return (Class<? extends Annotation>) clazz;
    } else {
      throw new IllegalArgumentException(rootLocaleFormat("%s is not an annotation.", clazz));
    }
  }

  public void testFeatureEnums() throws Exception {
    assertGoodFeatureEnum(CollectionFeature.class);
    assertGoodFeatureEnum(ListFeature.class);
    assertGoodFeatureEnum(SetFeature.class);
    assertGoodFeatureEnum(CollectionSize.class);