private function functionCallParameter() {
    switch ($this->currentType) {
      case '&':
        return $this->writeVariable();
      case T_ELLIPSIS:
        $node = new SplatNode();
        $this->mustMatch(T_ELLIPSIS, $node);
        $node->addChild($this->expr(), 'expression');
        return $node;
      default:
        return $this->expr();
    }
  }