* The signature of the `EventDispatcherInterface::dispatch()` method has been changed to `dispatch($event, string $eventName = null): object`.
* The `Event` class has been removed in favor of `Symfony\Contracts\EventDispatcher\Event`.
* The `TraceableEventDispatcherInterface` has been removed.
* The `WrappedListener` class is now final.
4.4.0
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*`AddEventAliasesPass` has been added, allowing applications and bundles to extend the event alias mapping used by `RegisterListenersPass`.
* Made the `event` attribute of the `kernel.event_listener` tag optional for FQCN events.
4.3.0
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* The signature of the `EventDispatcherInterface::dispatch()` method should be updated to `dispatch($event, string $eventName = null)`, not doing so is deprecated
* deprecated the `Event` class, use `Symfony\Contracts\EventDispatcher\Event` instead
4.1.0
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* added support for invokable event listeners tagged with `kernel.event_listener` by default
* The `TraceableEventDispatcher::getOrphanedEvents()` method has been added.
* The `TraceableEventDispatcherInterface` has been deprecated.
4.0.0
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* removed the `ContainerAwareEventDispatcher` class
* added the `reset()` method to the `TraceableEventDispatcherInterface`