Fix for issue #6259: also look for subclasses when checking if a typed selector applies to an eleme…

tests/language/typed_selector_test.dart

Index: tests/language/typed_selector_test.dart
===================================================================
--- tests/language/typed_selector_test.dart	(revision 0)
+++ tests/language/typed_selector_test.dart	(revision 0)
@@ -0,0 +1,25 @@
+// 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.
+// Regression test for http://dartbug.com/6259.
+
+class A {
+  get document => 42;
+}
+
+abstract class B {
+  abstract get document;
+}
+
+class C extends A implements B {
+}
+
+int inscrutable(int x) => x == 0 ? 0 : x | inscrutable(x & (x - 1));
+
+void main() {
+  var tab = [new Object(), new C()];
+  var obj = tab[inscrutable(1)];
+  int res = 0;
+  if (obj is B) res = obj.document;
+  Expect.equals(42, res);
+}