Support Phantom Types

[mchaver]

This might require base-4.10.0.0 to use Type Reflection and split a type into its kind size.
https://hackage.haskell.org/package/base-4.10.1.0/docs/Type-Reflection.html

proxyToTypeRep :: forall a. (Typeable a) => Proxy a -> TypeRep a
proxyToTypeRep Proxy = typeRep @a

typeRepKind $ proxyToTypeRep (Proxy :: Proxy Maybe)

[smurphy8]

This seems ambitious, though made easier with https://blog.janestreet.com/plans-for-ocaml-408/