anchor.diff:   */
   class _ElementInfo {
     /**
  +   * TODO(scheglov) remove after fixing build flakiness on bots
  +   */
  +  final Element element;
  +
  +  /**
      * The identifier of the [CompilationUnitElement] containing this element.
      */
     final int unitId;
  
positive.code:    */
    int id;
  
    _ElementInfo(this.unitId, this.offset, this.kind);
  }
  
  /**
  
negative.code:    */
    UnitIndexBuilder assemble() {
      relations.sort((a, b) {
        if (a.elementInfo.id == null) {
          throw new StateError('No id for ${a.elementInfo.element}, '
              'location= ${a.elementInfo.element?.location}');
        }
        return a.elementInfo.id - b.elementInfo.id;
      });
      definedNames.sort((a, b) {
  