instaneceof *Type is rarely correct, and in this case it isn't :) You also need to account for mixed or bool being passed in here (so we cannot be sure if it's strict or not), so as always, isSuperTypeOf() wins :)

adapted, I think it should be more correct now? I still exit early the same way later though

This logic should be able to use isSuperTypeOf yes/no/maybe.

this is an edge case I think, it does already above to skip values for no, but here (with maybe|yes remaining) I want to mark maybe|yes as optional EXCEPT they are actually the same. example: filtering with bool makes the key with value true optional (because it's a supertype), but filtering with true should not make it optional (it's still a supertype though). does that make sense? I had a couple of such things already in the past, where I'm interested in basically $foo->isSuperTypeOf($bar)->yes() && !$foo->equals($bar)