Multiple `#[test]` attributes run the test multiple times.

[Ethiraric]

If a function has multiple #[test] attributes, the test is run as many times as the attribute is repeated with cargo test.

The following code runs doing_the_thing 8 times:

mod tests {
    #[test]
    #[test]
    #[test]
    #[test]
    #[test]
    #[test]
    #[test]
    #[test]
    fn doing_the_thing() {}
}

fn main() {}

I expected to see this happen: The compiler errors

Instead, this happened: It compiles fine and the test is run 8 times

Meta

rustc --version --verbose:

rustc 1.56.1 (59eed8a2a 2021-11-01)
binary: rustc
commit-hash: 59eed8a2aac0230a8b53e89d4e99d55912ba6b35
commit-date: 2021-11-01
host: x86_64-unknown-linux-gnu
release: 1.56.1
LLVM version: 13.0.0

Happens on nightly as well:

rustc 1.58.0-nightly (d914f17ca 2021-11-16)
binary: rustc
commit-hash: d914f17ca71a33a89b2dc3436fca51b1a091559e
commit-date: 2021-11-16
host: x86_64-unknown-linux-gnu
release: 1.58.0-nightly
LLVM version: 13.0.0

cc @GuillaumeGomez

[GuillaumeGomez]

I think we should emit a warning in such case, that shouldn't be too complicated.

@Ethiraric said they would be interested into working on it so I'll assign them and help them implementing it.

[chaitanyav]

@GuillaumeGomez can i work on this one?.

[GuillaumeGomez]

No, as indicated in my message, @Ethiraric is already working on it.

EDIT: It was a bit rough I think so let me extend my initial message a bit: if you want to contribute, there are other E-easy and E-mentor issues. Don't hesitate to take a look there.

[ehuss]

FYI, PR #88681 is open to check for duplicate attributes. It doesn't handle test/bench because those are proc-macros, and it can be tricky to detect duplicates on those (see #88681 (comment)). So just a heads up this may not be particularly easy. I'm curious why it doesn't fail this check during subsequent passes.