PR c++/85285 - ICE with flexible array after substitution.

	* pt.c (instantiate_class_template_1): Check for flexible array in
	union.

From-SVN: r259277

gcc/cp/ChangeLog

+2018-04-10  Jason Merrill  <jason@redhat.com>
+
+	PR c++/85285 - ICE with flexible array after substitution.
+	* pt.c (instantiate_class_template_1): Check for flexible array in
+	union.
+
 2018-04-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/85227

gcc/cp/pt.c

@@ -10904,6 +10904,14 @@ instantiate_class_template_1 (tree type)
 			      cxx_incomplete_type_error (r, rtype);
 			      TREE_TYPE (r) = error_mark_node;
 			    }
+			  else if (TREE_CODE (rtype) == ARRAY_TYPE
+				   && TYPE_DOMAIN (rtype) == NULL_TREE
+				   && (TREE_CODE (type) == UNION_TYPE
+				       || TREE_CODE (type) == QUAL_UNION_TYPE))
+			    {
+			      error ("flexible array member %qD in union", r);
+			      TREE_TYPE (r) = error_mark_node;
+			    }
 			}
 
 		      /* If it is a TYPE_DECL for a class-scoped ENUMERAL_TYPE,

gcc/testsuite/g++.dg/ext/flexary30.C

+// PR c++/85285
+
+template<typename T> union A
+{
+  T x;				// { dg-error "flexible array" }
+};
+
+A<int[]> a;