_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator& operator*() {return *this;}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator& operator++() {return *this;}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator operator++(int) {return *this;}
+
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Container* __get_container() const { return container; }
};
template <class _Container>
--- /dev/null
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// back_insert_iterator
+
+// _Container* __get_container(); // constexpr in C++20
+
+#include <iterator>
+#include <vector>
+
+#include "test_macros.h"
+#include "nasty_containers.h"
+#include "test_constexpr_container.h"
+
+template <class C>
+TEST_CONSTEXPR_CXX20 bool test(C c) {
+ const std::back_insert_iterator<C> i(c);
+ assert(i.__get_container() == std::addressof(c));
+ return true;
+}
+
+int main(int, char**) {
+ test(std::vector<int>());
+ test(nasty_vector<int>());
+#if TEST_STD_VER >= 20
+ test(ConstexprFixedCapacityDeque<int, 10>());
+ static_assert(test(ConstexprFixedCapacityDeque<int, 10>()));
+#endif
+ return 0;
+}