I am the deffilter macro, permitting inline succinct filter definitions. I take a module name (which becomes a child of the current module, e.g. deffilter Trivial inside EventBroker.Filters defines EventBroker.Filters.Trivial), and a do-block containing case patterns against which the event is matched and case bodies evaluating to true or false.

My optional parameters are parameter fields for the filter, annotated with their expected types.