// TODO(cpovirk): consider manual binary search under GWT to preserve O(log N) lookup
  @Override
  public int indexOf(@Nullable Object target) {
    int index = delegateCollection().indexOf(target);

    // TODO(kevinb): reconsider if it's really worth making feeble attempts at
    // sanity for inconsistent comparators.

    // The equals() check is needed when the comparator isn't compatible with
    // equals().