[libc++] Remove identity casts in <{forward_,}list> (#130049)

Author: philnik777

libcxx/include/forward_list

@@ -295,7 +295,6 @@ struct __forward_node_traits {
                 "the _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB macro to silence this diagnostic.");
 #  endif
 
-  _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__begin_node_pointer __p) { return __p; }
   _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__node_pointer __p) {
     return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__p));
   }
@@ -373,8 +372,7 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_iterator {
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
 
-  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__begin_node_pointer __p) _NOEXCEPT
-      : __ptr_(__traits::__as_iter_node(__p)) {}
+  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__begin_node_pointer __p) _NOEXCEPT : __ptr_(__p) {}
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
       : __ptr_(__traits::__as_iter_node(__p)) {}
@@ -438,8 +436,7 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator {
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
 
-  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__begin_node_pointer __p) _NOEXCEPT
-      : __ptr_(__traits::__as_iter_node(__p)) {}
+  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__begin_node_pointer __p) _NOEXCEPT : __ptr_(__p) {}
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__node_pointer __p) _NOEXCEPT
       : __ptr_(__traits::__as_iter_node(__p)) {}

libcxx/include/list

@@ -286,12 +286,6 @@ struct __list_node_pointer_traits {
                 "LLVM 19 and LLVM 20. If you don't care about your ABI being broken, define the "
                 "_LIBCPP_ABI_LIST_REMOVE_NODE_POINTER_UB macro to silence this diagnostic.");
 #  endif
-
-  static _LIBCPP_HIDE_FROM_ABI __base_pointer __unsafe_link_pointer_cast(__base_pointer __p) { return __p; }
-
-  static _LIBCPP_HIDE_FROM_ABI __base_pointer __unsafe_link_pointer_cast(__node_pointer __p) {
-    return static_cast<__base_pointer>(static_cast<_VoidPtr>(__p));
-  }
 };
 
 template <class _Tp, class _VoidPtr>
@@ -504,7 +498,7 @@ protected:
   _LIBCPP_COMPRESSED_PAIR(size_type, __size_, __node_allocator, __node_alloc_);
 
   _LIBCPP_HIDE_FROM_ABI __base_pointer __end_as_link() const _NOEXCEPT {
-    return __node_pointer_traits::__unsafe_link_pointer_cast(const_cast<__node_base&>(__end_).__self());
+    return const_cast<__node_base&>(__end_).__self();
   }
 
   _LIBCPP_HIDE_FROM_ABI size_type __node_alloc_max_size() const _NOEXCEPT {