isTFHeaded ty | (TyConApp tc args) <- ty
              , isTypeFamilyTyCon tc
              = args `lengthIs` tyConArity tc
isTFHeaded ty | (TyConApp tc args) <- ty
              , isTypeFamilyTyCon tc
              = args `lengthIs` tyConArity tc
isTFHeaded ty | (TyConApp tc args) <- ty
              , isTypeFamilyTyCon tc
              = args `lengthIs` tyConArity tc