reducer is missing deleted members

[Pennycook]

SYCL 2020 explicitly deletes the following:

reducer(const reducer&) = delete;
reducer(reducer&&) = delete;
reducer& operator=(const reducer&) = delete;
reducer& operator=(reducer&&) = delete;

These are deleted to prevent mistakes. For example, the code below currently compiles with DPC++ but produces the wrong answer, because the lambda is passed a private copy of the reducer argument. The code is only correct if the final parameter is declared as auto& reducer.

q.parallel_for(sycl::range<1>{N}, sycl::reduction(sum, sycl::plus<>), [=](sycl::id<1>, auto reducer) {
  reducer++;
});

[Ali-Sed]

Hello,
I'd like to know if anyone else is working on this issue. If not, I'd be glad to work on it.
Thanks!

[aelovikov-intel]

AFAIK, I'm the only recent contributor to reductions and I'm not currently working on this.

This is something that I got bitten by a few times, so I'd be happy if you can contribute to it.

Thanks,
Andrei