Implement LWG2367, SFINAE for tuple default constructor

STEllAR-GROUP · Apr 23, 2016 · caf9958 · caf9958
1 parent 6b65347
commit caf9958
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/hpx/util/tuple.hpp b/hpx/util/tuple.hpp
@@ -361,6 +361,13 @@ namespace hpx { namespace util
 
         // constexpr tuple();
         // Value initializes each element.
+        template <typename Delay = int, typename Enable =
+            typename std::enable_if<
+                detail::all_of<
+                    std::is_constructible<Delay>,
+                    std::is_constructible<Ts>...
+                >::value
+            >::type>
         HPX_CONSTEXPR tuple()
           : _impl()
         {}

diff --git a/tests/unit/util/tuple.cpp b/tests/unit/util/tuple.cpp
@@ -16,6 +16,7 @@
 #include "boost/type_traits/is_const.hpp"
 #include "boost/ref.hpp"
 #include <string>
+#include <type_traits>
 #include <utility>
 
 // ----------------------------------------------------------------------------
@@ -131,8 +132,8 @@ void construction_test()
     dummy(hpx::util::tuple<int, double>(1,3.14));
 
 
-    //dummy(hpx::util::tuple<double&>()); // should fail, not defaults for references
-    //dummy(hpx::util::tuple<const double&>()); // likewise
+    HPX_TEST(std::is_constructible<hpx::util::tuple<double&> >() == false);
+    HPX_TEST(std::is_constructible<hpx::util::tuple<const double&> >() == false);
 
     double dd = 5;
     dummy(hpx::util::tuple<double&>(dd)); // ok