <__config>
+#include <__type_traits/make_const_lvalue_ref.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__functional/hash.h b/libcxx/include/__functional/hash.h
--- a/libcxx/include/__functional/hash.h
+++ b/libcxx/include/__functional/hash.h
@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__functional/unary_function.h>
+#include <__fwd/hash.h>
 #include <__tuple>
 #include <__utility/forward.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__fwd/hash.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__fwd/hash.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__fwd/hash.h
@@ -1,4 +1,3 @@
-// -*- C++ -*-
 //===---------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -7,31 +6,20 @@
 //
 //===---------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___FWD_SPAN_H
+#define _LIBCPP___FWD_SPAN_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template <class>
+struct _LIBCPP_TEMPLATE_VIS hash;
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___FWD_SPAN_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__fwd/pair.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__fwd/pair.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__fwd/pair.h
@@ -1,4 +1,3 @@
-// -*- C++ -*-
 //===---------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -7,31 +6,20 @@
 //
 //===---------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___FWD_PAIR_H
+#define _LIBCPP___FWD_PAIR_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template <class, class>
+struct _LIBCPP_TEMPLATE_VIS pair;
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___FWD_PAIR_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__fwd/span.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__fwd/span.h
@@ -7,8 +7,8 @@
 //
 //===---------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___FWD_HASH_H
+#define _LIBCPP___FWD_HASH_H
 
 #include <__config>
 #include <cstddef>
@@ -34,4 +34,4 @@
 
 _LIBCPP_POP_MACROS
 
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___FWD_HASH_H
diff --git a/libcxx/include/__fwd/string_view.h b/libcxx/include/__fwd/string_view.h
--- a/libcxx/include/__fwd/string_view.h
+++ b/libcxx/include/__fwd/string_view.h
@@ -7,8 +7,8 @@
 //
 //===---------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_STRING_VIEW_H
-#define _LIBCPP_FWD_STRING_VIEW_H
+#ifndef _LIBCPP___FWD_STRING_VIEW_H
+#define _LIBCPP___FWD_STRING_VIEW_H
 
 #include <__config>
 #include <iosfwd> // char_traits
@@ -34,4 +34,4 @@
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP_FWD_STRING_VIEW_H
+#endif // _LIBCPP___FWD_STRING_VIEW_H
diff --git a/libcxx/include/__hash_table b/libcxx/include/__hash_table
--- a/libcxx/include/__hash_table
+++ b/libcxx/include/__hash_table
@@ -18,6 +18,7 @@
 #include <__debug>
 #include <__functional/hash.h>
 #include <__iterator/iterator_traits.h>
+#include <__type_traits/can_extract_key.h>
 #include <__utility/swap.h>
 #include <cmath>
 #include <initializer_list>
diff --git a/libcxx/include/__iterator/advance.h b/libcxx/include/__iterator/advance.h
--- a/libcxx/include/__iterator/advance.h
+++ b/libcxx/include/__iterator/advance.h
@@ -15,6 +15,7 @@
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
 #include <__iterator/iterator_traits.h>
+#include <__utility/convert_to_integral.h>
 #include <__utility/move.h>
 #include <__utility/unreachable.h>
 #include <concepts>
diff --git a/libcxx/include/__iterator/iterator_traits.h b/libcxx/include/__iterator/iterator_traits.h
--- a/libcxx/include/__iterator/iterator_traits.h
+++ b/libcxx/include/__iterator/iterator_traits.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
 
 #include <__config>
+#include <__fwd/pair.h>
 #include <__iterator/incrementable_traits.h>
 #include <__iterator/readable_traits.h>
 #include <concepts>
diff --git a/libcxx/include/__memory/compressed_pair.h b/libcxx/include/__memory/compressed_pair.h
--- a/libcxx/include/__memory/compressed_pair.h
+++ b/libcxx/include/__memory/compressed_pair.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___MEMORY_COMPRESSED_PAIR_H
 
 #include <__config>
+#include <__type_traits/dependent_type.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <tuple> // needed in c++03 for some constructors
diff --git a/libcxx/include/__ranges/join_view.h b/libcxx/include/__ranges/join_view.h
--- a/libcxx/include/__ranges/join_view.h
+++ b/libcxx/include/__ranges/join_view.h
@@ -25,6 +25,7 @@
 #include <__ranges/non_propagating_cache.h>
 #include <__ranges/range_adaptor.h>
 #include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
 #include <__utility/forward.h>
 #include <optional>
 #include <type_traits>
@@ -210,7 +211,7 @@
 
   public:
     using iterator_concept = _If<
-      __ref_is_glvalue && bidirectional_range<_Base> && bidirectional_range<range_reference_t<_Base>> && 
+      __ref_is_glvalue && bidirectional_range<_Base> && bidirectional_range<range_reference_t<_Base>> &&
           common_range<range_reference_t<_Base>>,
       bidirectional_iterator_tag,
       _If<
@@ -345,7 +346,7 @@
 
   template<class _Range>
   explicit join_view(_Range&&) -> join_view<views::all_t<_Range>>;
-  
+
 namespace views {
 namespace __join_view {
 struct __fn : __range_adaptor_closure<__fn> {
diff --git a/libcxx/include/__ranges/lazy_split_view.h b/libcxx/include/__ranges/lazy_split_view.h
--- a/libcxx/include/__ranges/lazy_split_view.h
+++ b/libcxx/include/__ranges/lazy_split_view.h
@@ -35,6 +35,7 @@
 #include <__ranges/single_view.h>
 #include <__ranges/subrange.h>
 #include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <type_traits>
diff --git a/libcxx/include/__ranges/take_view.h b/libcxx/include/__ranges/take_view.h
--- a/libcxx/include/__ranges/take_view.h
+++ b/libcxx/include/__ranges/take_view.h
@@ -30,6 +30,7 @@
 #include <__ranges/size.h>
 #include <__ranges/subrange.h>
 #include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
 #include <__utility/auto_cast.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/__ranges/transform_view.h b/libcxx/include/__ranges/transform_view.h
--- a/libcxx/include/__ranges/transform_view.h
+++ b/libcxx/include/__ranges/transform_view.h
@@ -30,6 +30,7 @@
 #include <__ranges/range_adaptor.h>
 #include <__ranges/size.h>
 #include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
 #include <__utility/forward.h>
 #include <__utility/in_place.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -600,6 +600,7 @@
 
 } // namespace this_thread
 
+template <class> struct _LIBCPP_TEMPLATE_VIS hash;
 template<> struct hash<__thread_id>;
 
 class _LIBCPP_TEMPLATE_VIS __thread_id
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -17,6 +17,7 @@
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
+#include <__type_traits/can_extract_key.h>
 #include <__utility/forward.h>
 #include <__utility/swap.h>
 #include <limits>
diff --git a/libcxx/include/__tuple b/libcxx/include/__tuple
--- a/libcxx/include/__tuple
+++ b/libcxx/include/__tuple
@@ -190,6 +190,9 @@
 
 // pair specializations
 
+template <class, class>
+struct _LIBCPP_TEMPLATE_VIS pair;
+
 template <class _T1, class _T2> struct __tuple_like<pair<_T1, _T2> > : true_type {};
 
 template <size_t _Ip, class _T1, class _T2>
diff --git a/libcxx/include/__type_traits/can_extract_key.h b/libcxx/include/__type_traits/can_extract_key.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__type_traits/can_extract_key.h
@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_CAN_EXTRACT_KEY_H
+#define _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H
+
+#include <__config>
+#include <__fwd/pair.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/remove_const.h>
+#include <__type_traits/remove_const_ref.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// These traits are used in __tree and __hash_table
+struct __extract_key_fail_tag {};
+struct __extract_key_self_tag {};
+struct __extract_key_first_tag {};
+
+template <class _ValTy, class _Key,
+          class _RawValTy = typename __unconstref<_ValTy>::type>
+struct __can_extract_key
+    : conditional<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag,
+                  __extract_key_fail_tag>::type {};
+
+template <class _Pair, class _Key, class _First, class _Second>
+struct __can_extract_key<_Pair, _Key, pair<_First, _Second> >
+    : conditional<_IsSame<typename remove_const<_First>::type, _Key>::value,
+                  __extract_key_first_tag, __extract_key_fail_tag>::type {};
+
+// __can_extract_map_key uses true_type/false_type instead of the tags.
+// It returns true if _Key != _ContainerValueTy (the container is a map not a set)
+// and _ValTy == _Key.
+template <class _ValTy, class _Key, class _ContainerValueTy,
+          class _RawValTy = typename __unconstref<_ValTy>::type>
+struct __can_extract_map_key
+    : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {};
+
+// This specialization returns __extract_key_fail_tag for non-map containers
+// because _Key == _ContainerValueTy
+template <class _ValTy, class _Key, class _RawValTy>
+struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
+    : false_type {};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__type_traits/dependent_type.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__type_traits/dependent_type.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__type_traits/dependent_type.h
@@ -1,37 +1,25 @@
-// -*- C++ -*-
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___TYPE_TRAITS_DEPENDENT_TYPE_H
+#define _LIBCPP___TYPE_TRAITS_DEPENDENT_TYPE_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template <class _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___TYPE_TRAITS_DEPENDENT_TYPE_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__type_traits/is_char_like_type.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__type_traits/is_char_like_type.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__type_traits/is_char_like_type.h
@@ -1,37 +1,28 @@
-// -*- C++ -*-
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___TYPE_TRAITS_IS_CHAR_LIKE_TYPE_H
+#define _LIBCPP___TYPE_TRAITS_IS_CHAR_LIKE_TYPE_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
+#include <__type_traits/conjunction.h>
+#include <__type_traits/is_standard_layout.h>
+#include <__type_traits/is_trivial.h>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template <class _CharT>
+using _IsCharLikeType = _And<is_standard_layout<_CharT>, is_trivial<_CharT> >;
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___TYPE_TRAITS_IS_CHAR_LIKE_TYPE_H
diff --git a/libcxx/include/__type_traits/is_implicitly_default_constructible.h b/libcxx/include/__type_traits/is_implicitly_default_constructible.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__type_traits/is_implicitly_default_constructible.h
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
+#define _LIBCPP___TYPE_TRAITS_IS_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
+
+#include <__config>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_default_constructible.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifndef _LIBCPP_CXX03_LANG
+// First of all, we can't implement this check in C++03 mode because the {}
+// default initialization syntax isn't valid.
+// Second, we implement the trait in a funny manner with two defaulted template
+// arguments to workaround Clang's PR43454.
+template <class _Tp>
+void __test_implicit_default_constructible(_Tp);
+
+template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type>
+struct __is_implicitly_default_constructible
+    : false_type
+{ };
+
+template <class _Tp>
+struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), true_type>
+    : true_type
+{ };
+
+template <class _Tp>
+struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), false_type>
+    : false_type
+{ };
+#endif // !C++03
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
diff --git a/libcxx/include/__type_traits/is_swappable.h b/libcxx/include/__type_traits/is_swappable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__type_traits/is_swappable.h
@@ -0,0 +1,165 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_SWAPPABLE_H
+#define _LIBCPP___TYPE_TRAITS_IS_SWAPPABLE_H
+
+#include <__config>
+#include <__type_traits/add_lvalue_reference.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/enable_if.h>
+#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_referenceable.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/is_swappable.h>
+#include <__type_traits/is_void.h>
+#include <__type_traits/nat.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp> struct __is_swappable;
+template <class _Tp> struct __is_nothrow_swappable;
+
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Tp>
+using __swap_result_t = typename enable_if<is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value>::type;
+#else
+template <class>
+using __swap_result_t = void;
+#endif
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_CONSTEXPR_AFTER_CXX17 __swap_result_t<_Tp>
+swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
+                                    is_nothrow_move_assignable<_Tp>::value);
+
+template<class _Tp, size_t _Np>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+typename enable_if<
+    __is_swappable<_Tp>::value
+>::type
+swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value);
+
+namespace __detail
+{
+// ALL generic swap overloads MUST already have a declaration available at this point.
+
+template <class _Tp, class _Up = _Tp,
+          bool _NotVoid = !is_void<_Tp>::value && !is_void<_Up>::value>
+struct __swappable_with
+{
+    template <class _LHS, class _RHS>
+    static decltype(swap(declval<_LHS>(), declval<_RHS>()))
+    __test_swap(int);
+    template <class, class>
+    static __nat __test_swap(long);
+
+    // Extra parens are needed for the C++03 definition of decltype.
+    typedef decltype((__test_swap<_Tp, _Up>(0))) __swap1;
+    typedef decltype((__test_swap<_Up, _Tp>(0))) __swap2;
+
+    static const bool value = _IsNotSame<__swap1, __nat>::value
+                           && _IsNotSame<__swap2, __nat>::value;
+};
+
+template <class _Tp, class _Up>
+struct __swappable_with<_Tp, _Up,  false> : false_type {};
+
+template <class _Tp, class _Up = _Tp, bool _Swappable = __swappable_with<_Tp, _Up>::value>
+struct __nothrow_swappable_with {
+  static const bool value =
+#ifndef _LIBCPP_HAS_NO_NOEXCEPT
+      noexcept(swap(declval<_Tp>(), declval<_Up>()))
+  &&  noexcept(swap(declval<_Up>(), declval<_Tp>()));
+#else
+      false;
+#endif
+};
+
+template <class _Tp, class _Up>
+struct __nothrow_swappable_with<_Tp, _Up, false> : false_type {};
+
+} // namespace __detail
+
+template <class _Tp>
+struct __is_swappable
+    : public integral_constant<bool, __detail::__swappable_with<_Tp&>::value>
+{
+};
+
+template <class _Tp>
+struct __is_nothrow_swappable
+    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp&>::value>
+{
+};
+
+#if _LIBCPP_STD_VER > 14
+
+template <class _Tp, class _Up>
+struct _LIBCPP_TEMPLATE_VIS is_swappable_with
+    : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value>
+{
+};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_swappable
+    : public conditional<
+        __is_referenceable<_Tp>::value,
+        is_swappable_with<
+            typename add_lvalue_reference<_Tp>::type,
+            typename add_lvalue_reference<_Tp>::type>,
+        false_type
+    >::type
+{
+};
+
+template <class _Tp, class _Up>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with
+    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value>
+{
+};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable
+    : public conditional<
+        __is_referenceable<_Tp>::value,
+        is_nothrow_swappable_with<
+            typename add_lvalue_reference<_Tp>::type,
+            typename add_lvalue_reference<_Tp>::type>,
+        false_type
+    >::type
+{
+};
+
+template <class _Tp, class _Up>
+inline constexpr bool is_swappable_with_v = is_swappable_with<_Tp, _Up>::value;
+
+template <class _Tp>
+inline constexpr bool is_swappable_v = is_swappable<_Tp>::value;
+
+template <class _Tp, class _Up>
+inline constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<_Tp, _Up>::value;
+
+template <class _Tp>
+inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<_Tp>::value;
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_SWAPPABLE_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__type_traits/make_const_lvalue_ref.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__type_traits/make_const_lvalue_ref.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__type_traits/make_const_lvalue_ref.h
@@ -1,37 +1,26 @@
-// -*- C++ -*-
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___TYPE_TRAITS_MAKE_CONST_LVALUE_REF_H
+#define _LIBCPP___TYPE_TRAITS_MAKE_CONST_LVALUE_REF_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
+#include <__type_traits/remove_reference.h>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template<class _Tp>
+using __make_const_lvalue_ref = const typename remove_reference<_Tp>::type&;
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___TYPE_TRAITS_MAKE_CONST_LVALUE_REF_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__type_traits/maybe_const.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__type_traits/maybe_const.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__type_traits/maybe_const.h
@@ -1,37 +1,26 @@
-// -*- C++ -*-
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___TYPE_TRAITS_MAYBE_CONST_H
+#define _LIBCPP___TYPE_TRAITS_MAYBE_CONST_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
+#include <__type_traits/conditional.h>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template<bool _Const, class _Tp>
+using __maybe_const = typename conditional<_Const, const _Tp, _Tp>::type;
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___TYPE_TRAITS_MAYBE_CONST_H
diff --git a/libcxx/include/__fwd/span.h b/libcxx/include/__type_traits/remove_const_ref.h
copy from libcxx/include/__fwd/span.h
copy to libcxx/include/__type_traits/remove_const_ref.h
--- a/libcxx/include/__fwd/span.h
+++ b/libcxx/include/__type_traits/remove_const_ref.h
@@ -1,37 +1,29 @@
-// -*- C++ -*-
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-//===---------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FWD_SPAN_H
-#define _LIBCPP_FWD_SPAN_H
+#ifndef _LIBCPP___TYPE_TRAITS_REMOVE_CONST_REF_H
+#define _LIBCPP___TYPE_TRAITS_REMOVE_CONST_REF_H
 
 #include <__config>
-#include <cstddef>
-#include <limits>
+#include <__type_traits/remove_const.h>
+#include <__type_traits/remove_reference.h>
 
 #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
-
-inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
-template <typename _Tp, size_t _Extent = dynamic_extent> class span;
-
-#endif
+template <class _Tp>
+struct __unconstref {
+    typedef _LIBCPP_NODEBUG typename remove_const<typename remove_reference<_Tp>::type>::type type;
+};
 
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP_FWD_SPAN_H
+#endif // _LIBCPP___TYPE_TRAITS_REMOVE_CONST_REF_H
diff --git a/libcxx/include/__type_traits/result_of.h b/libcxx/include/__type_traits/result_of.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__type_traits/result_of.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___TYPE_TRAITS_RESULT_OF_H
+#define _LIBCPP___TYPE_TRAITS_RESULT_OF_H
+
+#include <__config>
+#include <__functional/invoke.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// result_of
+
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
+template <class _Callable> class _LIBCPP_DEPRECATED_IN_CXX17 result_of;
+
+template <class _Fp, class ..._Args>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)>
+    : public __invoke_of<_Fp, _Args...>
+{
+};
+
+#if _LIBCPP_STD_VER > 11
+template <class _Tp> using result_of_t _LIBCPP_DEPRECATED_IN_CXX17 = typename result_of<_Tp>::type;
+#endif // _LIBCPP_STD_VER > 11
+#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_RESULT_OF_H
diff --git a/libcxx/include/__utility/convert_to_integral.h b/libcxx/include/__utility/convert_to_integral.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__utility/convert_to_integral.h
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_CONVERT_TO_INTEGRAL_H
+#define _LIBCPP___UTILITY_CONVERT_TO_INTEGRAL_H
+
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_enum.h>
+#include <__type_traits/is_floating_point.h>
+#include <__type_traits/underlying_type.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+int __convert_to_integral(int __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+unsigned __convert_to_integral(unsigned __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+long __convert_to_integral(long __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+unsigned long __convert_to_integral(unsigned long __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+long long __convert_to_integral(long long __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+unsigned long long __convert_to_integral(unsigned long long __val) {return __val; }
+
+template<typename _Fp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+typename enable_if<is_floating_point<_Fp>::value, long long>::type
+ __convert_to_integral(_Fp __val) { return __val; }
+
+#ifndef _LIBCPP_HAS_NO_INT128
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+__int128_t __convert_to_integral(__int128_t __val) { return __val; }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+__uint128_t __convert_to_integral(__uint128_t __val) { return __val; }
+#endif
+
+template <class _Tp, bool = is_enum<_Tp>::value>
+struct __sfinae_underlying_type
+{
+    typedef typename underlying_type<_Tp>::type type;
+    typedef decltype(((type)1) + 0) __promoted_type;
+};
+
+template <class _Tp>
+struct __sfinae_underlying_type<_Tp, false> {};
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+typename __sfinae_underlying_type<_Tp>::__promoted_type
+__convert_to_integral(_Tp __val) { return __val; }
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_CONVERT_TO_INTEGRAL_H
diff --git a/libcxx/include/__utility/pair.h b/libcxx/include/__utility/pair.h
--- a/libcxx/include/__utility/pair.h
+++ b/libcxx/include/__utility/pair.h
@@ -14,6 +14,7 @@
 #include <__config>
 #include <__functional/unwrap_ref.h>
 #include <__tuple>
+#include <__type_traits/is_implicitly_default_constructible.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/piecewise_construct.h>
diff --git a/libcxx/include/bitset b/libcxx/include/bitset
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -118,6 +118,7 @@
 #include <__config>
 #include <__functional/hash.h>
 #include <__functional/unary_function.h>
+#include <__type_traits/is_char_like_type.h>
 #include <climits>
 #include <cstddef>
 #include <stdexcept>
diff --git a/libcxx/include/experimental/propagate_const b/libcxx/include/experimental/propagate_const
--- a/libcxx/include/experimental/propagate_const
+++ b/libcxx/include/experimental/propagate_const
@@ -108,6 +108,7 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__functional/hash.h>
 #include <__functional/operations.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -280,7 +280,10 @@
       module is_sorted                       { private header "__algorithm/is_sorted.h" }
       module is_sorted_until                 { private header "__algorithm/is_sorted_until.h" }
       module iter_swap                       { private header "__algorithm/iter_swap.h" }
-      module iterator_operations             { private header "__algorithm/iterator_operations.h" }
+      module iterator_operations             {
+        private header "__algorithm/iterator_operations.h"
+        export *
+      }
       module lexicographical_compare         { private header "__algorithm/lexicographical_compare.h" }
       module lower_bound                     { private header "__algorithm/lower_bound.h" }
       module make_heap                       { private header "__algorithm/make_heap.h" }
@@ -1084,122 +1087,131 @@
     export functional.__functional.unwrap_ref
     export *
 
-    module add_const                          { private header "__type_traits/add_const.h" }
-    module add_cv                             { private header "__type_traits/add_cv.h" }
-    module add_lvalue_reference               { private header "__type_traits/add_lvalue_reference.h" }
-    module add_pointer                        { private header "__type_traits/add_pointer.h" }
-    module add_rvalue_reference               { private header "__type_traits/add_rvalue_reference.h" }
-    module add_volatile                       { private header "__type_traits/add_volatile.h" }
-    module aligned_storage                    { private header "__type_traits/aligned_storage.h" }
-    module aligned_union                      { private header "__type_traits/aligned_union.h" }
-    module alignment_of                       { private header "__type_traits/alignment_of.h" }
-    module apply_cv                           { private header "__type_traits/apply_cv.h" }
-    module common_reference                   { private header "__type_traits/common_reference.h" }
-    module common_type                        { private header "__type_traits/common_type.h" }
-    module conditional                        { private header "__type_traits/conditional.h" }
-    module conjunction                        { private header "__type_traits/conjunction.h" }
-    module copy_cv                            { private header "__type_traits/copy_cv.h" }
-    module copy_cvref                         { private header "__type_traits/copy_cvref.h" }
-    module decay                              { private header "__type_traits/decay.h" }
-    module disjunction                        { private header "__type_traits/disjunction.h" }
-    module enable_if                          { private header "__type_traits/enable_if.h" }
-    module extent                             { private header "__type_traits/extent.h" }
-    module has_unique_object_representation   { private header "__type_traits/has_unique_object_representation.h" }
-    module has_virtual_destructor             { private header "__type_traits/has_virtual_destructor.h" }
-    module integral_constant                  { private header "__type_traits/integral_constant.h" }
-    module is_abstract                        { private header "__type_traits/is_abstract.h" }
-    module is_aggregate                       { private header "__type_traits/is_aggregate.h" }
-    module is_arithmetic                      { private header "__type_traits/is_arithmetic.h" }
-    module is_array                           { private header "__type_traits/is_array.h" }
-    module is_assignable                      { private header "__type_traits/is_assignable.h" }
-    module is_base_of                         { private header "__type_traits/is_base_of.h" }
-    module is_bounded_array                   { private header "__type_traits/is_bounded_array.h" }
-    module is_callable                        { private header "__type_traits/is_callable.h" }
-    module is_class                           { private header "__type_traits/is_class.h" }
-    module is_compound                        { private header "__type_traits/is_compound.h" }
-    module is_const                           { private header "__type_traits/is_const.h" }
-    module is_constant_evaluated              { private header "__type_traits/is_constant_evaluated.h" }
-    module is_constructible                   { private header "__type_traits/is_constructible.h" }
-    module is_convertible                     { private header "__type_traits/is_convertible.h" }
-    module is_copy_assignable                 { private header "__type_traits/is_copy_assignable.h" }
-    module is_copy_constructible              { private header "__type_traits/is_copy_constructible.h" }
-    module is_core_convertible                { private header "__type_traits/is_core_convertible.h" }
-    module is_default_constructible           { private header "__type_traits/is_default_constructible.h" }
-    module is_destructible                    { private header "__type_traits/is_destructible.h" }
-    module is_empty                           { private header "__type_traits/is_empty.h" }
-    module is_enum                            { private header "__type_traits/is_enum.h" }
-    module is_final                           { private header "__type_traits/is_final.h" }
-    module is_floating_point                  { private header "__type_traits/is_floating_point.h" }
-    module is_function                        { private header "__type_traits/is_function.h" }
-    module is_fundamental                     { private header "__type_traits/is_fundamental.h" }
-    module is_integral                        { private header "__type_traits/is_integral.h" }
-    module is_literal_type                    { private header "__type_traits/is_literal_type.h" }
-    module is_member_function_pointer         { private header "__type_traits/is_member_function_pointer.h" }
-    module is_member_object_pointer           { private header "__type_traits/is_member_object_pointer.h" }
-    module is_member_pointer                  { private header "__type_traits/is_member_pointer.h" }
-    module is_move_assignable                 { private header "__type_traits/is_move_assignable.h" }
-    module is_move_constructible              { private header "__type_traits/is_move_constructible.h" }
-    module is_nothrow_assignable              { private header "__type_traits/is_nothrow_assignable.h" }
-    module is_nothrow_constructible           { private header "__type_traits/is_nothrow_constructible.h" }
-    module is_nothrow_convertible             { private header "__type_traits/is_nothrow_convertible.h" }
-    module is_nothrow_copy_assignable         { private header "__type_traits/is_nothrow_copy_assignable.h" }
-    module is_nothrow_copy_constructible      { private header "__type_traits/is_nothrow_copy_constructible.h" }
-    module is_nothrow_default_constructible   { private header "__type_traits/is_nothrow_default_constructible.h" }
-    module is_nothrow_destructible            { private header "__type_traits/is_nothrow_destructible.h" }
-    module is_nothrow_move_assignable         { private header "__type_traits/is_nothrow_move_assignable.h" }
-    module is_nothrow_move_constructible      { private header "__type_traits/is_nothrow_move_constructible.h" }
-    module is_null_pointer                    { private header "__type_traits/is_null_pointer.h" }
-    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_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_standard_layout                 { private header "__type_traits/is_standard_layout.h" }
-    module is_trivial                         { private header "__type_traits/is_trivial.h" }
-    module is_trivially_assignable            { private header "__type_traits/is_trivially_assignable.h" }
-    module is_trivially_constructible         { private header "__type_traits/is_trivially_constructible.h" }
-    module is_trivially_copy_assignable       { private header "__type_traits/is_trivially_copy_assignable.h" }
-    module is_trivially_copy_constructible    { private header "__type_traits/is_trivially_copy_constructible.h" }
-    module is_trivially_copyable              { private header "__type_traits/is_trivially_copyable.h" }
-    module is_trivially_default_constructible { private header "__type_traits/is_trivially_default_constructible.h" }
-    module is_trivially_destructible          { private header "__type_traits/is_trivially_destructible.h" }
-    module is_trivially_move_assignable       { private header "__type_traits/is_trivially_move_assignable.h" }
-    module is_trivially_move_constructible    { private header "__type_traits/is_trivially_move_constructible.h" }
-    module is_unbounded_array                 { private header "__type_traits/is_unbounded_array.h" }
-    module is_union                           { private header "__type_traits/is_union.h" }
-    module is_unsigned                        { private header "__type_traits/is_unsigned.h" }
-    module is_unsigned_integer                { private header "__type_traits/is_unsigned_integer.h" }
-    module is_valid_expansion                 { private header "__type_traits/is_valid_expansion.h" }
-    module is_void                            { private header "__type_traits/is_void.h" }
-    module is_volatile                        { private header "__type_traits/is_volatile.h" }
-    module lazy                               { private header "__type_traits/lazy.h" }
-    module make_32_64_or_128_bit              { private header "__type_traits/make_32_64_or_128_bit.h" }
-    module make_signed                        { private header "__type_traits/make_signed.h" }
-    module make_unsigned                      { private header "__type_traits/make_unsigned.h" }
-    module nat                                { private header "__type_traits/nat.h" }
-    module negation                           { private header "__type_traits/negation.h" }
-    module promote                            { private header "__type_traits/promote.h" }
-    module rank                               { private header "__type_traits/rank.h" }
-    module remove_all_extents                 { private header "__type_traits/remove_all_extents.h" }
-    module remove_const                       { private header "__type_traits/remove_const.h" }
-    module remove_cv                          { private header "__type_traits/remove_cv.h" }
-    module remove_cvref                       { private header "__type_traits/remove_cvref.h" }
-    module remove_extent                      { private header "__type_traits/remove_extent.h" }
-    module remove_pointer                     { private header "__type_traits/remove_pointer.h" }
-    module remove_reference                   { private header "__type_traits/remove_reference.h" }
-    module remove_volatile                    { private header "__type_traits/remove_volatile.h" }
-    module type_identity                      { private header "__type_traits/type_identity.h" }
-    module type_list                          { private header "__type_traits/type_list.h" }
-    module underlying_type                    { private header "__type_traits/underlying_type.h" }
-    module void_t                             { private header "__type_traits/void_t.h" }
+    module add_const                           { private header "__type_traits/add_const.h" }
+    module add_cv                              { private header "__type_traits/add_cv.h" }
+    module add_lvalue_reference                { private header "__type_traits/add_lvalue_reference.h" }
+    module add_pointer                         { private header "__type_traits/add_pointer.h" }
+    module add_rvalue_reference                { private header "__type_traits/add_rvalue_reference.h" }
+    module add_volatile                        { private header "__type_traits/add_volatile.h" }
+    module aligned_storage                     { private header "__type_traits/aligned_storage.h" }
+    module aligned_union                       { private header "__type_traits/aligned_union.h" }
+    module alignment_of                        { private header "__type_traits/alignment_of.h" }
+    module apply_cv                            { private header "__type_traits/apply_cv.h" }
+    module can_extract_key                     { private header "__type_traits/can_extract_key.h" }
+    module common_reference                    { private header "__type_traits/common_reference.h" }
+    module common_type                         { private header "__type_traits/common_type.h" }
+    module conditional                         { private header "__type_traits/conditional.h" }
+    module conjunction                         { private header "__type_traits/conjunction.h" }
+    module copy_cv                             { private header "__type_traits/copy_cv.h" }
+    module copy_cvref                          { private header "__type_traits/copy_cvref.h" }
+    module decay                               { private header "__type_traits/decay.h" }
+    module dependent_type                      { private header "__type_traits/dependent_type.h" }
+    module disjunction                         { private header "__type_traits/disjunction.h" }
+    module enable_if                           { private header "__type_traits/enable_if.h" }
+    module extent                              { private header "__type_traits/extent.h" }
+    module has_unique_object_representation    { private header "__type_traits/has_unique_object_representation.h" }
+    module has_virtual_destructor              { private header "__type_traits/has_virtual_destructor.h" }
+    module integral_constant                   { private header "__type_traits/integral_constant.h" }
+    module is_abstract                         { private header "__type_traits/is_abstract.h" }
+    module is_aggregate                        { private header "__type_traits/is_aggregate.h" }
+    module is_arithmetic                       { private header "__type_traits/is_arithmetic.h" }
+    module is_array                            { private header "__type_traits/is_array.h" }
+    module is_assignable                       { private header "__type_traits/is_assignable.h" }
+    module is_base_of                          { private header "__type_traits/is_base_of.h" }
+    module is_bounded_array                    { private header "__type_traits/is_bounded_array.h" }
+    module is_callable                         { private header "__type_traits/is_callable.h" }
+    module is_char_like_type                   { private header "__type_traits/is_char_like_type.h" }
+    module is_class                            { private header "__type_traits/is_class.h" }
+    module is_compound                         { private header "__type_traits/is_compound.h" }
+    module is_const                            { private header "__type_traits/is_const.h" }
+    module is_constant_evaluated               { private header "__type_traits/is_constant_evaluated.h" }
+    module is_constructible                    { private header "__type_traits/is_constructible.h" }
+    module is_convertible                      { private header "__type_traits/is_convertible.h" }
+    module is_copy_assignable                  { private header "__type_traits/is_copy_assignable.h" }
+    module is_copy_constructible               { private header "__type_traits/is_copy_constructible.h" }
+    module is_core_convertible                 { private header "__type_traits/is_core_convertible.h" }
+    module is_default_constructible            { private header "__type_traits/is_default_constructible.h" }
+    module is_destructible                     { private header "__type_traits/is_destructible.h" }
+    module is_empty                            { private header "__type_traits/is_empty.h" }
+    module is_enum                             { private header "__type_traits/is_enum.h" }
+    module is_final                            { private header "__type_traits/is_final.h" }
+    module is_floating_point                   { private header "__type_traits/is_floating_point.h" }
+    module is_function                         { private header "__type_traits/is_function.h" }
+    module is_fundamental                      { private header "__type_traits/is_fundamental.h" }
+    module is_implicitly_default_constructible { private header "__type_traits/is_implicitly_default_constructible.h" }
+    module is_integral                         { private header "__type_traits/is_integral.h" }
+    module is_literal_type                     { private header "__type_traits/is_literal_type.h" }
+    module is_member_function_pointer          { private header "__type_traits/is_member_function_pointer.h" }
+    module is_member_object_pointer            { private header "__type_traits/is_member_object_pointer.h" }
+    module is_member_pointer                   { private header "__type_traits/is_member_pointer.h" }
+    module is_move_assignable                  { private header "__type_traits/is_move_assignable.h" }
+    module is_move_constructible               { private header "__type_traits/is_move_constructible.h" }
+    module is_nothrow_assignable               { private header "__type_traits/is_nothrow_assignable.h" }
+    module is_nothrow_constructible            { private header "__type_traits/is_nothrow_constructible.h" }
+    module is_nothrow_convertible              { private header "__type_traits/is_nothrow_convertible.h" }
+    module is_nothrow_copy_assignable          { private header "__type_traits/is_nothrow_copy_assignable.h" }
+    module is_nothrow_copy_constructible       { private header "__type_traits/is_nothrow_copy_constructible.h" }
+    module is_nothrow_default_constructible    { private header "__type_traits/is_nothrow_default_constructible.h" }
+    module is_nothrow_destructible             { private header "__type_traits/is_nothrow_destructible.h" }
+    module is_nothrow_move_assignable          { private header "__type_traits/is_nothrow_move_assignable.h" }
+    module is_nothrow_move_constructible       { private header "__type_traits/is_nothrow_move_constructible.h" }
+    module is_null_pointer                     { private header "__type_traits/is_null_pointer.h" }
+    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_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_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" }
+    module is_trivially_assignable             { private header "__type_traits/is_trivially_assignable.h" }
+    module is_trivially_constructible          { private header "__type_traits/is_trivially_constructible.h" }
+    module is_trivially_copy_assignable        { private header "__type_traits/is_trivially_copy_assignable.h" }
+    module is_trivially_copy_constructible     { private header "__type_traits/is_trivially_copy_constructible.h" }
+    module is_trivially_copyable               { private header "__type_traits/is_trivially_copyable.h" }
+    module is_trivially_default_constructible  { private header "__type_traits/is_trivially_default_constructible.h" }
+    module is_trivially_destructible           { private header "__type_traits/is_trivially_destructible.h" }
+    module is_trivially_move_assignable        { private header "__type_traits/is_trivially_move_assignable.h" }
+    module is_trivially_move_constructible     { private header "__type_traits/is_trivially_move_constructible.h" }
+    module is_unbounded_array                  { private header "__type_traits/is_unbounded_array.h" }
+    module is_union                            { private header "__type_traits/is_union.h" }
+    module is_unsigned                         { private header "__type_traits/is_unsigned.h" }
+    module is_unsigned_integer                 { private header "__type_traits/is_unsigned_integer.h" }
+    module is_valid_expansion                  { private header "__type_traits/is_valid_expansion.h" }
+    module is_void                             { private header "__type_traits/is_void.h" }
+    module is_volatile                         { private header "__type_traits/is_volatile.h" }
+    module lazy                                { private header "__type_traits/lazy.h" }
+    module make_32_64_or_128_bit               { private header "__type_traits/make_32_64_or_128_bit.h" }
+    module make_const_lvalue_ref               { private header "__type_traits/make_const_lvalue_ref.h" }
+    module make_signed                         { private header "__type_traits/make_signed.h" }
+    module make_unsigned                       { private header "__type_traits/make_unsigned.h" }
+    module maybe_const                         { private header "__type_traits/maybe_const.h" }
+    module nat                                 { private header "__type_traits/nat.h" }
+    module negation                            { private header "__type_traits/negation.h" }
+    module promote                             { private header "__type_traits/promote.h" }
+    module rank                                { private header "__type_traits/rank.h" }
+    module remove_all_extents                  { private header "__type_traits/remove_all_extents.h" }
+    module remove_const                        { private header "__type_traits/remove_const.h" }
+    module remove_const_ref                    { private header "__type_traits/remove_const_ref.h" }
+    module remove_cv                           { private header "__type_traits/remove_cv.h" }
+    module remove_cvref                        { private header "__type_traits/remove_cvref.h" }
+    module remove_extent                       { private header "__type_traits/remove_extent.h" }
+    module remove_pointer                      { private header "__type_traits/remove_pointer.h" }
+    module remove_reference                    { private header "__type_traits/remove_reference.h" }
+    module remove_volatile                     { private header "__type_traits/remove_volatile.h" }
+    module result_of                           { private header "__type_traits/result_of.h" }
+    module type_identity                       { private header "__type_traits/type_identity.h" }
+    module type_list                           { private header "__type_traits/type_list.h" }
+    module underlying_type                     { private header "__type_traits/underlying_type.h" }
+    module void_t                              { private header "__type_traits/void_t.h" }
   }
   module typeindex {
     header "typeindex"
@@ -1228,6 +1240,7 @@
       module as_const            { private header "__utility/as_const.h" }
       module auto_cast           { private header "__utility/auto_cast.h" }
       module cmp                 { private header "__utility/cmp.h" }
+      module convert_to_integral { private header "__utility/convert_to_integral.h" }
       module declval             { private header "__utility/declval.h" }
       module exchange            { private header "__utility/exchange.h" }
       module forward             { private header "__utility/forward.h" }
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -209,6 +209,7 @@
 #include <__memory/allocator_arg_t.h>
 #include <__memory/uses_allocator.h>
 #include <__tuple>
+#include <__type_traits/maybe_const.h>
 #include <__utility/forward.h>
 #include <__utility/integer_sequence.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -419,6 +419,7 @@
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__functional/invoke.h>
+#include <__fwd/hash.h>
 #include <__type_traits/add_const.h>
 #include <__type_traits/add_cv.h>
 #include <__type_traits/add_lvalue_reference.h>
@@ -493,6 +494,7 @@
 #include <__type_traits/is_scoped_enum.h>
 #include <__type_traits/is_signed.h>
 #include <__type_traits/is_standard_layout.h>
+#include <__type_traits/is_swappable.h>
 #include <__type_traits/is_trivial.h>
 #include <__type_traits/is_trivially_assignable.h>
 #include <__type_traits/is_trivially_constructible.h>
@@ -519,6 +521,7 @@
 #include <__type_traits/remove_pointer.h>
 #include <__type_traits/remove_reference.h>
 #include <__type_traits/remove_volatile.h>
+#include <__type_traits/result_of.h>
 #include <__type_traits/type_identity.h>
 #include <__type_traits/underlying_type.h>
 #include <__type_traits/void_t.h>
@@ -531,280 +534,4 @@
 #  pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS pair;
-template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
-
-// Member detector base
-
-template <class _Tp, bool>
-struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
-
-// is_integral
-
-template <class _Tp>
-struct __unconstref {
-    typedef _LIBCPP_NODEBUG typename remove_const<typename remove_reference<_Tp>::type>::type type;
-};
-
-#ifndef _LIBCPP_CXX03_LANG
-// First of all, we can't implement this check in C++03 mode because the {}
-// default initialization syntax isn't valid.
-// Second, we implement the trait in a funny manner with two defaulted template
-// arguments to workaround Clang's PR43454.
-template <class _Tp>
-void __test_implicit_default_constructible(_Tp);
-
-template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type>
-struct __is_implicitly_default_constructible
-    : false_type
-{ };
-
-template <class _Tp>
-struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), true_type>
-    : true_type
-{ };
-
-template <class _Tp>
-struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), false_type>
-    : false_type
-{ };
-#endif // !C++03
-
-// result_of
-
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
-template <class _Callable> class _LIBCPP_DEPRECATED_IN_CXX17 result_of;
-
-template <class _Fp, class ..._Args>
-class _LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)>
-    : public __invoke_of<_Fp, _Args...>
-{
-};
-
-#if _LIBCPP_STD_VER > 11
-template <class _Tp> using result_of_t _LIBCPP_DEPRECATED_IN_CXX17 = typename result_of<_Tp>::type;
-#endif // _LIBCPP_STD_VER > 11
-#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
-
-// __swappable
-
-template <class _Tp> struct __is_swappable;
-template <class _Tp> struct __is_nothrow_swappable;
-
-
-#ifndef _LIBCPP_CXX03_LANG
-template <class _Tp>
-using __swap_result_t = typename enable_if<is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value>::type;
-#else
-template <class>
-using __swap_result_t = void;
-#endif
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
-_LIBCPP_CONSTEXPR_AFTER_CXX17 __swap_result_t<_Tp>
-swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
-                                    is_nothrow_move_assignable<_Tp>::value);
-
-template<class _Tp, size_t _Np>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-typename enable_if<
-    __is_swappable<_Tp>::value
->::type
-swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value);
-
-namespace __detail
-{
-// ALL generic swap overloads MUST already have a declaration available at this point.
-
-template <class _Tp, class _Up = _Tp,
-          bool _NotVoid = !is_void<_Tp>::value && !is_void<_Up>::value>
-struct __swappable_with
-{
-    template <class _LHS, class _RHS>
-    static decltype(swap(declval<_LHS>(), declval<_RHS>()))
-    __test_swap(int);
-    template <class, class>
-    static __nat __test_swap(long);
-
-    // Extra parens are needed for the C++03 definition of decltype.
-    typedef decltype((__test_swap<_Tp, _Up>(0))) __swap1;
-    typedef decltype((__test_swap<_Up, _Tp>(0))) __swap2;
-
-    static const bool value = _IsNotSame<__swap1, __nat>::value
-                           && _IsNotSame<__swap2, __nat>::value;
-};
-
-template <class _Tp, class _Up>
-struct __swappable_with<_Tp, _Up,  false> : false_type {};
-
-template <class _Tp, class _Up = _Tp, bool _Swappable = __swappable_with<_Tp, _Up>::value>
-struct __nothrow_swappable_with {
-  static const bool value =
-#ifndef _LIBCPP_HAS_NO_NOEXCEPT
-      noexcept(swap(declval<_Tp>(), declval<_Up>()))
-  &&  noexcept(swap(declval<_Up>(), declval<_Tp>()));
-#else
-      false;
-#endif
-};
-
-template <class _Tp, class _Up>
-struct __nothrow_swappable_with<_Tp, _Up, false> : false_type {};
-
-} // namespace __detail
-
-template <class _Tp>
-struct __is_swappable
-    : public integral_constant<bool, __detail::__swappable_with<_Tp&>::value>
-{
-};
-
-template <class _Tp>
-struct __is_nothrow_swappable
-    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp&>::value>
-{
-};
-
-#if _LIBCPP_STD_VER > 14
-
-template <class _Tp, class _Up>
-struct _LIBCPP_TEMPLATE_VIS is_swappable_with
-    : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value>
-{
-};
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS is_swappable
-    : public conditional<
-        __is_referenceable<_Tp>::value,
-        is_swappable_with<
-            typename add_lvalue_reference<_Tp>::type,
-            typename add_lvalue_reference<_Tp>::type>,
-        false_type
-    >::type
-{
-};
-
-template <class _Tp, class _Up>
-struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with
-    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value>
-{
-};
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable
-    : public conditional<
-        __is_referenceable<_Tp>::value,
-        is_nothrow_swappable_with<
-            typename add_lvalue_reference<_Tp>::type,
-            typename add_lvalue_reference<_Tp>::type>,
-        false_type
-    >::type
-{
-};
-
-template <class _Tp, class _Up>
-inline constexpr bool is_swappable_with_v = is_swappable_with<_Tp, _Up>::value;
-
-template <class _Tp>
-inline constexpr bool is_swappable_v = is_swappable<_Tp>::value;
-
-template <class _Tp, class _Up>
-inline constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<_Tp, _Up>::value;
-
-template <class _Tp>
-inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<_Tp>::value;
-
-#endif // _LIBCPP_STD_VER > 14
-
-template <class _Tp, bool = is_enum<_Tp>::value>
-struct __sfinae_underlying_type
-{
-    typedef typename underlying_type<_Tp>::type type;
-    typedef decltype(((type)1) + 0) __promoted_type;
-};
-
-template <class _Tp>
-struct __sfinae_underlying_type<_Tp, false> {};
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-int __convert_to_integral(int __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-unsigned __convert_to_integral(unsigned __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-long __convert_to_integral(long __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-unsigned long __convert_to_integral(unsigned long __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-long long __convert_to_integral(long long __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-unsigned long long __convert_to_integral(unsigned long long __val) {return __val; }
-
-template<typename _Fp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-typename enable_if<is_floating_point<_Fp>::value, long long>::type
- __convert_to_integral(_Fp __val) { return __val; }
-
-#ifndef _LIBCPP_HAS_NO_INT128
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-__int128_t __convert_to_integral(__int128_t __val) { return __val; }
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-__uint128_t __convert_to_integral(__uint128_t __val) { return __val; }
-#endif
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-typename __sfinae_underlying_type<_Tp>::__promoted_type
-__convert_to_integral(_Tp __val) { return __val; }
-
-// These traits are used in __tree and __hash_table
-struct __extract_key_fail_tag {};
-struct __extract_key_self_tag {};
-struct __extract_key_first_tag {};
-
-template <class _ValTy, class _Key,
-          class _RawValTy = typename __unconstref<_ValTy>::type>
-struct __can_extract_key
-    : conditional<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag,
-                  __extract_key_fail_tag>::type {};
-
-template <class _Pair, class _Key, class _First, class _Second>
-struct __can_extract_key<_Pair, _Key, pair<_First, _Second> >
-    : conditional<_IsSame<typename remove_const<_First>::type, _Key>::value,
-                  __extract_key_first_tag, __extract_key_fail_tag>::type {};
-
-// __can_extract_map_key uses true_type/false_type instead of the tags.
-// It returns true if _Key != _ContainerValueTy (the container is a map not a set)
-// and _ValTy == _Key.
-template <class _ValTy, class _Key, class _ContainerValueTy,
-          class _RawValTy = typename __unconstref<_ValTy>::type>
-struct __can_extract_map_key
-    : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {};
-
-// This specialization returns __extract_key_fail_tag for non-map containers
-// because _Key == _ContainerValueTy
-template <class _ValTy, class _Key, class _RawValTy>
-struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
-    : false_type {};
-
-template <class _CharT>
-using _IsCharLikeType = _And<is_standard_layout<_CharT>, is_trivial<_CharT> >;
-
-template<class _Tp>
-using __make_const_lvalue_ref = const typename remove_reference<_Tp>::type&;
-
-template<bool _Const, class _Tp>
-using __maybe_const = typename conditional<_Const, const _Tp, _Tp>::type;
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif // _LIBCPP_TYPE_TRAITS
diff --git a/libcxx/include/variant b/libcxx/include/variant
--- a/libcxx/include/variant
+++ b/libcxx/include/variant
@@ -206,6 +206,7 @@
 #include <__functional/operations.h>
 #include <__functional/unary_function.h>
 #include <__tuple>
+#include <__type_traits/dependent_type.h>
 #include <__utility/forward.h>
 #include <__utility/in_place.h>
 #include <__utility/move.h>
diff --git a/libcxx/test/libcxx/private_headers.verify.cpp b/libcxx/test/libcxx/private_headers.verify.cpp
--- a/libcxx/test/libcxx/private_headers.verify.cpp
+++ b/libcxx/test/libcxx/private_headers.verify.cpp
@@ -521,6 +521,7 @@
 #include <__type_traits/aligned_union.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/aligned_union.h'}}
 #include <__type_traits/alignment_of.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/alignment_of.h'}}
 #include <__type_traits/apply_cv.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/apply_cv.h'}}
+#include <__type_traits/can_extract_key.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/can_extract_key.h'}}
 #include <__type_traits/common_reference.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/common_reference.h'}}
 #include <__type_traits/common_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/common_type.h'}}
 #include <__type_traits/conditional.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/conditional.h'}}
@@ -528,6 +529,7 @@
 #include <__type_traits/copy_cv.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/copy_cv.h'}}
 #include <__type_traits/copy_cvref.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/copy_cvref.h'}}
 #include <__type_traits/decay.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/decay.h'}}
+#include <__type_traits/dependent_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/dependent_type.h'}}
 #include <__type_traits/disjunction.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/disjunction.h'}}
 #include <__type_traits/enable_if.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/enable_if.h'}}
 #include <__type_traits/extent.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/extent.h'}}
@@ -542,6 +544,7 @@
 #include <__type_traits/is_base_of.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_base_of.h'}}
 #include <__type_traits/is_bounded_array.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_bounded_array.h'}}
 #include <__type_traits/is_callable.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_callable.h'}}
+#include <__type_traits/is_char_like_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_char_like_type.h'}}
 #include <__type_traits/is_class.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_class.h'}}
 #include <__type_traits/is_compound.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_compound.h'}}
 #include <__type_traits/is_const.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_const.h'}}
@@ -559,6 +562,7 @@
 #include <__type_traits/is_floating_point.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_floating_point.h'}}
 #include <__type_traits/is_function.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_function.h'}}
 #include <__type_traits/is_fundamental.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_fundamental.h'}}
+#include <__type_traits/is_implicitly_default_constructible.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_implicitly_default_constructible.h'}}
 #include <__type_traits/is_integral.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_integral.h'}}
 #include <__type_traits/is_literal_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_literal_type.h'}}
 #include <__type_traits/is_member_function_pointer.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_member_function_pointer.h'}}
@@ -590,6 +594,7 @@
 #include <__type_traits/is_signed.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_signed.h'}}
 #include <__type_traits/is_signed_integer.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_signed_integer.h'}}
 #include <__type_traits/is_standard_layout.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_standard_layout.h'}}
+#include <__type_traits/is_swappable.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_swappable.h'}}
 #include <__type_traits/is_trivial.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_trivial.h'}}
 #include <__type_traits/is_trivially_assignable.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_trivially_assignable.h'}}
 #include <__type_traits/is_trivially_constructible.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_trivially_constructible.h'}}
@@ -609,20 +614,24 @@
 #include <__type_traits/is_volatile.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/is_volatile.h'}}
 #include <__type_traits/lazy.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/lazy.h'}}
 #include <__type_traits/make_32_64_or_128_bit.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/make_32_64_or_128_bit.h'}}
+#include <__type_traits/make_const_lvalue_ref.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/make_const_lvalue_ref.h'}}
 #include <__type_traits/make_signed.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/make_signed.h'}}
 #include <__type_traits/make_unsigned.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/make_unsigned.h'}}
+#include <__type_traits/maybe_const.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/maybe_const.h'}}
 #include <__type_traits/nat.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/nat.h'}}
 #include <__type_traits/negation.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/negation.h'}}
 #include <__type_traits/promote.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/promote.h'}}
 #include <__type_traits/rank.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/rank.h'}}
 #include <__type_traits/remove_all_extents.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_all_extents.h'}}
 #include <__type_traits/remove_const.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_const.h'}}
+#include <__type_traits/remove_const_ref.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_const_ref.h'}}
 #include <__type_traits/remove_cv.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_cv.h'}}
 #include <__type_traits/remove_cvref.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_cvref.h'}}
 #include <__type_traits/remove_extent.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_extent.h'}}
 #include <__type_traits/remove_pointer.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_pointer.h'}}
 #include <__type_traits/remove_reference.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_reference.h'}}
 #include <__type_traits/remove_volatile.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/remove_volatile.h'}}
+#include <__type_traits/result_of.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/result_of.h'}}
 #include <__type_traits/type_identity.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/type_identity.h'}}
 #include <__type_traits/type_list.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/type_list.h'}}
 #include <__type_traits/underlying_type.h> // expected-error@*:* {{use of private header from outside its module: '__type_traits/underlying_type.h'}}
@@ -630,6 +639,7 @@
 #include <__utility/as_const.h> // expected-error@*:* {{use of private header from outside its module: '__utility/as_const.h'}}
 #include <__utility/auto_cast.h> // expected-error@*:* {{use of private header from outside its module: '__utility/auto_cast.h'}}
 #include <__utility/cmp.h> // expected-error@*:* {{use of private header from outside its module: '__utility/cmp.h'}}
+#include <__utility/convert_to_integral.h> // expected-error@*:* {{use of private header from outside its module: '__utility/convert_to_integral.h'}}
 #include <__utility/declval.h> // expected-error@*:* {{use of private header from outside its module: '__utility/declval.h'}}
 #include <__utility/exchange.h> // expected-error@*:* {{use of private header from outside its module: '__utility/exchange.h'}}
 #include <__utility/forward.h> // expected-error@*:* {{use of private header from outside its module: '__utility/forward.h'}}
diff --git a/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp b/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp
--- a/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp
+++ b/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp
@@ -16,6 +16,10 @@
 // Test that the __convert_to_integral functions properly converts Tp to the
 // correct type and value for integral, enum and user defined types.
 
+#include "test_macros.h"
+
+TEST_CLANG_DIAGNOSTIC_IGNORED("-Wprivate-header")
+#include <__utility/convert_to_integral.h>
 #include <limits>
 #include <type_traits>
 #include <cstdint>
@@ -23,8 +27,6 @@
 
 #include "user_defined_integral.h"
 
-#include "test_macros.h"
-
 template <class T>
 struct EnumType
 {
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp
@@ -16,6 +16,7 @@
 #include <algorithm>
 #include <cassert>
 #include <memory>
+#include <utility>
 
 #include "test_macros.h"
 #include "test_iterators.h"
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
--- a/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
@@ -17,9 +17,11 @@
 
 #include <array>
 #include <concepts>
+#include <functional>
 #include <iterator>
 #include <ranges>
 #include <random>
+#include <utility>
 
 #include "test_iterators.h"