I don't think you need an effect system. You just need to take care to correctly fiddle with some reference counts when an exception traverses your stack frame.

I don't think you need an effect system. You just need to take care to correctly fiddle with some reference counts when an exception traverses your stack frame. You already need to do that in other reference counted systems. After all, if an exception traverses your stack frame you need to decrement the reference counts of local variables. Whether or not you have checked exceptions or checked effects seems orthogonal to me. What matters is the implementation of those effects.