Implement positional-only arguments

[youknowone]

https://peps.python.org/pep-0570/

I know Violet is targeting Python 3.7 for now, but this is required to catch up the upper version later.

[LiarPrincess]

Ooo… nice!

I will go through this over the next few days. We just finished long weekend in Poland (1st and 3rd were national holidays) and things have piled up. I will also respond on the Swift forum.

[youknowone]

I wish you had a nice holiday!

[LiarPrincess]

Finished the review and for me it is ready for merge.

My changes:

• ran make elsa - this updates AST definition. Some comment has changed.
• ran make gen - I explained this on Swift forum, but long story short: swift does not have macros, decorators or annotations. However, there is an external tool for this: Sourcery. So, basically: if you create/change some sourcery annotation then you have to run make gen to update generated files.
• added tests for parser and compiler.

[LiarPrincess]

Can I merge or there is something more to do?

[youknowone]

wow, I didn't know I missed these many things. putting make elsa, make gen and checking diff to CI will be helpful for consistency.

[LiarPrincess]

You only missed make gen.

I wrote unit tests by hand, because I like be able to put a breakpoint and stop there in a few seconds (I once worked on a project in which the time between writing code and debugging was measured in minutes…). In general, I to try to exercise at least the main path, so that I know the runtime actually can get there. But unit tests are a 'bonus' feature.

And, yes I really need to work on the CI thing for Violet. Putting make elsa and make gen there is a nice idea. Though the main objective now is garbage collection.