@SuppressWarnings("Unchecked")
  public static Object checkImmutable(Class<?> clazz, String fieldName, Object field) {
    Immutable immutable = (Immutable) clazz.getAnnotation(MY_CLASS);
    List<Class> knownImmutableClasses = new ArrayList<Class>();
    if (immutable != null && immutable.knownImmutableClasses().length > 0) {
      knownImmutableClasses = Arrays.asList(immutable.knownImmutableClasses());
    }

    if (field == null
        || field instanceof Enum
        || inImmutableList(field.getClass().getName())
        || knownImmutableClasses.contains(field.getClass())) return field;
    if (field instanceof Collection) return DefaultGroovyMethods.asImmutable((Collection) field);
    if (field.getClass().getAnnotation(MY_CLASS) != null) return field;
    final String typeName = field.getClass().getName();
    throw new RuntimeException(
        createErrorMessage(clazz.getName(), fieldName, typeName, "constructing"));
  }