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