Hello. I’m trying to make a type family with resolving it inside type checking classes, like CmpNat. Its type signature is «type family Cmp (a :: k1) (b :: k2) :: Ordering», so the function is poly kinded. But it seems unclear how to make its TyCon. I’ve tried to follow the CmpNat and CmpSymbol style, and also saw Any TyCon in TysWiredIn. So this is my attempt: typeCmpTyCon :: TyCon typeCmpTyCon = mkFamilyTyCon name (binders ++ (mkTemplateAnonTyConBinders [ input_kind1, input_kind2 ])) orderingKind Nothing (BuiltInSynFamTyCon ops) Nothing NotInjective where name = mkWiredInTyConName UserSyntax gHC_TYPELITS (fsLit "Cmp") typeCmpTyFamNameKey typeCmpTyCon ops = BuiltInSynFamily { sfMatchFam = matchFamCmpType , sfInteractTop = interactTopCmpType , sfInteractInert = \_ _ _ _ -> [] } binders@[kv1, kv2] = mkTemplateKindTyConBinders [ liftedTypeKind, liftedTypeKind ] input_kind1 = mkTyVarTy (binderVar kv1) input_kind2 = mkTyVarTy (binderVar kv2) ghci says this: :kind Cmp Cmp :: forall {k0} {k1}. k0 -> k1 -> Ordering But then I try to apply it to some values and get this exception: :kind! Cmp 4 5 <interactive>:1:15: error: • Expected kind ‘k0’, but ‘4’ has kind ‘Nat’ • In the first argument of ‘Cmp’, namely ‘4’ In the type ‘Cmp 4 5’ <interactive>:1:17: error: • Expected kind ‘k1’, but ‘5’ has kind ‘Nat’ • In the second argument of ‘Cmp’, namely ‘5’ In the type ‘Cmp 4 5’ Does anyone know where I made a mistake? Any help would be appreciated.