where `assert_never` is as discussed in
https://github.com/python/mypy/issues/5818.

I think it makes sense to discuss this use case with assert_never in the PEP

Of course, I would prefer to keep using Enums. That would require the
type checker to consider `Status` similarly to
`Literal[Status.Started, Status.Finished]`.

Yes, I think an enum should be equivalent to union of all its values. IIRC this is already required by PEP 484, but was never implemented.

We cab re-emphasize it in this PEP.

Ivan