--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp0x/collapse-bug.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,16 @@
+// { dg-do compile { target c++11 } }
+template<typename T, typename U> struct same_type;
+template<typename T> struct same_type<T, T> {};
+
+template <typename T>
+struct S
+{
+  typedef T const (&type)();
+};
+
+void f()
+{
+  // initial implementation didn't ignore const qualifier on
+  // reference, resulting in a typedef of 'const int& (&)()'
+  same_type<S<int &>::type, int&(&)()>();
+}