Manage Common Dependencies with Parent Services in symfony 3 - php

Question

I noticed a strange thing with managing common dependencies with parent services in symfony 3.1.6.
http://symfony.com/doc/current/service_container/parent_services.html
I try to define a user_manager service which extends fos user manager service.
// AppBundle/Service/UserManager.php
namespace AppBundle\Service;
use FOS\UserBundle\Doctrine\UserManager as BaseUserManager;
class UserManager extends BaseUserManager
{
}
// AppBundle/DependencyInjection/AppExtension.php
namespace AppBundle\DependencyInjection;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\Config\FileLocator;
use Symfony\Component\HttpKernel\DependencyInjection\Extension;
use Symfony\Component\DependencyInjection\Loader;
class AppExtension extends Extension
{
/**
* {#inheritdoc}
*/
public function load(array $configs, ContainerBuilder $container)
{
$loader = new Loader\YamlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
$loader->load('services.yml');
}
}
# AppBundle/Resources/config/services.yml
services:
app.user_manager:
class: AppBundle\Service\UserManager
parent: fos_user.user_manager.default
When trying to get service in contoller
$this->get('app.user_manager');
Then the exception is thrown:
'You have requested a non-existent service "app.user_manager".'
However, if I define my custom service in a different way:
# AppBundle/Resources/config/services.yml
services:
app.user_manager:
class: AppBundle\Service\UserManager
arguments:
- '#fos_user.util.password_updater'
- '#fos_user.util.canonical_fields_updater'
- '#fos_user.object_manager'
- '%fos_user.model.user.class%'
Then it works fine.
Moreover, it used to work like this with a "parent" before, in symfony 2.8
What could be wrong here and how it should be done properly with symfony 3.1?
p.s. I tried to clear cache, and also remove var/cache* directory, but that doesn't help