Merge to upstream r225300.

Change-Id: I2b23715db9ac129ff80aa78ad5824db0a4d6fbb3

test/std/strings/basic.string.hash/strings.pass.cpp

@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <functional>
+
+// template <class T>
+// struct hash
+//     : public unary_function<T, size_t>
+// {
+//     size_t operator()(T val) const;
+// };
+
+// Not very portable
+
+#include <string>
+#include <cassert>
+#include <type_traits>
+
+template <class T>
+void
+test()
+{
+    typedef std::hash<T> H;
+    static_assert((std::is_base_of<std::unary_function<T, std::size_t>,
+                                   H>::value), "");
+    H h;
+    std::string g1 = "1234567890";
+    std::string g2 = "1234567891";
+    T s1(g1.begin(), g1.end());
+    T s2(g2.begin(), g2.end());
+    assert(h(s1) != h(s2));
+}
+
+int main()
+{
+    test<std::string>();
+#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
+    test<std::u16string>();
+    test<std::u32string>();
+#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
+    test<std::wstring>();
+}