PS detects the class, but not its properties

I have a method that type hints a known class, and inside that method the properties of that class are marked as not found:

use App\Resource;
class Cache {
  function timesets(Resource $resource) {
    $this->set('timesets_' . $resource->club_id);
  }
}

/**
 * @property int $club_id
 */
class ActiveRecord {

}

class Resource extends ActiveRecord {
  function copy($name) {

  }
}

Inside Cache::timesets() PS knows that $resource is a App\Resource. But it doesn't know that $resource has a $club_id property or copy() method.

What also doesn't work:

* Adding the @property to Resource
* Adding a @param to Cache::timesets
* Adding a @var inside Cache::timesets

What's the problem? Clicking on Resource opens the right class. Hovering over $resource shows `Resource $resource : Resource`. Where does it go wrong? It does work for other classes here, and for Resource in other places.

Edit 1:

In other places, where Resource does work, the tooltip shows `$resource : App\Resource` so I guess it doesn't really detect the class in Cache::timesets()... A valid type hint should be enough, no?

Edit 2:

It looks like Resource is special... Maybe a reserved word or something? https://www.screencast.com/t/LptFXhvMji Both Club and Resource are imported, and valid classes, but only Club works... Resource only works indirectly, not as a type hint. Why??