anchor.diff:      EventHandler<XmlStartElementEvent>? onStartElement,
       EventHandler<XmlTextEvent>? onText,
     }) {
  -    final handler = _XmlForEachEventHandler(
  +    final handler = XmlEventHandler(
         onCDATA: onCDATA,
         onComment: onComment,
         onDeclaration: onDeclaration,
  
positive.code:     EventHandler<XmlStartElementEvent>? onStartElement,
      EventHandler<XmlTextEvent>? onText,
    }) {
      final handler = _XmlForEachEventHandler(
        onCDATA: onCDATA,
        onComment: onComment,
        onDeclaration: onDeclaration,
  
negative.code:       ).drain();
  }
  
  class XmlEventHandler with XmlEventVisitor {
    const XmlEventHandler({
      this.onCDATA,
      this.onComment,
      this.onDeclaration,
  