[libc++] Remove unnecessary friend declarations from <__tree> (llvm#152133)

Removing the unnecessary friend declarations from `<__tree>` also
removes the need for forward declaration headers for `map` and `set`,
which this patch also removes.

Author: philnik777

libcxx/include/CMakeLists.txt

@@ -447,14 +447,12 @@ set(files
   __fwd/get.h
   __fwd/ios.h
   __fwd/istream.h
-  __fwd/map.h
   __fwd/mdspan.h
   __fwd/memory.h
   __fwd/memory_resource.h
   __fwd/ostream.h
   __fwd/pair.h
   __fwd/queue.h
-  __fwd/set.h
   __fwd/span.h
   __fwd/sstream.h
   __fwd/stack.h

libcxx/include/__fwd/map.h

@@ -13,9 +13,7 @@
 #include <__algorithm/min.h>
 #include <__assert>
 #include <__config>
-#include <__fwd/map.h>
 #include <__fwd/pair.h>
-#include <__fwd/set.h>
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
@@ -686,16 +684,6 @@ private:
   friend class __tree;
   template <class, class, class>
   friend class __tree_const_iterator;
-  template <class>
-  friend class __map_iterator;
-  template <class, class, class, class>
-  friend class map;
-  template <class, class, class, class>
-  friend class multimap;
-  template <class, class, class>
-  friend class set;
-  template <class, class, class>
-  friend class multiset;
 };
 
 template <class _Tp, class _NodePtr, class _DiffType>
@@ -709,18 +697,15 @@ class __tree_const_iterator {
   __end_node_pointer __ptr_;
 
 public:
-  using iterator_category = bidirectional_iterator_tag;
-  using value_type        = __get_node_value_type_t<_Tp>;
-  using difference_type   = _DiffType;
-  using reference         = const value_type&;
-  using pointer           = __rebind_pointer_t<_NodePtr, const value_type>;
+  using iterator_category                    = bidirectional_iterator_tag;
+  using value_type                           = __get_node_value_type_t<_Tp>;
+  using difference_type                      = _DiffType;
+  using reference                            = const value_type&;
+  using pointer                              = __rebind_pointer_t<_NodePtr, const value_type>;
+  using __non_const_iterator _LIBCPP_NODEBUG = __tree_iterator<_Tp, __node_pointer, difference_type>;
 
   _LIBCPP_HIDE_FROM_ABI __tree_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
 
-private:
-  typedef __tree_iterator<_Tp, __node_pointer, difference_type> __non_const_iterator;
-
-public:
   _LIBCPP_HIDE_FROM_ABI __tree_const_iterator(__non_const_iterator __p) _NOEXCEPT : __ptr_(__p.__ptr_) {}
 
   _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_np()->__value_; }
@@ -762,16 +747,6 @@ private:
 
   template <class, class, class>
   friend class __tree;
-  template <class, class, class, class>
-  friend class map;
-  template <class, class, class, class>
-  friend class multimap;
-  template <class, class, class>
-  friend class set;
-  template <class, class, class>
-  friend class multiset;
-  template <class>
-  friend class __map_const_iterator;
 };
 
 template <class _Tp, class _Compare>

libcxx/include/__fwd/set.h

@@ -582,7 +582,6 @@ erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
 #  include <__functional/binary_function.h>
 #  include <__functional/is_transparent.h>
 #  include <__functional/operations.h>
-#  include <__fwd/map.h>
 #  include <__iterator/erase_if_container.h>
 #  include <__iterator/iterator_traits.h>
 #  include <__iterator/ranges_iterator_traits.h>
@@ -861,7 +860,10 @@ public:
   friend class __tree_const_iterator;
 };
 
-template <class _Key, class _Tp, class _Compare, class _Allocator>
+template <class _Key, class _Tp, class _Compare = less<_Key>, class _Allocator = allocator<pair<const _Key, _Tp> > >
+class multimap;
+
+template <class _Key, class _Tp, class _Compare = less<_Key>, class _Allocator = allocator<pair<const _Key, _Tp> > >
 class map {
 public:
   // types:

libcxx/include/__tree

@@ -1607,7 +1607,6 @@ module std [system] {
   }
 
   module map {
-    module fwd { header "__fwd/map.h" }
     header "map"
     export *
     export std.iterator.reverse_iterator
@@ -1974,7 +1973,6 @@ module std [system] {
   }
 
   module set {
-    module fwd { header "__fwd/set.h" }
     header "set"
     export *
     export std.iterator.reverse_iterator

libcxx/include/map

@@ -522,7 +522,6 @@ erase_if(multiset<Key, Compare, Allocator>& c, Predicate pred);  // C++20
 #  include <__config>
 #  include <__functional/is_transparent.h>
 #  include <__functional/operations.h>
-#  include <__fwd/set.h>
 #  include <__iterator/erase_if_container.h>
 #  include <__iterator/iterator_traits.h>
 #  include <__iterator/ranges_iterator_traits.h>
@@ -570,7 +569,10 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Key, class _Compare, class _Allocator>
+template <class _Key, class _Compare = less<_Key>, class _Allocator = allocator<_Key> >
+class multiset;
+
+template <class _Key, class _Compare = less<_Key>, class _Allocator = allocator<_Key> >
 class set {
 public:
   // types: