-- For newtypes and closed type families (only) add the implicit coercion tycon
implicitCoTyCon :: TyCon -> [TyThing]
implicitCoTyCon tc
  | Just co <- newTyConCo_maybe tc = [ACoAxiom $ toBranchedAxiom co]
  | Just co <- isClosedSynFamilyTyConWithAxiom_maybe tc
                                   = [ACoAxiom co]
  | otherwise                      = []
implicitCoTyCon :: TyCon -> [TyThing]
implicitCoTyCon tc
  | Just co <- newTyConCo_maybe tc = [ACoAxiom $ toBranchedAxiom co]
  | Just co <- isClosedSynFamilyTyConWithAxiom_maybe tc
                                   = [ACoAxiom co]
  | otherwise                      = []
implicitCoTyCon tc
  | Just co <- newTyConCo_maybe tc = [ACoAxiom $ toBranchedAxiom co]
  | Just co <- isClosedSynFamilyTyConWithAxiom_maybe tc
                                   = [ACoAxiom co]
  | otherwise                      = []