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diff --git a/boost/hana/ext/boost/fusion/detail/common.hpp b/boost/hana/ext/boost/fusion/detail/common.hpp
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+/*!
+@file
+Defines common methods for all Boost.Fusion sequences.
+
+@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_EXT_BOOST_FUSION_DETAIL_COMMON_HPP
+#define BOOST_HANA_EXT_BOOST_FUSION_DETAIL_COMMON_HPP
+
+#include <boost/hana/bool.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+#include <boost/hana/fwd/at.hpp>
+#include <boost/hana/fwd/concept/sequence.hpp>
+#include <boost/hana/fwd/is_empty.hpp>
+#include <boost/hana/fwd/length.hpp>
+#include <boost/hana/integral_constant.hpp>
+
+#include <boost/fusion/sequence/intrinsic/at.hpp>
+#include <boost/fusion/sequence/intrinsic/empty.hpp>
+#include <boost/fusion/sequence/intrinsic/size.hpp>
+
+#include <cstddef>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    namespace detail {
+        template <typename T>
+        struct is_fusion_sequence {
+            static constexpr bool value = false;
+        };
+    }
+
+    //////////////////////////////////////////////////////////////////////////
+    // Iterable
+    //////////////////////////////////////////////////////////////////////////
+    template <typename S>
+    struct at_impl<S, when<detail::is_fusion_sequence<S>::value>> {
+        template <typename Xs, typename N>
+        static constexpr decltype(auto) apply(Xs&& xs, N const&) {
+            constexpr std::size_t n = N::value;
+            return boost::fusion::at_c<n>(static_cast<Xs&&>(xs));
+        }
+    };
+
+    template <typename S>
+    struct is_empty_impl<S, when<detail::is_fusion_sequence<S>::value>> {
+        template <typename Xs>
+        static constexpr auto apply(Xs&& xs) {
+            using Empty = decltype(boost::fusion::empty(xs));
+            return hana::bool_c<Empty::value>;
+        }
+    };
+
+    //////////////////////////////////////////////////////////////////////////
+    // Foldable
+    //////////////////////////////////////////////////////////////////////////
+    template <typename S>
+    struct length_impl<S, when<detail::is_fusion_sequence<S>::value>> {
+        template <typename Xs>
+        static constexpr auto apply(Xs const&) {
+            using Size = typename boost::fusion::result_of::size<Xs>::type;
+            return hana::size_c<Size::value>;
+        }
+    };
+
+    //////////////////////////////////////////////////////////////////////////
+    // Sequence
+    //////////////////////////////////////////////////////////////////////////
+    template <typename S>
+    struct Sequence<S, when<detail::is_fusion_sequence<S>::value>> {
+        static constexpr bool value = true;
+    };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_EXT_BOOST_FUSION_DETAIL_COMMON_HPP