Definition Node' (A: Type) (l: t A) (x: option A) (r: t A): t A :=
match l, x, r with
| Leaf, None, Leaf => Leaf
| _, _, _ => Node l x r
end.

(* Specifications: *)
Lemma gnode':
forall (A: Type) (l r: t A) (x: option A) (i: positive),
get i (Node' l x r) = get i (Node l x r).