proposition: Lemma f_eq {A B OA OB} {tA : t A OA} {tB : t B OB} {f : A -> B} : morph OA OB f -> Proper (eq ==> eq) f.
proof: Proof. unfold Proper, respectful. intros. apply (PO.f_eq (f_PO H)). assumption. Qed.
imports: SetoidClass Coq.Classes.Morphisms Coq.Arith.PeanoNat Fiat.Common.Coq__8_4__8_5__Compat