Merge to upstream r225300.

Change-Id: I2b23715db9ac129ff80aa78ad5824db0a4d6fbb3

test/std/re/re.regex/re.regex.assign/assign.pass.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <regex>
+
+// template <class charT, class traits = regex_traits<charT>> class basic_regex;
+
+// basic_regex& assign(const basic_regex& that);
+
+#include <regex>
+#include <cassert>
+
+int main()
+{
+    std::regex r1("(a([bc]))");
+    std::regex r2;
+    r2.assign(r1);
+    assert(r2.flags() == std::regex::ECMAScript);
+    assert(r2.mark_count() == 2);
+}