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/*!
@file
Defines `boost::hana::tag_of` and `boost::hana::tag_of_t`.
@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)
*/
#ifndef BOOST_HANA_CORE_TAG_OF_HPP
#define BOOST_HANA_CORE_TAG_OF_HPP
#include <boost/hana/fwd/core/tag_of.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename T, typename>
struct tag_of : tag_of<T, when<true>> { };
//! @endcond
namespace core_detail {
template <typename ...>
struct is_valid { static constexpr bool value = true; };
}
template <typename T, bool condition>
struct tag_of<T, when<condition>> {
using type = T;
};
template <typename T>
struct tag_of<T, when<
core_detail::is_valid<typename T::hana_tag>::value
>> {
using type = typename T::hana_tag;
};
template <typename T> struct tag_of<T const> : tag_of<T> { };
template <typename T> struct tag_of<T volatile> : tag_of<T> { };
template <typename T> struct tag_of<T const volatile> : tag_of<T> { };
template <typename T> struct tag_of<T&> : tag_of<T> { };
template <typename T> struct tag_of<T&&> : tag_of<T> { };
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_CORE_TAG_OF_HPP
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