--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp1y/pr94066-2.C	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,19 @@
+// PR c++/94066
+// { dg-do compile { target c++14 } }
+
+struct A { long x; };
+
+union U;
+constexpr A foo(U *up);
+
+union U {
+  U() = default;
+  A a = foo(this); int y;
+};
+
+constexpr A foo(U *up) {
+  up->y = 11;  // { dg-error "'U::a' to 'U::y'" }
+  return {42};
+}
+
+extern constexpr U u = {};