Define traits::is_view for non fusion types

test/support/is_view.cpp

@@ -0,0 +1,15 @@
+/*=============================================================================
+    Copyright (c) 2018 Nikita Kniazev
+
+    Distributed under 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)
+==============================================================================*/
+#include <boost/fusion/support/is_view.hpp>
+#include <boost/static_assert.hpp>
+
+
+// Make sure fusion::is_view can be used with non fusion types.
+struct incomplete;
+BOOST_STATIC_ASSERT(!boost::fusion::traits::is_view<incomplete>::value);
+
+int main() { }