anchor.diff:    void text(text) {
       var children = _stack.last.children;
       if (children.isNotEmpty && children.last is XmlText) {
  +      // merge consecutive text nodes into one
         var previous = children.removeLast();
         children.add(new XmlText(previous.text + text.toString()));
       } else {
  
positive.code:   /**
     * Binds a namespace `prefix` to the provided `uri`. The `prefix` can be
     * omitted to declare a default namespace. Throws an [ArgumentError] if
     * the `prefix` conflicts with an existing delcaration.
     */
    void namespace(String uri, [String prefix]) {
      if (prefix == _XMLNS || prefix == _XML) {
  
negative.code:     }
    }
  
  }
  
  abstract class _XmlNodeBuilder {
  