Unable to click into include!'d sources; possibly spurious need-mut lint

[davidbarsky]

I'm trying out 14561—it's wonderful to be able to get definitions from protoc-generated code!—but unfortunately, I'm getting a bunch of need-mut errors from rust-analyzer at https://github.com/facebook/buck2/blob/f9e261bc956d48f587bfe6777b4de84ec1898bdc/app/buck2_data/src/lib.rs#L161.

(this could be a nightly toolchain-related thing or a prost-related thing; I haven't diagnosed this yet). I'm encountered two issues:

1. I can't click into the include!'d code. I'm guessing this might be followup work, but it'd be nice!
2. need-mut might be spurious, since rustc is seemingly fine with it.
   1. This might be related to prost more than anything.

rust-analyzer version: rust-analyzer version: 0.0.0 (901c8a4 2023-04-13)

rustc version: (eg. output of rustc -V) rustc 1.69.0-nightly (c8e6a9e8b 2023-01-23) (it's a RUSTC_BOOTSTRAP. long story.)

[Veykril]

I can't click into the include!'d code. I'm guessing this might be followup work, but it'd be nice!

If you mean not having any ide features in the included file, that's to be expected. Handling those as proper input will require #9403 and even with it, it's not 100% certain we'll be able to support that.

need-mut might be spurious, since rustc is seemingly fine with it.

Would be great if you could figure out a repro that causes it if it's not too much work (though I think we don't currently honor the corresponding rustc allow lint, so if thats used there than it might be expected)

[HKalbasi]

though I think we don't currently honor the corresponding rustc allow lint

That is for unused-mut, as need-mut is a hard error in rustc, so it is always a bug.

@davidbarsky my r-a doesn't work on buck2 repository, should I run something to generate rust-project.json?

[davidbarsky]

That is for unused-mut, as need-mut is a hard error in rustc, so it is always a bug.

gotcha.

@davidbarsky my r-a doesn't work on buck2 repository, should I run something to generate rust-project.json?

You shouldn't need to—I'd suggest cding into app/buck2_data/ and opening rust-analyzer there. Cargo should just work, as that's how I was able to discover this issue in the first place.

(I'm working on open-sourcing the tool that generates the rust-project.json right now. I'll let you know when it's out; it'll be under the buck2 repo.)

[HKalbasi]

Minimized:

fn x() {
    let x = &mut 2;
    || *x = 5;
}

[Veykril]

Ah, those are unique immutable borrows https://doc.rust-lang.org/stable/reference/types/closure.html#unique-immutable-borrows-in-captures

[davidbarsky]

If you mean not having any ide features in the included file, that's to be expected. Handling those as proper input will require #9403 and even with it, it's not 100% certain we'll be able to support that.

No, not that—I couldn't enter the file at all, but it seems to be working now. I think that functionality was fixed by #14576.

(I'm working on open-sourcing the tool that generates the rust-project.json right now. I'll let you know when it's out; it'll be under the buck2 repo.)

I've got it open-sourced yesterday here: https://github.com/facebook/buck2/tree/main/integrations/rust-project. There's some fb-specific stuff that lives there at the moment (e.g., locations of the sysroot) which I'll fix today.

Since the issues I've raised have been resolved, I'll close this out.