def pro : Bool :=
let x := 42;
false
def f : Nat → Nat :=
fun x =>
  Nat.brecOn x fun x f =>
    (match (motive := (x : Nat) → Nat.below x → Nat) x with
      | 0 => fun x => 1
      | n.succ => fun x =>
        let y := 42;
        2 * x.1)
      f