proposition: Lemma PAlt_subst x y ρ : (PAlt x y)[ρ] = PAlt (x`[ρ]) (y`[ρ]).
proof: Proof. unfold PAlt. cbn. now asimpl. Qed.
imports: Undecidability.FOL.Utils.FullSyntax Undecidability.Synthetic(EnumerabilityFacts ListEnumerabilityFacts) List