Report errors and warnings for hiding elements, issue 572.

compiler/java/com/google/dart/compiler/resolver/ClassScope.java

Index: compiler/java/com/google/dart/compiler/resolver/ClassScope.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/ClassScope.java b/compiler/java/com/google/dart/compiler/resolver/ClassScope.java
index cba91e156ffed5e154b25c5edaea2de403a51a4e..13b694ca989d067a7eae47719ed6eb4c31204a8d 100644
--- a/compiler/java/com/google/dart/compiler/resolver/ClassScope.java
+++ b/compiler/java/com/google/dart/compiler/resolver/ClassScope.java
@@ -34,8 +34,13 @@ class ClassScope extends Scope {
       ClassScope scope = new ClassScope(superclass.getElement(),
                                         new Scope("library", (LibraryElement) enclosing));
       element = scope.findElement(inLibrary, name);
-      if (element != null) {
-        return element;
+      switch (ElementKind.of(element)) {
+        case TYPE_VARIABLE:
+          return null;
+        case NONE:
+          break;
+        default:
+          return element;
       }
     }
     for (InterfaceType supertype : classElement.getInterfaces()) {