proposition: Lemma demo_unfolds_folds : forall a b, a = Id(b) -> Dup a = 0 -> Dup b = Id(0+0).
proof: Proof. Proof using. intros. dup 2. unfolds Dup. demo. unfolds Id,Dup. subst b. folds (Dup a). demo. Qed.
imports: TLC(LibTactics) Coq.micromega.Lia