Remove unnecessary static_casts in std::forward_list

Author: winner245

libcxx/include/forward_list

@@ -296,7 +296,7 @@ struct __forward_node_traits {
 #  endif
 
   _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));
+    return static_cast<__begin_node_pointer>(__p);
   }
 };
 
@@ -363,12 +363,8 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_iterator {
 
   __begin_node_pointer __ptr_;
 
-  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
-    return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
-  }
-  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
-    return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
-  }
+  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const { return __ptr_; }
+  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const { return static_cast<__node_pointer>(__ptr_); }
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
 
@@ -427,12 +423,8 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator {
 
   __begin_node_pointer __ptr_;
 
-  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
-    return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
-  }
-  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
-    return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
-  }
+  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const { return __ptr_; }
+  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const { return static_cast<__node_pointer>(__ptr_); }
 
   _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}