feat(compiler): Allow arrays to do binary operation assignment

[renatoalencar]

Closes #1915

Following the same semantics as record set, array accesses should allow to make use of shorthand binary operation assignments like +=.

arr[0] += 1 currently throws a syntax error, this should fix it.

[ospencer]

Hey @renatoalencar! Apologies for the late response. This mostly looks good—would you mind adding a couple of tests for this?

[renatoalencar]

Hey @renatoalencar! Apologies for the late response. This mostly looks good—would you mind adding a couple of tests for this?

Sure, no problem. I'll add another tests, I'm not sure what would be nice to cover.

[ospencer]

I realized that we don't really have any tests that currently directly test regular binary assignments in the suite. Maybe some simple tests that just make sure we don't break it in the future; maybe one for each operator in https://github.com/grain-lang/grain/blob/d747d541dab3e2437c33fe224a92843f1027a226/compiler/test/suites/arrays.re.

[phated]

@ospencer can you help @renatoalencar with the parser exhaustiveness errors here?

[ospencer]

Done. This will also need support in the formatter, but I would wait for #1976 to land before attempting that.

[phated]

@ospencer does that mean you want to hold this PR or just open a follow up issue?

[ospencer]

We can open an issue.

[renatoalencar]

@ospencer can you help @renatoalencar with the parser exhaustiveness errors here?

I was about to get into Discord to ask for help on this

[ospencer]

Feel free to join us there! 😄