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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/pair.hpp>
#include <type_traits>
namespace hana = boost::hana;
struct empty1 { };
struct empty2 { };
struct empty3 { };
struct empty4 { };
// Make sure the storage of a pair is compressed
static_assert(sizeof(hana::pair<empty1, int>) == sizeof(int), "");
static_assert(sizeof(hana::pair<int, empty1>) == sizeof(int), "");
// Also make sure that a pair with only empty members is empty too. This is
// important to ensure, for example, that a tuple of pairs of empty objects
// will get the EBO.
static_assert(std::is_empty<hana::pair<empty1, empty2>>{}, "");
// Make sure that a pair of empty pairs is still empty.
static_assert(std::is_empty<
hana::pair<hana::pair<empty1, empty2>, empty3>
>{}, "");
static_assert(std::is_empty<
hana::pair<hana::pair<empty1, empty2>, hana::pair<empty3, empty4>>
>{}, "");
int main() { }
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