public function user($id = null)
    {
        if ($this->allCleared === true || $this->isSwitchedOff()) {
            return;
        }

        if ($id === null) {
            // @todo From the looks of usage in legacy we only need to clear meta data here, and there is no such thing
            // in persistence so we ignore it for now.
            //$this->cache->clear();
        } elseif (is_scalar($id)) {
            $this->cache->invalidateTags(['user-' . $id]);
        } else {
            throw new InvalidArgumentType('$id', 'int|null', $id);
        }
    }