--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction39.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,15 @@
+// { dg-options -std=c++17 }
+
+template <class T> struct A { };
+
+A<int> a;
+const A c = a;
+volatile A v = a;
+const volatile A cv = a;
+
+template <class,class> struct same;
+template <class T> struct same<T,T> {};
+
+same<decltype(c), const A<int>> s1;
+same<decltype(v), volatile A<int>> s2;
+same<decltype(cv), const volatile A<int>> s3;