(* coq-prog-args: ("-nois") *) Inductive eq {A : Type} (x : A) : forall a:A, Prop := eq_refl : eq x x. Axiom sym : forall A (x y : A) (_ : eq x y), eq y x. Require Import Ltac. Register eq as core.eq.type. Register sym as core.eq.sym. Goal forall A (x y:A) (_ : forall z, eq y z), eq x x. intros * H. replace x with y. - reflexivity. - apply H. Qed.