anchor.diff:      assert(_variableIndexer != null);
       _variableIndexer.pushScope();
       var oldLabels = _labelIndexer;
  -    _labelIndexer = new LabelIndexer();
  +    _labelIndexer = null;
       var oldCases = _switchCaseIndexer;
  -    _switchCaseIndexer = new SwitchCaseIndexer();
  +    _switchCaseIndexer = null;
       // Note: FunctionNode has no tag.
       _typeParameterIndexer.enter(node.typeParameters);
       writeOffset(node.fileOffset);
  
positive.code:   }
  
    visitSwitchStatement(SwitchStatement node) {
      _switchCaseIndexer.enter(node);
      writeByte(Tag.SwitchStatement);
      writeOffset(node.fileOffset);
  
negative.code:   }
  
    void writeNodeList(List<Node> nodes) {
      final len = nodes.length;
      writeUInt30(len);
      for (var i = 0; i < len; i++) {
        final node = nodes[i];
        writeNode(node);
      }
    }
  
    void writeNode(Node node) {
  