- Just (tenv, dfun_id) -> do
-
- -- tenv is a substitution that instantiates the dfun_id
- -- to match the requested result type.
- --
- -- We ASSUME that the dfun is quantified over the very same tyvars
- -- that are bound by the tenv.
- --
- -- However, the dfun
- -- might have some tyvars that *only* appear in arguments
- -- dfun :: forall a b. C a b, Ord b => D [a]
- -- We instantiate b to a flexi type variable -- it'll presumably
- -- become fixed later via functional dependencies