public function performReadonlyTransformation()
    {
        $readonlyClassName = static::class . '_Readonly';

        if (ClassInfo::exists($readonlyClassName)) {
            $clone = $this->castedCopy($readonlyClassName);
        } else {
            $clone = $this->castedCopy(ReadonlyField::class);
        }

        $clone->setReadonly(true);

        return $clone;
    }