Fact cfun_inv0id : {in [predC cfun_unit], cfun_inv =1 id}.
Canonical cfAut_additive := Additive cfAut_is_rmorphism.
Canonical cfAut_rmorphism := RMorphism cfAut_is_rmorphism.

Lemma cfAut_cfun1 : cfAut 1 = 1. Proof. exact: rmorph1. Qed.