Currently we are allowed firing generic events from javax.enterprise.event.Event<X>#fire as long as it's type parameter X does not contain a TypeVariable.
When it comes to javax.enterprise.inject.spi.BeanManager#fireEvent and javax.enterprise.inject.spi.BeanManager#resolveObserverMethods this is unfortunately not possible due to type erasure. Because we lack the relevant generic information that are otherwise explicit stated via Event#select, we are not able to fire a generic event from BeanManager#fireEvent.
This proposal is about enhancing the API of BeanManager in order to supply the relevant type information, that are otherwise discarded by type erasure. A possible solution would look like adding two new methods to BeanManager
which receive the selected event type as 1st parameter, validate that the actual event instance (2nd parameter) is assignable to the selected event type (the selected event type has to resolve all type variables; throwing an IllegalArgumentException otherwise) and fires the event afterwards.
The original two methods can delegate their calls to the new ones, having java.lang.Object as event type.
Additionally javax.enterprise.inject.spi.EventMetadata#getType() will return the resolved parameterized type.
With this proposal it would be possible to provide meta-extensions, that enable other extension to handle custom extension lifecycle events like