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:     return builder.namespaces[uri];
    }
  
    // Internal method to add something to the current element.
    void _insert(Object value) {
      if (value is Function) {
        value();
  
negative.code:         : new XmlName(name, _lookup(uri));
    }
  
    // Internal method to lookup an namespace prefix.
    String _lookup(String uri) {
      var builder = _stack.lastWhere(
        (builder) => builder.namespaces.containsKey(uri),
  