Add test for a deleted default constructor

test/optional_test_deleted_default_ctor.cpp

@@ -0,0 +1,40 @@
+// Copyright 2017 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/config.hpp>
+
+#if defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
+
+int main()
+{
+}
+
+#else
+
+#include <boost/optional.hpp>
+
+template<class T1, class T2> struct pair
+{
+    T1 first;
+    T2 second;
+
+    pair(): first(), second()
+    {
+    }
+};
+
+struct A
+{
+    A() = delete;
+};
+
+int main()
+{
+    boost::optional< pair<A, int> > opt, opt2;
+    opt = opt2;
+}
+
+#endif