anchor.diff:      return keys;
     }
   
  -  Future ensureIndex(String collectionName, {String key, Map keys, bool unique, bool sparse, bool background, bool dropDups, String name}) {
  -    return new Future.sync((){
  +  Future ensureIndex(String collectionName,
  +      {String key,
  +      Map keys,
  +      bool unique,
  +      bool sparse,
  +      bool background,
  +      bool dropDups,
  +      String name}) {
  +    return new Future.sync(() {
         keys = _setKeys(key, keys);
         return collection(collectionName).getIndexes().then((indexInfos) {
           if (name == null) {
  
positive.code:     });
    }
  
    executeMessage(MongoMessage message, WriteConcern writeConcern, {_Connection connection}) {
      if (state != State.OPEN) {
        throw new MongoDartError('DB is not open. $state');
      }
  
negative.code:   Future dropCollection(String collectionName) {
      return getCollectionInfos({'name': collectionName}).then((v) {
        if (v.length == 1) {
          return executeDbCommand(
              DbCommand.createDropCollectionCommand(this, collectionName));
        }
        return new Future.value(true);
      });
  