'cargo check --all-targets --workspace' fails on stable

[RalfJung]

Running cargo check --all-targets --workspace on stable fails with the following error:

error[E0554]: `#![feature]` may not be used on the stable release channel
 --> crossbeam-channel/benches/crossbeam.rs:1:12
  |
1 | #![feature(test)]
  |            ^^^^

    Checking crossbeam-queue v0.3.6 (/home/r/src/rust/lib-crates/crossbeam/crossbeam-queue)
For more information about this error, try `rustc --explain E0554`.
error: could not compile `crossbeam-channel` due to previous error

In particular this means opening crossbeam in vscode with rust-analyzer on a stable toolchain will show that error.

[taiki-e]

This is a common problem with all Rust crates running benchmarks using the built-in benchmark suite. A simple workaround is to use --tests --examples instead of --all-targets on stable.

I would accept a patch to use criterion in benchmarks, but there is no motivation on our part to address this since this situation is so common.

[RalfJung]

A simple workaround is to use --tests --examples instead of --all-targets on stable.

That doesn't help for vscode showing errors each time I open crossbeam.

[RalfJung]

Ah, putting this into the settings helps:

    "rust-analyzer.checkOnSave.overrideCommand": [
        "cargo", "check", "--lib", "--bins", "--tests", "--examples", "--workspace", "--message-format=json"
    ],

I wonder if this should be the default for RA...

[RalfJung]

Sadly that work-around doesn't work, since it will break on packages that don't have a libs crate.

I don't think there is a way right now to configure RA globally that would just make this work. :/

[taiki-e]

--tests should implicitly enable --lib if exists because the library must be built to build the test (--bins as well).

So, I think "--tests --examples instead of --all-targets" mentioned in the above comment should be enough.

[RalfJung]

The lib crate could have unit tests disabled though.

[taiki-e]

Unit tests don't seem disabled.

$ cargo new --lib repro
$ cd repro
$ echo '#[test]
fn a() {
    let _; // failed to compile
}
' > src/tests.rs
$ echo '#[cfg(test)] mod tests;' > src/lib.rs
$ cargo check --tests            
    Checking repro v0.1.0 (/Users/taiki/projects/tmp/c/repro)
error[E0282]: type annotations needed
 --> src/tests.rs:3:9
  |
3 |     let _; // failed to compile
  |         ^
  |
help: consider giving this pattern a type
  |
3 |     let _: _; // failed to compile
  |          +++

For more information about this error, try `rustc --explain E0282`.

[RalfJung]

But you can disable them in Cargo.toml

[lib]
test = false

[RalfJung]

FWIW for now I have simply pinned my crossbeam folder to a nightly rustc to work around this. Crossbeam so far is the only crate I have encountered that is affected by this. (I can believe that it is common, there are simply not that many crates I submit patches to, and of the around two dozen or so, crossbeam is the only one with this problem.)