By catch on
Change record status: 
Published (View all published change records)
Project: 
Drupal core
Introduced in branch: 
9.1.x
Introduced in version: 
9.1.0
Issue links: 
https://www.drupal.org/node/3055194
Description: 

The signature of Symfony\Component\EventDispatcher\EventDispatcherInterface::dispatch() has changed.

Before:


$event_dispatcher->dispatch($event_name, Event $event = NULL);

After:


$event_dispatcher->dispatch(Event $event, $event_name = NULL);
Impacts: 
Module developers
Themers
Site templates, recipes and distribution developers