proposition: Lemma demo_forwards_2 : (forall x y : nat, x = y -> x <= y) -> forall a b : nat, a <= a.
proof: Proof. Proof using. intros. dup. forwards K: (H a). reflexivity. apply K. forwards* K: (H a). Qed.
imports: TLC(LibTactics) Coq.micromega.Lia