@Nullable
  private static PsiType getSuperReturnType(@NotNull PsiMethod superMethod) {
    if (superMethod instanceof GrMethod) {
      final GrTypeElement element = ((GrMethod)superMethod).getReturnTypeElementGroovy();
      return element != null ? element.getType() : null;
    }

    return superMethod.getReturnType();
  }
@Nullable
  private static PsiType getSuperReturnType(@NotNull PsiMethod superMethod)