rust-analyzer unable to find rust-src after update to 0.3.2509

[ogapo]

rust-analyzer version: 0.3.2509 (NOTE: does not occur in 0.3.2500)

rustc version: rustc 1.88.0 (6b00bc388 2025-06-23)

editor or extension: VSCode rust-lang.rust-analyzer 0.3.2509 MacOS (aarm64)

relevant settings:
Not sure which of these is relevant but some quirks:

• project uses vendored dependencies (e.g. cargo vendor ./.cargo/vendor)
• project uses multi-root workspaces in VSCode
• project uses cargo workspaces

code snippet to reproduce:

Unfortunately I've yet to be able to repro this with a small project and I can't share the full repo. I've narrowed it down to specifically version 0.3.2509 in rust analyzer. Within that release, I'm a bit suspicious of #20047

The observed behavior is I get Problems such as "Variable None should have snake_case name, e.g. none [non_snake_case]" emitted and I cannot go to definition on any symbols in the rust standard library. This seems like it can't find rust-src. Cargo compiles fine though and rust-analyzer is able to go to definition properly on any symbols defined in my project or in any of the crates I'm importing. Wondering if perhaps the cargo check --compile-time-deps option is interacting poorly with the vendoring?

** workaround **

For now I can pin myself to 0.3.2500 but obviously it would be great to be able to take updates :-)

[ShoyuVanilla]

Both versions - 0.3.2509 and 0.3.2500 - are weeks old. Does this still happen with the latest releases?

[ogapo]

Yes, sorry I should have included that as well. I first noticed this when I upgraded today to the latest stable version (0.3.2539)

[ShoyuVanilla]

Could you check the output logs or rust analyzer warning messages? It's quite hard to infer the cause out of nothing. I'm suspicious of --compile-time-deps but that's activated only to toolchain >= 1.89.0, which is not our case (of course it might misbehave somehow).
Anyway, I guess rust-analyzer would be grumping something to logs.

[ogapo]

I was able to get this to reproduce with a small project when vendoring is enabled. Here's the log (from the latest stable version):
rust-analyzer-extension-log.txt

I don't see it complaining about anything in the logs, but it's very clearly linked to the vendor setup. If I run cargo vendor ./.cargo/vendor and then add

[source.crates-io]
replace-with = "vendored-sources"

[source.vendored-sources]
directory = "./.cargo/vendor"

to my .cargo/config.toml then I can no longer Go to Definition on any rust-src object (like String, None, etc) in my project.

Running mv .cargo .cargone and reloading rust-analyzer seems to fix the problem immediately.

[ShoyuVanilla]

Thanks! I'll look into this

[ShoyuVanilla]

I guess the problem is that:

1. Unlike normal cargo commands, rust-analyzer needs dependencies of std to work properly, like Go to Definitions on String. So, we fetch those dependencies when we start rust-analyzer
2. But those dependencies are not in Cargo.toml so cargo vendor doesn't vendor them into source.vendored-sources. Thus, we cannot fetch dependencies of std from source.vendored-sources and fails to analyze std properly

Not sure how to fix this in a quick thought but I'm sure we should implement something to handle cargo vendored things