From b5ba6cbd2b2ef54ef1a7d2c2ff59daeee22d1ef1 Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Sun, 14 Oct 2018 02:49:25 +0300
Subject: [PATCH] N3031 workaround for compilers without alias templates

---
 include/boost/fusion/support/config.hpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/boost/fusion/support/config.hpp b/include/boost/fusion/support/config.hpp
index ca3ce126..dc614d9d 100644
--- a/include/boost/fusion/support/config.hpp
+++ b/include/boost/fusion/support/config.hpp
@@ -101,6 +101,7 @@ namespace std
 #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1913)) || \
     BOOST_WORKAROUND(BOOST_GCC, < 40700) || \
     defined(BOOST_CLANG) && (__clang_major__ == 3 && __clang_minor__ == 0)
+# if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
 namespace boost { namespace fusion { namespace detail
 {
     template <typename T>
@@ -108,6 +109,11 @@ namespace boost { namespace fusion { namespace detail
 }}}
 #   define BOOST_FUSION_DECLTYPE_N3031(parenthesized_expr) \
         boost::fusion::detail::type_alias_t<decltype parenthesized_expr>
+# else
+#   include <boost/mpl/identity.hpp>
+#   define BOOST_FUSION_DECLTYPE_N3031(parenthesized_expr) \
+        boost::mpl::identity<decltype parenthesized_expr>::type
+# endif
 #else
 #   define BOOST_FUSION_DECLTYPE_N3031(parenthesized_expr) \
         decltype parenthesized_expr