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// Copyright Louis Dionne 2013-2017
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
#include <boost/hana/assert.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/not.hpp>
#include <boost/hana/optional.hpp>
#include <boost/hana/traits.hpp>
#include <boost/hana/type.hpp>
#include <type_traits>
#include <utility>
namespace hana = boost::hana;
template <typename ...>
using void_t = void;
template <typename T, typename = void>
struct has_type : std::false_type { };
template <typename T>
struct has_type<T, void_t<typename T::type>>
: std::true_type
{ };
auto common_type_impl = hana::sfinae([](auto t, auto u) -> hana::type<
decltype(true ? hana::traits::declval(t) : hana::traits::declval(u))
> { return {}; });
template <typename T, typename U>
using common_type = decltype(common_type_impl(hana::type_c<T>, hana::type_c<U>));
BOOST_HANA_CONSTANT_CHECK(
common_type_impl(hana::type_c<int>, hana::type_c<float>)
==
hana::just(hana::type_c<float>)
);
static_assert(!has_type<common_type<int, int*>>{}, "");
static_assert(std::is_same<common_type<int, float>::type, float>{}, "");
int main() { }
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