proposition: Lemma equiv_neq_var_const (x: nat) c: ~ var x ≡ const c.
proof: Proof. intros (v & ? & ?) % church_rosser; trivial. inv H; firstorder idtac using normal_var. inv H0. inv H. Qed.
imports: Morphisms Lia FinFun Undecidability.HOU(std.std) Undecidability.HOU.calculus(prelim terms syntax semantics confluence)