Hi everyone,
First of all, let me say that I am a big fan of Symfony and enjoy the new functionality introduced in Symfony 3.x, such as the Workflow Component, a great help!

I wanted to request a feature on the Workflow Component to support the use of ValueObjects for the marking store. I am a big fan of using ValueObjects to restrict the usage of otherwise potentially 'generic' properties. For example, I have the following YML:

framework:
  workflows:
    my_workflow:
      type: 'state_machine'
      supports:
        - AppBundle\Entity\MyEntity
      marking_store:
        type: 'single_state'
        arguments:
          - 'status'

The usage of the 'status' elsewhere in the application is guarded by the ValueObject MyStatus:

class MyStatus
{
 const STATUS_NEW = 'new';
 const STATUS_OTHER = 'other';

 /** @var string **/
 protected $status;

 public function __construct(string $status) {
  if(!in_array($status,self::getStatuses()) {
   throw new InvalidArgumentException();
  }
  $this->status = $status;
 }

 public function __toString()
 {
  return $this->status;
 }

 public function getStatuses()
 {
  return [
   self::STATUS_NEW,
   self::STATUS_OTHER
  ];
 }
}

This is then used in the MyEntity class:

...
/**
 * @var MyStatus
 */
protected $status;
...
public function __construct()
{
 $this->status = new MyStatus(MyStatus::NEW);
}
...

Currently, I get the following error when I try using a ValueObject:

ContextErrorException: Warning: Illegal offset type

Thrown in the SingleStateMarkingStore at line 52:

return new Marking(array($placeName => 1));

Could support for ValueObjects be realized by potentially doing a string cast?

return new Marking(array((string)$placeName => 1));

I hope I made my case clear and I'm not overlooking anything here that might indicate my feature request to be a non-issue or already available.

Thanks in advance,
Kind regards,
Mark