--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/gomp/udr-4.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,14 @@
+// { dg-do compile }
+
+struct S;					// { dg-message "forward declaration" }
+#pragma omp declare reduction (+:S:omp_out.s += omp_in.s) // { dg-error "incomplete type" }
+struct S { int s; S () : s (1) {} };
+#pragma omp declare reduction (*:S:omp_out.s *= omp_in.s)
+
+void
+foo ()
+{
+  S s;
+  #pragma omp parallel reduction (S::~S:s)	// { dg-error "invalid reduction-identifier" }
+  s.s = 1;
+}