Use `Natural` rather than `Integer` in `GHC.TypeLits`
When the numeric type-literals were implement via GHC.TypeLits
there was no Natural
type in base
yet. But since GHC 7.10 we finally have Natural
available in base!
Specifically, the following 3 type-signatures in GHC.TypeLits
contain Integer
s that ought rather be Natural
s:
someNatVal :: Integer -> Maybe SomeNat
natVal :: forall n proxy. KnownNat n => proxy n -> Integer
natVal' :: forall n. KnownNat n => Proxy# n -> Integer