public function addAlias(...$alias) {
        foreach ($alias as $name) {
            $name = $this->normalizeID($name);

            if ($name === $this->currentRuleName) {
                trigger_error("Tried to set alias '$name' to self.", E_USER_NOTICE);
            } else {
                $this->rules[$name]['aliasOf'] = $this->currentRuleName;
            }
        }
        return $this;
    }