diff --git a/include/boost/fusion/support/category_of.hpp b/include/boost/fusion/support/category_of.hpp
index 92b0ea1b..7397c45a 100644
--- a/include/boost/fusion/support/category_of.hpp
+++ b/include/boost/fusion/support/category_of.hpp
@@ -8,7 +8,6 @@
 #define FUSION_CATEGORY_OF_07202005_0308
 
 #include <boost/fusion/support/config.hpp>
-#include <boost/fusion/support/detail/category_of.hpp>
 #include <boost/fusion/support/tag_of.hpp>
 #include <boost/type_traits/is_base_of.hpp>
 
@@ -44,7 +43,10 @@ namespace boost { namespace fusion
         struct category_of_impl
         {
             template<typename T>
-            struct apply : detail::fusion_category_of<T> {};
+            struct apply
+            {
+                typedef typename T::category type;
+            };
         };
 
         template <>
diff --git a/include/boost/fusion/support/config.hpp b/include/boost/fusion/support/config.hpp
index 5a0f572e..d27266ed 100644
--- a/include/boost/fusion/support/config.hpp
+++ b/include/boost/fusion/support/config.hpp
@@ -1,6 +1,6 @@
 /*=============================================================================
     Copyright (c) 2014 Eric Niebler
-    Copyright (c) 2014,2018 Kohei Takahashi
+    Copyright (c) 2014,2015,2018 Kohei Takahashi
 
     Distributed under the Boost Software License, Version 1.0. (See accompanying
     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -108,4 +108,12 @@ namespace std
         decltype parenthesized_expr ::type
 #endif
 
+
+// Workaround for GCC 4.6 that rejects defaulted function with noexcept.
+#if BOOST_WORKAROUND(BOOST_GCC, / 100 == 406)
+#   define BOOST_FUSION_NOEXCEPT_ON_DEFAULTED
+#else
+#   define BOOST_FUSION_NOEXCEPT_ON_DEFAULTED BOOST_NOEXCEPT
+#endif
+
 #endif
diff --git a/include/boost/fusion/support/detail/and.hpp b/include/boost/fusion/support/detail/and.hpp
index 1b310dda..42926cb1 100644
--- a/include/boost/fusion/support/detail/and.hpp
+++ b/include/boost/fusion/support/detail/and.hpp
@@ -1,5 +1,6 @@
 /*=============================================================================
     Copyright (c) 2016 Lee Clagett
+    Copyright (c) 2018 Kohei Takahashi
 
     Distributed under the Boost Software License, Version 1.0. (See accompanying
     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -8,6 +9,7 @@
 #define FUSION_AND_07152016_1625
 
 #include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
 #include <boost/type_traits/integral_constant.hpp>
 
 #if defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
@@ -15,6 +17,8 @@
 #endif
 
 namespace boost { namespace fusion { namespace detail {
+#if defined(BOOST_NO_CXX17_FOLD_EXPRESSIONS) \
+ || BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1913))
     template<typename ...Cond>
     struct and_impl : false_type {};
 
@@ -34,6 +38,10 @@ namespace boost { namespace fusion { namespace detail {
          recursive. */
     template<typename ...Cond>
     struct and_ : and_impl1<Cond::value...> {};
+#else
+    template <typename ...Cond>
+    struct and_ : integral_constant<bool, ((bool)Cond::value && ...)> {};
+#endif
 }}}
 
 #endif // FUSION_AND_07152016_1625
diff --git a/include/boost/fusion/support/detail/category_of.hpp b/include/boost/fusion/support/detail/category_of.hpp
deleted file mode 100644
index e7ac44e5..00000000
--- a/include/boost/fusion/support/detail/category_of.hpp
+++ /dev/null
@@ -1,19 +0,0 @@
-/*=============================================================================
-    Copyright (c) 2001-2011 Joel de Guzman
-
-    Distributed under the Boost Software License, Version 1.0. (See accompanying 
-    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-==============================================================================*/
-#if !defined(FUSION_CATEGORY_OF_07212005_1025)
-#define FUSION_CATEGORY_OF_07212005_1025
-
-namespace boost { namespace fusion { namespace detail
-{
-    template <typename T>
-    struct fusion_category_of
-    {
-        typedef typename T::category type;
-    };
-}}}
-
-#endif
diff --git a/include/boost/fusion/support/detail/is_mpl_sequence.hpp b/include/boost/fusion/support/detail/is_mpl_sequence.hpp
index 24b86624..16b6db12 100644
--- a/include/boost/fusion/support/detail/is_mpl_sequence.hpp
+++ b/include/boost/fusion/support/detail/is_mpl_sequence.hpp
@@ -9,19 +9,17 @@
 #define FUSION_DETAIL_IS_MPL_SEQUENCE_29122006_1105
 
 #include <boost/fusion/support/config.hpp>
-#include <boost/fusion/support/sequence_base.hpp>
+#include <boost/fusion/support/detail/is_native_fusion_sequence.hpp>
 #include <boost/mpl/is_sequence.hpp>
 #include <boost/mpl/and.hpp>
 #include <boost/mpl/not.hpp>
-#include <boost/type_traits/is_complete.hpp>
-#include <boost/type_traits/is_convertible.hpp>
 
 namespace boost { namespace fusion { namespace detail
 {
     template <typename T>
     struct is_mpl_sequence
         : mpl::and_<
-            mpl::not_<mpl::and_<is_complete<T>, is_convertible<T, from_sequence_convertible_type> > >
+            mpl::not_<is_native_fusion_sequence<T> >
           , mpl::is_sequence<T> >
     {};
 }}}
diff --git a/include/boost/fusion/support/detail/is_native_fusion_sequence.hpp b/include/boost/fusion/support/detail/is_native_fusion_sequence.hpp
new file mode 100644
index 00000000..189c784d
--- /dev/null
+++ b/include/boost/fusion/support/detail/is_native_fusion_sequence.hpp
@@ -0,0 +1,27 @@
+/*=============================================================================
+    Copyright (c) 2018 Kohei Takahashi
+
+    Distributed under the Boost Software License, Version 1.0. (See accompanying
+    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+==============================================================================*/
+#ifndef BOOST_FUSION_IS_NATIVE_FUSION_SEQUENCE
+#define BOOST_FUSION_IS_NATIVE_FUSION_SEQUENCE
+
+#include <boost/fusion/support/config.hpp>
+#include <boost/fusion/support/sequence_base.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/type_traits/is_complete.hpp>
+#include <boost/type_traits/is_convertible.hpp>
+
+namespace boost { namespace fusion { namespace detail
+{
+    template <typename Sequence>
+    struct is_native_fusion_sequence
+      : mpl::and_<
+          is_complete<Sequence>
+        , is_convertible<Sequence, detail::from_sequence_convertible_type>
+      >
+    {};
+}}}
+
+#endif
diff --git a/include/boost/fusion/support/detail/is_view.hpp b/include/boost/fusion/support/detail/is_view.hpp
deleted file mode 100644
index c518dfc4..00000000
--- a/include/boost/fusion/support/detail/is_view.hpp
+++ /dev/null
@@ -1,19 +0,0 @@
-/*=============================================================================
-    Copyright (c) 2001-2011 Joel de Guzman
-
-    Distributed under the Boost Software License, Version 1.0. (See accompanying 
-    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-==============================================================================*/
-#if !defined(FUSION_IS_VIEW_03202006_0018)
-#define FUSION_IS_VIEW_03202006_0018
-
-namespace boost { namespace fusion { namespace detail
-{
-    template <typename T>
-    struct fusion_is_view
-    {
-        typedef typename T::is_view type;
-    };
-}}}
-
-#endif
diff --git a/include/boost/fusion/support/detail/unknown_key.hpp b/include/boost/fusion/support/detail/unknown_key.hpp
deleted file mode 100644
index 9466b9c0..00000000
--- a/include/boost/fusion/support/detail/unknown_key.hpp
+++ /dev/null
@@ -1,16 +0,0 @@
-/*=============================================================================
-    Copyright (c) 2001-2011 Joel de Guzman
-
-    Distributed under the Boost Software License, Version 1.0. (See accompanying 
-    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-==============================================================================*/
-#if !defined(FUSION_UNKNOWN_KEY_09242005_1219)
-#define FUSION_UNKNOWN_KEY_09242005_1219
-
-namespace boost { namespace fusion { namespace detail
-{
-    template <int index>
-    struct unknown_key {};
-}}}
-
-#endif
diff --git a/include/boost/fusion/support/is_sequence.hpp b/include/boost/fusion/support/is_sequence.hpp
index af7c84e1..95a9423f 100644
--- a/include/boost/fusion/support/is_sequence.hpp
+++ b/include/boost/fusion/support/is_sequence.hpp
@@ -10,13 +10,10 @@
 #include <boost/fusion/support/config.hpp>
 #include <boost/fusion/support/sequence_base.hpp>
 #include <boost/fusion/support/tag_of.hpp>
-#include <boost/mpl/and.hpp>
+#include <boost/fusion/support/detail/is_native_fusion_sequence.hpp>
 #include <boost/mpl/bool.hpp>
 #include <boost/mpl/is_sequence.hpp>
-#include <boost/mpl/or.hpp>
-#include <boost/type_traits/is_complete.hpp>
 #include <boost/type_traits/is_convertible.hpp>
-#include <boost/type_traits/is_same.hpp>
 
 namespace boost { namespace fusion
 {
@@ -69,13 +66,7 @@ namespace boost { namespace fusion
             >
         {};
 
-        template <typename Sequence, typename Enable = void>
-        struct is_native_fusion_sequence
-          : mpl::and_<
-            is_complete<Sequence>,
-            is_convertible<Sequence, fusion::detail::from_sequence_convertible_type>
-          >
-        {};
+        using detail::is_native_fusion_sequence;
     }
 }}
 
diff --git a/include/boost/fusion/support/is_view.hpp b/include/boost/fusion/support/is_view.hpp
index c54e60e1..a6ca7259 100644
--- a/include/boost/fusion/support/is_view.hpp
+++ b/include/boost/fusion/support/is_view.hpp
@@ -9,7 +9,6 @@
 
 #include <boost/fusion/support/config.hpp>
 #include <boost/mpl/bool.hpp>
-#include <boost/fusion/support/detail/is_view.hpp>
 #include <boost/fusion/support/tag_of.hpp>
 
 namespace boost { namespace fusion
@@ -28,8 +27,9 @@ namespace boost { namespace fusion
         {
             template <typename T>
             struct apply
-                : detail::fusion_is_view<T>
-            {};
+            {
+                typedef typename T::is_view type;
+            };
         };
 
         template <>
diff --git a/include/boost/fusion/support/unused.hpp b/include/boost/fusion/support/unused.hpp
index 964839ab..c376d07f 100644
--- a/include/boost/fusion/support/unused.hpp
+++ b/include/boost/fusion/support/unused.hpp
@@ -1,5 +1,6 @@
 /*=============================================================================
     Copyright (c) 2001-2011 Joel de Guzman
+    Copyright (c) 2018 Kohei Takahashi
 
     Distributed under the Boost Software License, Version 1.0. (See accompanying
     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,7 +11,6 @@
 #include <boost/fusion/support/config.hpp>
 #include <iosfwd>
 
-#include <boost/config.hpp>
 #if defined(BOOST_MSVC)
 # pragma warning(push)
 # pragma warning(disable: 4522) // multiple assignment operators specified warning
@@ -23,9 +23,16 @@ namespace boost { namespace fusion
     struct unused_type
     {
         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        unused_type() BOOST_NOEXCEPT
+        BOOST_DEFAULTED_FUNCTION(
+        unused_type() BOOST_FUSION_NOEXCEPT_ON_DEFAULTED,
         {
-        }
+        })
+
+        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
+        BOOST_DEFAULTED_FUNCTION(
+        unused_type(unused_type const&) BOOST_FUSION_NOEXCEPT_ON_DEFAULTED,
+        {
+        })
 
         template <typename T>
         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
@@ -33,35 +40,12 @@ namespace boost { namespace fusion
         {
         }
 
-        template <typename T>
-        BOOST_FUSION_CONSTEXPR_THIS BOOST_FUSION_GPU_ENABLED
-        unused_type const&
-        operator=(T const&) const BOOST_NOEXCEPT
-        {
-            return *this;
-        }
-
-        template <typename T>
-        BOOST_CXX14_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        unused_type&
-        operator=(T const&) BOOST_NOEXCEPT
-        {
-            return *this;
-        }
-
         BOOST_FUSION_CONSTEXPR_THIS BOOST_FUSION_GPU_ENABLED
         unused_type const&
         operator=(unused_type const&) const BOOST_NOEXCEPT
         {
             return *this;
         }
-
-        BOOST_CXX14_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        unused_type&
-        operator=(unused_type const&) BOOST_NOEXCEPT
-        {
-            return *this;
-        }
     };
 
     BOOST_CONSTEXPR_OR_CONST unused_type unused = unused_type();
diff --git a/test/Jamfile b/test/Jamfile
index 9492e83f..9289033c 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -267,6 +267,7 @@ project
     [ compile support/and.cpp
         : [ requires cxx11_variadic_templates ] ]
     [ compile support/tag_of.cpp ]
+    [ compile support/unused.cpp ]
 
 #   [ compile-fail xxx.cpp  ]
 
diff --git a/test/support/unused.cpp b/test/support/unused.cpp
new file mode 100644
index 00000000..28d2ffda
--- /dev/null
+++ b/test/support/unused.cpp
@@ -0,0 +1,95 @@
+/*=============================================================================
+    Copyright (c) 2018 Kohei Takahashi
+
+    Distributed under the Boost Software License, Version 1.0. (See accompanying
+    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+==============================================================================*/
+
+#include <boost/config.hpp>
+#include <boost/fusion/support/unused.hpp>
+#include <boost/type_traits/detail/yes_no_type.hpp>
+#include <boost/static_assert.hpp>
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+#include <utility>
+#endif
+
+struct T { };
+
+void unused_construction()
+{
+    boost::fusion::unused_type dephault;
+
+    boost::fusion::unused_type BOOST_ATTRIBUTE_UNUSED parenthesis();
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    boost::fusion::unused_type BOOST_ATTRIBUTE_UNUSED brace{};
+    boost::fusion::unused_type BOOST_ATTRIBUTE_UNUSED list_copy = {};
+#endif
+
+    boost::fusion::unused_type copy_copy BOOST_ATTRIBUTE_UNUSED = dephault;
+    boost::fusion::unused_type copy_direct BOOST_ATTRIBUTE_UNUSED (dephault);
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    boost::fusion::unused_type copy_copy_brace_direct BOOST_ATTRIBUTE_UNUSED = {dephault};
+    boost::fusion::unused_type copy_direct_brace BOOST_ATTRIBUTE_UNUSED {dephault};
+#endif
+
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+    boost::fusion::unused_type move_copy BOOST_ATTRIBUTE_UNUSED = std::move(dephault);
+    boost::fusion::unused_type move_direct BOOST_ATTRIBUTE_UNUSED (std::move(dephault));
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    boost::fusion::unused_type move_copy_brace_direct BOOST_ATTRIBUTE_UNUSED = {std::move(dephault)};
+    boost::fusion::unused_type move_direct_brace BOOST_ATTRIBUTE_UNUSED {std::move(dephault)};
+#endif
+#endif
+
+
+    T value;
+
+    boost::fusion::unused_type T_copy_copy BOOST_ATTRIBUTE_UNUSED = value;
+    boost::fusion::unused_type T_copy_direct BOOST_ATTRIBUTE_UNUSED (value);
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    boost::fusion::unused_type T_copy_copy_brace_direct BOOST_ATTRIBUTE_UNUSED = {value};
+    boost::fusion::unused_type T_copy_direct_brace BOOST_ATTRIBUTE_UNUSED {value};
+#endif
+
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+    boost::fusion::unused_type T_move_copy BOOST_ATTRIBUTE_UNUSED = std::move(value);
+    boost::fusion::unused_type T_move_direct BOOST_ATTRIBUTE_UNUSED (std::move(value));
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    boost::fusion::unused_type T_move_copy_brace_direct BOOST_ATTRIBUTE_UNUSED = {std::move(value)};
+    boost::fusion::unused_type T_move_direct_brace BOOST_ATTRIBUTE_UNUSED {std::move(value)};
+#endif
+#endif
+}
+
+void unused_assignment()
+{
+    boost::fusion::unused_type val1, val2;
+
+    val1 = val2;
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+    val1 = {};
+#endif
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+    val1 = std::move(val2);
+#endif
+
+
+    T value;
+
+    val1 = value;
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+    val1 = std::move(value);
+#endif
+}
+
+boost::type_traits::yes_type test_unused(boost::fusion::detail::unused_only const&);
+boost::type_traits::no_type  test_unused(...);
+
+void only_unused()
+{
+    BOOST_STATIC_ASSERT((sizeof(test_unused(boost::fusion::unused)) == sizeof(boost::type_traits::yes_type)));
+    BOOST_STATIC_ASSERT((sizeof(test_unused(0)) == sizeof(boost::type_traits::no_type)));
+
+    boost::fusion::unused_type my_unused;
+    BOOST_STATIC_ASSERT((sizeof(test_unused(my_unused)) == sizeof(boost::type_traits::yes_type)));
+}