anchor.diff:        assert(elements[node.receiver].isPrefix());
         // Hack: putting null into map overrides receiver of original node.
         collector.makeNullPlaceholder(node.receiver);
  +    }
  +  }
  +
  +  tryRenamePrivateSelector(Send node) {
  +    Identifier selector = node.selector.asIdentifier();
  +    assert(selector !== null);
  +    if (selector.source.isPrivate()) {
  +      collector.makePrivateIdentifier(selector);
       }
     }
   }
  
positive.code:     // element === null means dynamic property access.
      // We don't want to rename non top-level element access.
      if (element === null || !element.isTopLevel()) {
        tryRenamePrivateId(node);
        return;
      }
      // Unqualified <class> in static invocation, why it's not a type annotation?
  
negative.code:   visitForeignSend(Send node) {}
  
    visitDynamicSend(Send node) {
      tryRenamePrivateSelector(node);
    }
  
    visitGetterSend(Send node) {
  