Newline in assignment causes false negative in `undocumented_unsafe_blocks`

[joshlf]

Summary

When a newline separates the = sign and the beginning of an unsafe block (as rustfmt sometimes produces), Clippy doesn't recognize a safety comment as decorating the unsafe block:

// SAFETY: ...
let x =
    unsafe { ... };

Lint Name

undocumented_unsafe_blocks

Reproducer

I tried this code:

#![deny(clippy::undocumented_unsafe_blocks)]

fn main() {
    // SAFETY: No unsafe code here!
    let _x =
        unsafe { 0 };
    // SAFETY: No unsafe code here!
    let _y = unsafe { 0 };
}

I expected to see this happen:

Both unsafe blocks should have been recognized as having a safety comment.

Instead, this happened:

undocumented_unsafe_blocks fired on let _x = ....

Version

1.72 (stable)

[y21]

The expected behavior is behind a configuration option. Setting accept-comment-above-statement = true in clippy.toml makes it recognize both safety comments and not lint.
(Also, this would be a FP, wouldn't it? It lints on code where it shouldn't)

[joshlf]

The expected behavior is behind a configuration option. Setting accept-comment-above-statement = true in clippy.toml makes it recognize both safety comments and not lint. (Also, this would be a FP, wouldn't it? It lints on code where it shouldn't)

Okay great, thanks!

And yeah, I should have said false positive - I guess I meant that the false negative was failing to notice the safety comment.

[Alexendoo]

Is there a reason that isn't on by default?

edit: #10832 (comment)

[Centri3]

There's #11170 which changes both to true. Looks like it just needs a collect-metadata run

[Alexendoo]

Nice, fixed by #11170

[jstarks]

This is still broken. It's working for let bindings, but not normal assignments.

E.g., this is fine:

let x = 
    unsafe { () };

This gives a false positive:

let x;
x =
    unsafe { () };

[Alexendoo]

Could you open a new issue for that @jstarks? Looks like it would have a different cause