{A : Type} {f : A -> A} (p : forall x, x = f x) {x y : A} (q : x = y) : (p x) @ (ap f q) = q @ (p y) := match q as i in (_ = y) return (p x @ ap f i = i @ p y) with | idpath => concat_p1_1p _ end.
Require Import Basics.Overture Basics.Tactics.