Léo NOEL

> Leo disagrees and I've forgotten his reasoning. * the mechanical difference is an implementation detail, the operator semantics are the same inside and outside `sp`/`ap` : run an effect,...

One alternative could be to detect the user error earlier, in this case `?` should be able to check that `ap` is not a task and raise an exception instead...

do you have a repro ?

Fixed in `b.39`