operator<< improvements

test/optional_test_fail_io_without_io.cpp

@@ -0,0 +1,24 @@
+// Copyright (C) 2015, Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include <iostream>
+#include "boost/optional.hpp"
+// but no boost/optional/optional_io.hpp
+
+// THIS TEST SHOULD FAIL TO COMPILE
+// Unless one includes header boost/optional/optional_io.hpp, it should not be possible
+// to stream out an optional object.
+
+void test_streaming_out_optional()
+{
+  boost::optional<int> opt;
+  std::cout << opt;
+}