add deconstructor in function argument

[TheIronBorn]

This matches things like this now:

struct Thing(u8, u8);

fn name(Thing(a, b): Thing) {
    do_something_with(a, b);
}

I don't know if this is the right way to solve it. Some more tests might also be in order

[jasonwilliams]

Some tests would be good @TheIronBorn

[jasonwilliams]

retry

[TheIronBorn]

Sorry. I've been slow on this because I found it breaks impl Trait parameters.

[jasonwilliams]

@TheIronBorn whats the update on this PR?

[jasonwilliams]

retry

[TheIronBorn]

I couldn't find a decent way to do this without just adding a lot of exceptions, or overhauling how we match function arguments.

Function arguments can be A LOT:

any pattern that is valid in a let binding is also valid as an argument

[TheIronBorn]

I suppose a place to start is a pattern binding syntax context.

[TheIronBorn]

There's some formal grammer for it here https://doc.rust-lang.org/grammar.html#variable-declarations. So I guess I'll start working on that.

Talked myself into it lol

[ehuss]

That grammar is pretty old. The following might provide better information on the grammar.

• The nightly version of the reference has more grammar rules in it: https://doc.rust-lang.org/nightly/reference/ It is making steady progress. The guy working on it also made an all-in-one page (though this might not be as current): https://brauliobz.github.io/rust-reference/grammar.html
• You might find some interesting information in the discussion for RFC 1331. There are links there for some other attempts at creating a grammar.
• The in-tree parser at https://github.com/rust-lang/rust/tree/master/src/grammar isn't too old (it was last updated last year), however it is not used or tested anywhere.

[TheIronBorn]

It would be really nice to reuse our other pattern matching code, but if we're going to be highlighting the parameter names as variable.parameter.rust I don't see how that's possible

[dten]

you can override things with a prototype, might work 😀

[TheIronBorn]

Something like:

prototype:
  - match: '{{identifier}}(?=:)'
    scope: variable.parameter

Hmm might work.