Fix issue 4562 by giving a proper error message rather than crashing.

tests/compiler/dart2js_extra/regress/4562_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-class Bound {
-  run() {
-    return 42;
-  }
+void main() {
+  var foo = new Foo();
+  var bar = new Bar(); /// 01: compile-time error
 }
 
-void main() {
-  var runner = new Bound().run;
-  Expect.equals(42, runner());
+class Foo {
+  factory Foo() => null;
 }
+
+class Bar extends Foo {
+  Bar(); /// 01: continued
+}