unresolved import: `thiserror::Error`

[bryanburgers]

In the latest version of rust-analyzer (on nvim+coc, but a coworker is reporting the same thing on VSCode), I'm getting the following error from rust-analyzer.

[rust-analyzer] [E] unresolved import

This happens even though a regular build of the project finishes just fine.

thiserror::Error is a derive macro without an accompanying trait (c.f. serde::Serialize, which is a derive macro and also a trait, which does not cause an error).

Could there be a regression with importing derive macro traits?

[kbleeke]

I'm having a similar issue with snafu::Snafu (another error-handling derive macro)

[bjorn3]

You can enable proc-macro support using

{
    "rust-analyzer.cargo.loadOutDirsFromCheck": true,
    "rust-analyzer.procMacro.enable": true,
}

[Systemcluster]

I had the same issue with derive macro imports after the latest update with an existing project, but cleaning the target, rebuilding the project and reloading the editor solved it. I still don't get any information on hover (it's stuck at "Loading..."), but I don't know if that was already the case in the previous version.

[kbleeke]

You can enable proc-macro support using

{
    "rust-analyzer.cargo.loadOutDirsFromCheck": true,
    "rust-analyzer.procMacro.enable": true,
}

I thought, I had this enabled but apparently it was only in workspace settings of another workspace 🤦 . Fixed for me at least

[EverlastingBugstopper]

You can enable proc-macro support using

{
    "rust-analyzer.cargo.loadOutDirsFromCheck": true,
    "rust-analyzer.procMacro.enable": true,
}

This worked for me! Is there any reason this isn't enabled by default? It seems like this is a fairly common use case/language feature.

[lnicola]

It can be a security risk (you might load a project with a malicious build scripts), it slows down the first load of the project (because we need to compile them), it can slow down the analysis, it doesn't always work (because of ABI differences, e.g. proc macros don't work in nightly and beta right now and we can't fix them without breaking stable users they work since yesterday).

PS: cargo check is enabled by default, so maybe the security aspect is moot.

[bjorn3]

It can be a security risk (you might load a project with a malicious build scripts)

That already happens with cargo check.

[kellpossible]

You can enable proc-macro support using

Enabling those options worked for me but they made RA super slow to the point where I can't use it, and have to put up with the errors for now.

[bjorn3]

You can use "rust-analyzer.diagnostics.disabled": ["unresolved-import"] to disable the errors for this. It is already disabled in the latest version by default I think. (#6085)

[sunjay]

I seem to be getting the unresolved import error for thiserror::Error regardless of whether I have procMacro enabled. I am on rust-analyzer version: nightly (7b674f9).

[bjorn3]

Do you also have "rust-analyzer.cargo.loadOutDirsFromCheck": true?

[sunjay]

Yes. Sorry, I should have posted my config:

{
    "rust-analyzer.updates.channel": "nightly",
    "rust-analyzer.procMacro.enable": true,
    "rust-analyzer.cargo.loadOutDirsFromCheck": true,
    "rust-analyzer.inlayHints.parameterHints": false,
}

This just started happening today when I updated to the latest nightly. (My previous comment has the version)

[Ten0]

Same here. Additionally, it seems that cargo will stop checking at all if "rust-analyzer.cargo.loadOutDirsFromCheck": true,. (Though that may be more related to the fact my project is large?)
Note I didn't have these options enabled before, but enabling them did not fix this issue for me, it still shows the unresolved imports.

[lnicola]

@sunjay

I seem to be getting the unresolved import error for thiserror::Error regardless of whether I have procMacro enabled. I am on rust-analyzer version: nightly (7b674f9).

#5651

[Count-Count]

I worked around this issue thus:
use thiserror::*; // should be thiserror::Error, but https://github.com/rust-analyzer/rust-analyzer/issues/6053