1 // Copyright Louis Dionne 2013-2017
2 // Distributed under the Boost Software License, Version 1.0.
3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
5 #include <boost/hana/core/when.hpp>
6 namespace hana = boost::hana;
9 template <typename T, typename = hana::when<true>>
13 struct base_template<T, hana::when_valid<typename T::first_type>> { };
16 struct base_template<T, hana::when_valid<typename T::second_type>> { };
18 struct First { struct first_type; };
19 struct Second { struct second_type; };
21 template struct base_template<First>;
22 template struct base_template<Second>;