--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class8.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,26 @@
+// If the entity is a template parameter object for a template parameter of
+// type T, the type of the expression is const T.
+
+// { dg-do compile { target c++2a } }
+
+template <class T, class U> struct same;
+template <class T> struct same<T,T> {};
+
+struct A {
+  int i;
+  // auto operator<=> (const A&) = default;
+};
+void f(A&) = delete;
+void f(const A&) { }
+
+template < A a > struct B
+{
+  B()
+  {
+    f(a);
+    same<A,decltype(a)> s;
+    same<const A&,decltype((a))> s2;
+  }
+};
+
+B<A{42}> b;