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 <__function_like.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
 #include <concepts>
 #include <limits>
 #include <type_traits>
diff --git a/libcxx/include/__iterator/next.h b/libcxx/include/__iterator/next.h
--- a/libcxx/include/__iterator/next.h
+++ b/libcxx/include/__iterator/next.h
@@ -11,10 +11,13 @@
 #define _LIBCPP___ITERATOR_NEXT_H
 
 #include <__config>
+#include <__debug>
 #include <__function_like.h>
 #include <__iterator/advance.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
diff --git a/libcxx/include/__iterator/prev.h b/libcxx/include/__iterator/prev.h
--- a/libcxx/include/__iterator/prev.h
+++ b/libcxx/include/__iterator/prev.h
@@ -11,10 +11,13 @@
 #define _LIBCPP___ITERATOR_PREV_H
 
 #include <__config>
+#include <__debug>
 #include <__function_like.h>
 #include <__iterator/advance.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
diff --git a/libcxx/include/__memory/allocation_guard.h b/libcxx/include/__memory/allocation_guard.h
--- a/libcxx/include/__memory/allocation_guard.h
+++ b/libcxx/include/__memory/allocation_guard.h
@@ -13,6 +13,7 @@
 #include <__config>
 #include <__memory/allocator_traits.h>
 #include <cstddef>
+#include <utility>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
diff --git a/libcxx/include/__memory/allocator.h b/libcxx/include/__memory/allocator.h
--- a/libcxx/include/__memory/allocator.h
+++ b/libcxx/include/__memory/allocator.h
@@ -220,6 +220,9 @@
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return false;}
 
+template <class _Tp>
+struct __is_default_allocator<allocator<_Tp> > : true_type { };
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
diff --git a/libcxx/include/__memory/allocator_traits.h b/libcxx/include/__memory/allocator_traits.h
--- a/libcxx/include/__memory/allocator_traits.h
+++ b/libcxx/include/__memory/allocator_traits.h
@@ -361,9 +361,6 @@
 template <class _Tp>
 struct __is_default_allocator : false_type { };
 
-template <class _Tp>
-struct __is_default_allocator<allocator<_Tp> > : true_type { };
-
 // __is_cpp17_move_insertable
 template <class _Alloc, class = void>
 struct __is_cpp17_move_insertable
diff --git a/libcxx/include/__memory/pointer_safety.h b/libcxx/include/__memory/pointer_safety.h
--- a/libcxx/include/__memory/pointer_safety.h
+++ b/libcxx/include/__memory/pointer_safety.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___MEMORY_POINTER_SAFETY_H
 
 #include <__config>
+#include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
diff --git a/libcxx/include/__memory/pointer_traits.h b/libcxx/include/__memory/pointer_traits.h
--- a/libcxx/include/__memory/pointer_traits.h
+++ b/libcxx/include/__memory/pointer_traits.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___MEMORY_POINTER_TRAITS_H
 
 #include <__config>
+#include <__memory/addressof.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__ranges/access.h b/libcxx/include/__ranges/access.h
--- a/libcxx/include/__ranges/access.h
+++ b/libcxx/include/__ranges/access.h
@@ -11,7 +11,9 @@
 
 #include <__config>
 #include <__iterator/concepts.h>
+#include <__iterator/readable_traits.h>
 #include <__ranges/enable_borrowed_range.h>
+#include <concepts>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__ranges/concepts.h b/libcxx/include/__ranges/concepts.h
--- a/libcxx/include/__ranges/concepts.h
+++ b/libcxx/include/__ranges/concepts.h
@@ -11,9 +11,15 @@
 
 #include <__config>
 #include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/readable_traits.h>
 #include <__ranges/access.h>
+#include <__ranges/enable_borrowed_range.h>
 #include <__ranges/enable_view.h>
 #include <__ranges/size.h>
+#include <concepts>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__ranges/data.h b/libcxx/include/__ranges/data.h
--- a/libcxx/include/__ranges/data.h
+++ b/libcxx/include/__ranges/data.h
@@ -12,6 +12,7 @@
 #include <__config>
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
+#include <__memory/pointer_traits.h>
 #include <__ranges/access.h>
 #include <concepts>
 #include <type_traits>
diff --git a/libcxx/include/__ranges/empty.h b/libcxx/include/__ranges/empty.h
--- a/libcxx/include/__ranges/empty.h
+++ b/libcxx/include/__ranges/empty.h
@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__iterator/concepts.h>
+#include <__ranges/access.h>
 #include <__ranges/size.h>
 #include <type_traits>
 
diff --git a/libcxx/include/__ranges/size.h b/libcxx/include/__ranges/size.h
--- a/libcxx/include/__ranges/size.h
+++ b/libcxx/include/__ranges/size.h
@@ -13,6 +13,7 @@
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/access.h>
+#include <concepts>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__ranges/view_interface.h b/libcxx/include/__ranges/view_interface.h
--- a/libcxx/include/__ranges/view_interface.h
+++ b/libcxx/include/__ranges/view_interface.h
@@ -13,9 +13,12 @@
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/prev.h>
+#include <__memory/pointer_traits.h>
 #include <__ranges/access.h>
+#include <__ranges/concepts.h>
 #include <__ranges/empty.h>
 #include <__ranges/enable_view.h>
+#include <concepts>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)