The Permissions context in which this user should be filtered.
IRCUser.Class of the sender to filter.
Whether or not the sender's WHOIS result has expired (and thus may be reissued).
FilterResult.pass if the event should be allowed to trigger, FilterResult.whois if a WHOIS is required to tell and FilterResult.fail if the trigger should be denied.
Judges whether an event may be triggered, based on the event itself and the annotated Permissions of the handler in question. Implementation function.