proposition: Lemma substnn n t : subst n n t = lift 0 n t.
proof: Proof. funelim (subst n n t) ; try rewrite H ; try rewrite H0; simp lift; auto. rewrite Nat.compare_lt_iff in Heq; absurd lia. rewrite Nat.compare_gt_iff in Heq; absurd lia. Qed.
imports: Equations(Equations) Lia List Utf8 Arith Lia