Keep a trail while checking upper bounds in the VM in order to properly handle

tests/language/regress_25568_test.dart

Index: tests/language/regress_25568_test.dart
diff --git a/tests/language/regress_25568_test.dart b/tests/language/regress_25568_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6e18a60ed3759f7506ceb2b188bb53607ee46fd4
--- /dev/null
+++ b/tests/language/regress_25568_test.dart
@@ -0,0 +1,22 @@
+// Copyright (c) 2016, 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.
+
+main() {}
+
+class BacklogListEditorState
+    extends AbstractListEditorState<BacklogsState, BacklogListEditorState> {}
+
+class BacklogsState extends MutableEntityState<BacklogsState> {}
+
+abstract class AbstractListEditorState<ES extends ComponentState<ES>,
+    S extends AbstractListEditorState<ES, S>> extends ComponentState<S> {}
+
+abstract class ComponentState<S extends ComponentState<S>> {}
+
+abstract class EntityState<ES extends EntityState<ES>>
+    extends ComponentState<ES> {}
+
+abstract class MutableEntityState<S extends MutableEntityState<S>>
+    extends EntityState<S> implements ComponentState<S> {}
+