I was trying to make a bridge like this

class MonadStateTF m where

type StateOf m :: *

instance (MonadState s m) => MonadStateTF m where

type StateOF m = s

to allow writing constraints on state monads without a dangling type parameter

type NumMonad m = (MonadStateTF m, Num (StateOf m))

Unfortunately, the declaration type StateOF m = s
complains that "s" isn't mentioned on the left hand side rather
than somehow making use of the fundep.

Brandon