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diff --git a/boost/hana/detail/type_at.hpp b/boost/hana/detail/type_at.hpp
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+/*!
+@file
+Defines `boost::hana::detail::type_at`.
+
+@copyright Louis Dionne 2013-2016
+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_DETAIL_TYPE_AT_HPP
+#define BOOST_HANA_DETAIL_TYPE_AT_HPP
+
+#include <boost/hana/config.hpp>
+
+#include <cstddef>
+#include <utility>
+
+
+// If possible, use an intrinsic provided by Clang
+#if defined(__has_builtin)
+#   if __has_builtin(__type_pack_element)
+#       define BOOST_HANA_USE_TYPE_PACK_ELEMENT_INTRINSIC
+#   endif
+#endif
+
+BOOST_HANA_NAMESPACE_BEGIN namespace detail {
+    namespace td {
+        template <std::size_t I, typename T>
+        struct elt { using type = T; };
+
+        template <typename Indices, typename ...T>
+        struct indexer;
+
+        template <std::size_t ...I, typename ...T>
+        struct indexer<std::index_sequence<I...>, T...>
+            : elt<I, T>...
+        { };
+
+        template <std::size_t I, typename T>
+        elt<I, T> get_elt(elt<I, T> const&);
+    }
+
+    //! @ingroup group-details
+    //! Classic MPL-style metafunction returning the nth element of a type
+    //! parameter pack.
+    template <std::size_t n, typename ...T>
+    struct type_at {
+#if defined(BOOST_HANA_USE_TYPE_PACK_ELEMENT_INTRINSIC)
+        using type = __type_pack_element<n, T...>;
+#else
+        using Indexer = td::indexer<std::make_index_sequence<sizeof...(T)>, T...>;
+        using type = typename decltype(td::get_elt<n>(Indexer{}))::type;
+#endif
+    };
+} BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_DETAIL_TYPE_AT_HPP