The distributed compiler sources do not come with an up-to-date lockfile

[RalfJung]

After installing the rustc-src component, trying to run cargo metadata on them will fail if the sources are installed in a read-only location (such as on Nix, or when cargo metadata is run in a sandbox). This could be avoided by either fixing cargo (rust-lang/cargo#10096), or by adjusting the rustc-src component to work around this behavior of cargo, by shipping an up-to-date lockfile.

Part of the problem seems to be that the cargo crates are not in a workspace any more when they are inside rustc-src. However, sadly, even if one puts a Cargo.toml (with all references to library/ and src/tools/ removed) into the right place, Cargo is still not happy with the lockfile -- it insists on removing everything unnecessary from this lockfile. So producing a lockfile that cargo is happy with could be rather tricky.

[jonhoo]

This feels somewhat-related to #95736

[RalfJung]

Yeah this is kind of the rustc-src version of that rust-src issue (note the rustc vs rust).

Somehow the rust-src issue doesn't seem to affect rust-analyzer or it has another way to work on a read-only file system; it's only with rustc-src that I am having trouble.

[jonhoo]

Now that you mention it, I seem to remember there's some special handling for rust-src in RA iirc for exactly this reason 🤔