Unroll mp_append a bit.

include/boost/mp11/list.hpp

@@ -1,7 +1,7 @@
 #ifndef BOOST_MP11_LIST_HPP_INCLUDED
 #define BOOST_MP11_LIST_HPP_INCLUDED
 
-//  Copyright 2015 Peter Dimov.
+//  Copyright 2015-2017 Peter Dimov.
 //
 //  Distributed under the Boost Software License, Version 1.0.
 //
@@ -10,6 +10,8 @@
 
 #include <boost/mp11/integral.hpp>
 #include <boost/mp11/detail/mp_list.hpp>
+#include <boost/config.hpp>
+#include <boost/detail/workaround.hpp>
 
 namespace boost
 {
@@ -166,6 +168,28 @@ template<template<class...> class L1, class... T1, template<class...> class L2,
     using type = typename mp_append_impl<L1<T1..., T2...>, Lr...>::type;
 };
 
+#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, <= 1800 )
+#else
+
+template<
+    template<class...> class L1, class... T1,
+    template<class...> class L2, class... T2,
+    template<class...> class L3, class... T3,
+    template<class...> class L4, class... T4,
+    template<class...> class L5, class... T5,
+    template<class...> class L6, class... T6,
+    template<class...> class L7, class... T7,
+    template<class...> class L8, class... T8,
+    template<class...> class L9, class... T9,
+    template<class...> class L10, class... T10,
+    class... Lr>
+    struct mp_append_impl<L1<T1...>, L2<T2...>, L3<T3...>, L4<T4...>, L5<T5...>, L6<T6...>, L7<T7...>, L8<T8...>, L9<T9...>, L10<T10...>, Lr...>
+{
+    using type = typename mp_append_impl<L1<T1..., T2..., T3..., T4..., T5..., T6..., T7..., T8..., T9..., T10...>, Lr...>::type;
+};
+
+#endif
+
 } // namespace detail
 
 template<class... L> using mp_append = typename detail::mp_append_impl<L...>::type;

test/Jamfile.v2

@@ -25,6 +25,7 @@ run mp_push_front.cpp : : : $(REQ) ;
 run mp_push_back.cpp : : : $(REQ) ;
 run mp_rename.cpp : : : $(REQ) ;
 run mp_append.cpp : : : $(REQ) ;
+run mp_append_2.cpp : : : $(REQ) ;
 run mp_replace_front.cpp : : : $(REQ) ;
 run mp_replace_second.cpp : : : $(REQ) ;
 run mp_replace_third.cpp : : : $(REQ) ;

test/mp_append_2.cpp

@@ -0,0 +1,35 @@
+
+//  Copyright 2015 Peter Dimov.
+//
+// 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/core/lightweight_test_trait.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/mp11/algorithm.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+int main()
+{
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_append;
+    using boost::mp11::mp_iota_c;
+    using boost::mp11::mp_transform;
+    using boost::mp11::mp_rename;
+
+    using L1 = mp_iota_c<97>;
+    using L2 = mp_transform<mp_list, L1>;
+
+    using L3 = mp_rename<L2, mp_append>;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<L3, L1>));
+
+    //
+
+    return boost::report_errors();
+}