sc_mult seems unnecessary
sc_mult field of
ApplyToVal seems not to be actually needed. It can always be obtained from
(m, _, _) = splitFunTy fun_ty
Eliminating it would give one less thing to get wrong.
Arnaud writes: "I'm pretty sure that this is correct, indeed. We evidently got sloppy in documenting what this multiplicity meant. I don't even remember why we needed this one. At any rate: now that there is a
sc_hole_ty it's fine to remove it :-)"