Special cases in iterable unpacking

[scoder]

These came up in CPython issue 34508. We should make sure that we support them as well, and follow whatever they decide over there.

    def f(): return *(1, 2), 3

    eval('*(1, 2), 3')

    a = []; a += *(1, 2), 3

    for i in *(1, 2), 3: pass

    def g(): yield *(1, 2), 3

1. write tests and find out if they work or not, see the extended_unpacking tests.
2. find the places in the parser (Parsing.py) where these are disallowed, see the hacker guide
3. fix the parsing issues, find out what else is not working for whatever reason.

Don't hesitate to submit an incomplete PR and ask for further guidance.

[saksham-s1ngh]

Can I try working on this issue and ask to be assigned on it?

I'm new to open-source and as such, hope this is the correct way to work on open issues?

[da-woods]

Feel free to work on it and to ask if you have any issues.

We don't normally assign issues here mainly because most "I'd like to work on this" requests don't end up coming to anything. I'm pretty confident that nobody else is currently doing anything with this issue right now.