∀ {α : Type u_1} {x : BEq α} {x_1 : Hashable α} [inst : LawfulBEq α] {b : Std.ExtHashSet α}
  (motive : (a : Std.ExtHashSet α) → (a == b) = true → Prop) (a : Std.ExtHashSet α) (hyp : (a == b) = true),
  (∀ (inner : Std.ExtDHashMap α fun x => Unit) (hyp : ({ inner := { inner := inner } } == b) = true),
      motive { inner := { inner := inner } } hyp) →
    motive a hyp