proposition: Lemma demo_gen_and_generalizes : forall P Q : nat -> nat -> nat -> Prop, forall a b c, P a b c -> Q a a a -> P b b c -> True.
proof: Proof. Proof using. intros. dup 3. gen H. demo. gen a. demo. gen b c. demo. Qed.
imports: TLC(LibTactics) Coq.micromega.Lia