add a test for trac issue 8721

test/Jamfile.v2

@@ -10,6 +10,7 @@
 
 import testing ;
 
+local below_cpp11 = 98 03 ;
 local below_cpp14 = 98 03 0x 11 ;
 local since_cpp20 = 2a 20 latest ;
 
@@ -37,6 +38,7 @@ test-suite variant
     [ run variant_get_test.cpp ]
     [ compile-fail variant_rvalue_get_with_ampersand_test.cpp ]
     [ compile-fail no_rvalue_to_nonconst_visitation.cpp ]
+    [ compile fusion_interop.cpp : "<cxxstd>$(below_cpp11)"\:<build>no ]
     [ run variant_polymorphic_get_test.cpp ]
     [ run variant_multivisit_test.cpp ]
     [ run hash_variant_test.cpp ]

test/fusion_interop.cpp

@@ -0,0 +1,33 @@
+// Copyright (c) 2021 Antony Polukhin
+//
+// 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)
+
+// Test case from https://svn.boost.org/trac10/ticket/8721
+
+#include <boost/config.hpp>
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+
+#include <boost/variant.hpp>
+#include <boost/fusion/include/vector.hpp>
+
+struct emptyList {};
+
+typedef boost::make_recursive_variant
+  < emptyList
+  , boost::fusion::vector
+      < int
+      , boost::recursive_variant_
+      >
+  >::type IntList;
+
+const emptyList el = emptyList();
+const IntList nil( el );
+
+IntList cons( int head, IntList tail )
+{
+  return IntList( boost::fusion::vector<int, IntList>( head, tail ) );
+}
+
+#endif // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES