--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class2.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,17 @@
+// { dg-do compile { target c++2a } }
+
+struct A {
+  int i;
+  // auto operator<=> (const A&) = default;
+};
+template <typename T, T t> void f()
+{
+  g(t);				// { dg-error "not declared" }
+}
+
+int main()
+{
+  f<A,A{1}>();
+}
+
+// { dg-message "T t = A{1}" "" { target *-*-* } 0 }