proposition: Lemma dn_eqb (x y : bool) : ~~(x = y) -> x = y.
proof: Proof. destruct x, y; try congruence; intro H; exfalso; apply H; congruence. Qed.
imports: Coq.Lists.List Coq.ZArith.ZArith Coq.Lists.SetoidList Coq.Setoids.Setoid Coq.Classes.RelationClasses Coq.Program.Program Coq.Classes.Morphisms Fiat.Common.Tactics.SplitInContext Fiat.Common.Tactics.Combinators Fiat.Common.Tactics.FreeIn Fiat.Common.Tactics.SetoidSubst Fiat.Common.Tactics.BreakMatch Fiat.Common.Tactics.Head Fiat.Common.Tactics.FoldIsTrue Fiat.Common.Tactics.SpecializeBy Fiat.Common.Tactics.DestructHyps Fiat.Common.Tactics.DestructSig Fiat.Common.Tactics.DestructHead Fiat.Common.Coq__8_4__8_5__Compat