const ArrayRef<int64_t> begin_shape = begin_type.getShape();
    const int begin_dim = begin_shape.size();

    if (begin_dim != 1) return failure();

    // The ellipsis fill might exceed the current output shape because we are
    // also taking account of any to-be-inserted new axes.
    const int ellipsis_filled_dim_size =
        input_size - begin_shape[0] + 1 + absl::popcount(new_axis_mask);