∀ {α : Type u_1} {dflt : α} (x : ℕ)
  (f :
    Nat.below (motive := fun x =>
      ∀ {acc : Array α} (x_1 : List α), List.takeDTR.go dflt x x_1 acc = acc.toList ++ List.takeD x x_1 dflt) x)
  {acc : Array α} (x_1 : List α), List.takeDTR.go dflt x x_1 acc = acc.toList ++ List.takeD x x_1 dflt