private function optionalTypeHint() {
    static $array_callable_types = [T_ARRAY, T_CALLABLE];
    $node = NULL;
    if ($node = $this->tryMatchToken($array_callable_types)) {
      return $node;
    }
    elseif (in_array($this->currentType, self::$namespacePathTypes)) {
      return $this->name();
    }
    return NULL;
  }