Add tests for tuple_for_each and empty tuples

include/boost/tuple_for_each.hpp

@@ -3,6 +3,7 @@
 
 #include <boost/integer_sequence.hpp>
 #include <boost/config.hpp>
+#include <boost/detail/workaround.hpp>
 #include <tuple>
 #include <utility>
 #include <type_traits>
@@ -20,6 +21,15 @@ template<class Tp, std::size_t... J, class F> BOOST_CONSTEXPR F tuple_for_each_i
     return (void)A{ ((void)f(std::get<J>(std::forward<Tp>(tp))), 0)... }, std::forward<F>(f);
 }
 
+#if BOOST_WORKAROUND( BOOST_MSVC, <= 1800 )
+
+template<class Tp, class F> BOOST_CONSTEXPR F tuple_for_each_impl( Tp && tp, boost::integer_sequence<std::size_t>, F && f )
+{
+    return std::forward<F>(f);
+}
+
+#endif
+
 } // namespace detail
 
 template<class Tp, class F> BOOST_CONSTEXPR F tuple_for_each( Tp && tp, F && f )

test/tuple_for_each.cpp

@@ -91,5 +91,19 @@ int main()
         }
     }
 
+    {
+        std::tuple<> tp;
+
+        BOOST_TEST_EQ( boost::tuple_for_each( tp, 11 ), 11 );
+        BOOST_TEST_EQ( boost::tuple_for_each( std::move( tp ), 12 ), 12 );
+    }
+
+    {
+        std::array<int, 0> tp;
+
+        BOOST_TEST_EQ( boost::tuple_for_each( tp, 11 ), 11 );
+        BOOST_TEST_EQ( boost::tuple_for_each( std::move( tp ), 12 ), 12 );
+    }
+
     return boost::report_errors();
 }

test/tuple_for_each_cx.cpp

@@ -31,9 +31,17 @@ struct assert_is_integral
 
 int main()
 {
-    constexpr std::tuple<int, short, char> tp{ 1, 2, 3 };
+    {
-    constexpr auto r = boost::tuple_for_each( tp, assert_is_integral() );
+        constexpr std::tuple<int, short, char> tp{ 1, 2, 3 };
-    (void)r;
+        constexpr auto r = boost::tuple_for_each( tp, assert_is_integral() );
+        (void)r;
+    }
+
+    {
+        constexpr std::tuple<> tp;
+        constexpr auto r = boost::tuple_for_each( tp, 11 );
+        static_assert( r == 11, "r == 11" );
+    }
 }
 
 #endif