anchor.diff:  
     @override
     void visitPrefixExpression(PrefixExpression node) {
  -    _recordElementKindAndTokenType(
  -        'PrefixExpression (${node.operator})', node.operand);
  +    _recordDataForNode('PrefixExpression (${node.operator})', node.operand);
       _recordTypeMatch(node.operand);
       super.visitPrefixExpression(node);
     }
  
positive.code:   }
  
    /// Record the element kind of the element associated with the left-most
    /// identifier that is a child of the [node].
    void _recordElementKind(String context, AstNode node) {
      if (node != null) {
        var kind = _leftMostKind(node);
  
negative.code: 
    @override
    void visitSpreadElement(SpreadElement node) {
      _recordDataForNode('SpreadElement (expression)', node.expression);
      super.visitSpreadElement(node);
    }
  
  