Hi thanks for catching this problem!

While you're right that `supportsClass($class)` is incorrect here (`$class` should be a string and instead we're treating it as an object) simply instantiating an instance of the class to check is not quite right. If the User $class you're checking requires __construct() arguments, the instantiation of the class would fail and throw a fatal error.

A better check would be:

```php
public function supportsClass($class)
{
    return is_subclass_of($class, 'IMAG\LdapBundle\User\LdapUserInterface');
}
```

Can you please update your PR to use this implementation?