Fix designated initializer for anonymous union.

	* typeck2.c (process_init_constructor_record): Use
	init_list_type_node for the CONSTRUCTOR around an anonymous union
	designated initializer.

From-SVN: r258982

gcc/cp/ChangeLog

+2018-03-30  Jason Merrill  <jason@redhat.com>
+
+	* typeck2.c (process_init_constructor_record): Use
+	init_list_type_node for the CONSTRUCTOR around an anonymous union
+	designated initializer.
+
 2018-03-30  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/84791

gcc/cp/typeck2.c

@@ -1435,7 +1435,8 @@ process_init_constructor_record (tree type, tree init, int nested,
 		   designated-initializer-list { D }, where D is the
 		   designated-initializer-clause naming a member of the
 		   anonymous union object.  */
-		next = build_constructor_single (type, ce->index, ce->value);
+		next = build_constructor_single (init_list_type_node,
+						 ce->index, ce->value);
 	      else
 		{
 		  ce = NULL;

gcc/testsuite/g++.dg/cpp2a/desig9.C

+// { dg-do compile }
+// { dg-options "" }
+
+struct A {
+  union {
+    int a;
+    char b;
+  };
+};
+
+struct A x = {
+  .a = 5,
+};