proposition: Lemma equi_unifiable_refl s: [(s, s)] ≈ nil.
proof: Proof. intros ?; simplify; cbn; intuition (auto with relations). Qed.
imports: List Lia Arith Init.Wf Morphisms Program.Program Undecidability.HOU(concon.conservativity calculus.calculus) Undecidability.HOU.unification(systemunification nth_order_unification)