if (handleNullAutomatically) {
      // TODO(kevinb): we shouldn't be checking for a null result at runtime. Assert?
      return a == null ? null : checkNotNull(doForward(a));
    } else {
      return unsafeDoForward(a);
    }
  }

  @Nullable A correctedDoBackward(@Nullable B b) {
    if (handleNullAutomatically) {
      // TODO(kevinb): we shouldn't be checking for a null result at runtime. Assert?