ex_tyvars' = [mkTyVar name (tyVarKind tv) | (name,tv) <- names `zip` ex_tyvars]
ex_tys' = mkTyVarTys ex_tyvars'
arg_tys = dataConArgTys con (inst_tys ++ ex_tys')
ex_tyvars' = [mkTyVar name (tyVarKind tv) | (name,tv) <- names `zip` ex_tyvars]
ex_tys' = mkTyVarTys ex_tyvars'
arg_tys = dataConArgTys con (inst_tys ++ ex_tys')