freeVar :: Id -> TM ()
freeVar id = TM $ \ env st ->
                if id `elemVarSet` inScope env
                   then ((), unitOccEnv (nameOccName (idName id)) id, st)
                   else ((), noFVs, st)
freeVar :: Id -> TM ()
freeVar id = TM $ \ env st ->
                if id `elemVarSet` inScope env
                   then ((), unitOccEnv (nameOccName (idName id)) id, st)
                   else ((), noFVs, st)
freeVar id = TM $ \ env st ->
                if id `elemVarSet` inScope env
                   then ((), unitOccEnv (nameOccName (idName id)) id, st)
                   else ((), noFVs, st)