1 files changed, 59 insertions, 0 deletions
diff --git a/libcxx/test/libcxx-03/iterators/unwrap_iter.pass.cpp b/libcxx/test/libcxx-03/iterators/unwrap_iter.pass.cpp
new file mode 100644
index 000000000000..8ef2be2b0107
--- /dev/null
+++ b/libcxx/test/libcxx-03/iterators/unwrap_iter.pass.cpp
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// check that std::__unwrap_iter() returns the correct type
+
+#include <algorithm>
+#include <cassert>
+#include <string>
+#include <type_traits>
+
+#include "test_iterators.h"
+#include "test_macros.h"
+
+template <class Iter>
+using UnwrapT = decltype(std::__unwrap_iter(std::declval<Iter>()));
+
+template <class Iter>
+using rev_iter = std::reverse_iterator<Iter>;
+
+template <class Iter>
+using rev_rev_iter = rev_iter<rev_iter<Iter> >;
+
+static_assert(std::is_same<UnwrapT<int*>, int*>::value, "");
+static_assert(std::is_same<UnwrapT<std::__wrap_iter<int*> >, int*>::value, "");
+static_assert(std::is_same<UnwrapT<rev_iter<int*> >, std::reverse_iterator<int*> >::value, "");
+static_assert(std::is_same<UnwrapT<rev_rev_iter<int*> >, int*>::value, "");
+static_assert(std::is_same<UnwrapT<rev_rev_iter<std::__wrap_iter<int*> > >, int*>::value, "");
+static_assert(std::is_same<UnwrapT<rev_rev_iter<rev_iter<std::__wrap_iter<int*> > > >, rev_iter<std::__wrap_iter<int*> > >::value, "");
+
+static_assert(std::is_same<UnwrapT<random_access_iterator<int*> >, random_access_iterator<int*> >::value, "");
+static_assert(std::is_same<UnwrapT<rev_iter<random_access_iterator<int*> > >, rev_iter<random_access_iterator<int*> > >::value, "");
+static_assert(std::is_same<UnwrapT<rev_rev_iter<random_access_iterator<int*> > >, random_access_iterator<int*> >::value, "");
+static_assert(std::is_same<UnwrapT<rev_rev_iter<rev_iter<random_access_iterator<int*> > > >, rev_iter<random_access_iterator<int*> > >::value, "");
+
+TEST_CONSTEXPR_CXX20 bool test() {
+  std::string str = "Banane";
+  using Iter = std::string::iterator;
+
+  assert(std::__unwrap_iter(str.begin()) == str.data());
+  assert(std::__unwrap_iter(str.end()) == str.data() + str.size());
+  assert(std::__unwrap_iter(rev_rev_iter<Iter>(rev_iter<Iter>(str.begin()))) == str.data());
+  assert(std::__unwrap_iter(rev_rev_iter<Iter>(rev_iter<Iter>(str.end()))) == str.data() + str.size());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 17
+  static_assert(test());
+#endif
+
+  return 0;
+}