Rust-analyzer is extremely slow to index uom

[bheisler]

I'm working on a project which uses the uom crate. Rust-analyzer was always very slow to index this crate, but recently it's become unusable. Rust-analyzer has been stuck, pinning one CPU, on "indexing: 87/596 (uom)" for a full hour, and none of its usual features work until indexing is complete.

(I'm afraid I don't know precisely when this happened; I haven't worked on this project much since November. It was usable then.)

It does eventually work - in fact, it completed indexing as I'm typing this bug report - but an hour-long start-up time is not a great user experience. The rust-analyzer process is also using 1.7GB of memory.

I'm using version 0.2.513 of rust-analyzer in VSCode 1.54.1.

[Veykril]

The crate in question uses a lot of (heavily recursive?) mbe macros so I imagine this might have been caused by #7513
cc @edwin0cheng

[edwin0cheng]

Yeah, I think it is related to new mbe parser too. Still investigating what going on in Diesel case.

[phiresky]

Same for me. I've not yet seen rust analyzer complete indexing on my project, it's just stuck on uom. Reverting to 2021-02-01 fixes it

[edwin0cheng]

#7994 may fix it.

[edwin0cheng]

[triage] I tested it and it is not stuck now. However, there is some macro are not expanded correctly. Here is the test code :

use uom::si::f32::*;
use uom::si::length::kilometer;
use uom::si::time::second;

fn main() {
    let _length = Length::new::<kilometer>(5.0);
    let _time = Time::new::<second>(15.0);
 } 

[bheisler]

Yes, see also: #6537

[jonas-schievink]

Since the perf issue was fixed, closing this in favor of #6537