@Contract("null -> false")
  public static boolean isTrait(@Nullable PsiClass aClass) {
    return aClass instanceof GrTypeDefinition && ((GrTypeDefinition)aClass).isTrait() ||
           aClass instanceof ClsClassImpl && aClass.isInterface() && AnnotationUtil.isAnnotated(aClass, GROOVY_TRAIT, 0) ||
           getDefaultMethods(aClass).length != 0;
  }
@Contract("null -> false")
  public static boolean isTrait(@Nullable PsiClass aClass)