This is used for Events whose handlers are expected to return something when called, similar to how many plugin events worked in earlier versions of Joomla.

This interface is partially implemented by the ResultAware trait. The typeCheckResult method is implemented by the various ResultTypeAware traits. Your event needs to use both the ResultAware trait and one of the ResultTypeAware traits. For example, if your event returns boolean results you need to use the ResultAware and ResultTypeBooleanAware traits in your event.