anchor.diff:    }
   
     Future<void> _addFix_removeEmptyCatch() async {
  -    // TODO(brianwilkerson) Determine whether this await is necessary.
  -    await null;
       var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(utils.getLinesRange(range.node(node.parent)));
  
positive.code: class DartFixContributor implements FixContributor {
    @override
    Future<List<Fix>> computeFixes(DartFixContext context) async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      try {
        FixProcessor processor = new FixProcessor(context);
        List<Fix> fixes = await processor.compute();
  
negative.code:   }
  
    Future<void> _addFix_createNoSuchMethod() async {
      if (node.parent is! ClassDeclaration) {
        return;
      }
  