re PR c++/68388 (incomplete type bug when using decltype)

2015-11-24  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/68388
	* g++.dg/cpp1y/pr68388.C: New.

From-SVN: r230827

gcc/testsuite/ChangeLog

+2015-11-24  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/68388
+	* g++.dg/cpp1y/pr68388.C: New.
+
 2015-11-24  Aditya Kumar  <aditya.k7@samsung.com>
 	    Sebastian Pop  <s.pop@samsung.com>
 

gcc/testsuite/g++.dg/cpp1y/pr68388.C

+// { dg-do compile { target c++14 } }
+
+namespace std {
+typedef int size_t;
+template <std::size_t... Indexes>
+struct index_sequence {};
+}
+
+template <class...> class Tuple {};
+
+template <std::size_t I, class TFirst>
+auto get(Tuple<TFirst>) {
+  return TFirst();
+}
+
+template <std::size_t I, class Functor, class T1, class T2>
+auto apply_impl(Functor f, T1 t1, T2 t2) {
+  return f(get<I>(t1), get<I>(t2));
+}
+
+template <std::size_t... Indexes, class Functor, class T1, class T2>        
+auto map_impl(std::index_sequence<Indexes...>, Functor f, T1 t1, T2 t2) {
+  Tuple<decltype(apply_impl<Indexes>(f, t1, t2))...>();
+}
+
+template <class Functor, class T1, class T2>
+auto map_impl(Functor f, T1 t1, T2 t2) {
+  map_impl(std::index_sequence<0>(), f, t1, t2);
+}
+                                 
+struct Less {                                                
+  template <class Lhs, class Rhs>                     
+  auto operator()(Lhs lhs, Rhs rhs) -> decltype(lhs < rhs) {
+    return lhs < rhs;
+  }
+};
+                                                                     
+int main() {
+  auto t1 = Tuple<int>();
+  auto t2 = Tuple<int>();
+  map_impl(Less(), t1, t2);
+}