Autocompletion does not work for function-local variable when there is a macro on a function

[gyzerok]

Hello everyone! Love the work you are doing for the community!

Setup

VSCode plugin: v0.2.817
Rust: 1.56.1 (59eed8a2a 2021-11-01)
Cargo: 1.56.0 (4ed5d137b 2021-10-04)
Rust Analyzer: 73668334f 2021-11-15 stable

Problem

I can confirm it happening in NeoVim as well, so it's not unique to VSCode setup.

Screen.Recording.2021-11-17.at.18.34.58.mov

Reproduction

Here is the smallest reproducable example I can get:

1. Do cargo init rust-analyzer-autocomplete-bug
2. Do cargo add tracing
3. Add following to your main.rs and try to type test where comment is
4. Observe things not working
5. Remove #[tracing::instrument] and try again to type test where comment is
6. Observe everything working fine

// main.rs
use std::collections::HashSet;

fn main() {
    println!("Hello, world!");
}

struct Test;

impl Test {
    fn test() -> HashSet<String> {
        HashSet::new()
    }
}

#[tracing::instrument]
async fn buggy_autocomplete() {
    let test = Test::test();
    // cannot autocomplete test here
}

I'd be happy to provide any additional details if needed. Really am excited about your project getting better every weak! 🎉

[gyzerok]

Hello @jonas-schievink! Do you need some extra information for the issue to become actionable?

[ngryman]

It seems to only break on full path macro names.

This breaks:

However, this works:

[Veykril]

It seems to only break on full path macro names.

That one is actually due to us always resolving #[test] to the builtin test attribute, which is fixed in current nightly/next stable.

So your problem is probably the async_std attributes not being input error tolerant, same probably for the tracing ones(though I think they fixed that so it might be something else there).

[Veykril]

Filed async-rs/async-std#998 for the async-std problem.

Regarding the original issue, this is interesting, typing just t gives the me autocompletion for test, but if I type te it disappears.

[ngryman]

I don't know if that helps but it happens with async-trait as well.
I'm pretty sure auto-completion was working there in previous versions of rust-analyzer.

[lnicola]

All proc macros using syn have this problem, unless they handle it as a special case. See dtolnay/async-trait#178 for async-trait.

[ngryman]

Meanwhile, for folks interested in bringing back the auto-completion, unchecking the Proc Attr Macros option made it work for me.

Given the fact that this option breaks auto-completion with what seems to be a good number of macros out there, and it's marked as "experimental", shouldn't it be an opt-in instead of an opt-out?

[lnicola]

We should probably remove the "experimental" bit. The problem is that the macro crashes on invalid input, which is what you have while typing code.

[ngryman]

@lnicola Thanks for the additional context 👍

In the current state of things, wouldn't that be more beneficial for the average user to disable it by default?