Lemma istighttightapSet {X : tightapSet} : ∏ x y : X, ¬ (x ≠ y) → x = y. Proof. exact (pr2 (pr2 (pr2 X))). Qed.
Require Import UniMath.Foundations.Propositions. Require Import UniMath.MoreFoundations.Sets. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.MoreFoundations.DecidablePropositions.