undocumented_unsafe_blocks can be broken by rustfmt

[clarfonthey]

Summary

Consider the following code:

// SAFETY: trust me ok
long_var_name = unsafe {
    /* ... */
};

Normally, rustfmt will either leave the unsafe block as above or convert this into the following, depending on its length:

// SAFETY: trust me ok
long_var_name = unsafe { /* ... */ };

However, in rare cases, if /* ... */ is exactly the right length, rustfmt will emit:

// SAFETY: trust me ok
long_var_name =
    unsafe { /* ... */ };

Which breaks the undocumented_unsafe_blocks lint, since the comment isn't immediately before the line with unsafe. It should accept cases like this.

Lint Name

undocumented_unsafe_blocks

[notriddle]

When I run this with a current version of clippy, the third test doesn't lint thanks to the accept-comment-above-statement option, which is turned on by default.

This feature was actually merged before this issue was opened, and made its way to stable in November 2023.