∀ {m : Type (max u_1 u_2) → Type u_3} {ε : Type (max u_1 u_2)} [inst : MonadAttach m] {α : Type (max u_1 u_2)}
  (x : ExceptT ε m α) (motive : (a : Except ε α) → MonadAttach.CanReturn x a → Sort u_4) (a : α)
  (h : MonadAttach.CanReturn x (Except.ok a))
  (h_1 : (a : α) → (h : MonadAttach.CanReturn x (Except.ok a)) → motive (Except.ok a) h)
  (h_2 : (e : ε) → (h : MonadAttach.CanReturn x (Except.error e)) → motive (Except.error e) h),
  (match Except.ok a, h with
    | Except.ok a, h => h_1 a h
    | Except.error e, h => h_2 e h) =
    h_1 a h