induction n; intuition.
rewrite (vector_0 v2).
rewrite (vector_0 v1).
trivial.
destruct (vector_S v1).
destruct (vector_S v2).
destruct H0.
destruct H1.
subst.
unfold VectorDef.to_list in *.
inversion H; clear H; subst.
f_equal.
eauto.
Qed.

Lemma shiftOut_to_list : forall n (v : Bvector n),
shiftOut (VectorDef.to_list v) n = Some (v, nil).