code: public function visitParameterList(ParameterList $parameterList)
      {
          $this->typeCheck->visitParameterList(func_get_args());
  
          $parameters = array();
          foreach ($parameterList->parameters() as $parameter) {
              $parameters[] = $parameter->accept($this);
          }
  
          return new ParameterList(
              $parameters,
              $parameterList->isVariableLength()
          );
      }
docs: @param ParameterList $parameterList
  
  @return mixed