Adding an attribute to an unsafe block changes its formatting

[tgross35]

This is the rustfmt result for an unsafe block:

fn main() {
    // #[cfg(not(fake_flag))]
    unsafe { println!() };
}

But uncomment the attribute, and it reformats it as:

fn main() {
    #[cfg(not(fake_flag))]
    unsafe {
        println!()
    };
}

Changing the attribute probably should not change the formatting.

rustfmt 1.7.0-nightly (5119208f 2024-03-02)

[ytmimi]

A similar issue has popped up in other cases too. #5901 and #5662 immediately come to mind, but there might be others in the backlog.

I haven't looked into this, but my hunch is that rustfmt considers the newline between the attribute and the block as an indication that the block can't be written on one line.

[ytmimi]

I'm assuming this affects all blocks, not just unsafe blocks? What about async blocks for example?

[tgross35]

Good call, looks like async and probably others are the same

fn main() {
    // #[cfg(not(fake_flag))]
    async { println!() };
}

fn main() {
    #[cfg(not(fake_flag))]
    async {
        println!()
    };
}

Probably indeed the same issue as #5662 so close this if you see fit. I just noticed because the diff for rust-lang/rust#121894 looked kind of funny :)

[ytmimi]

I think its the same underlying problem as #5662, but it's occurring in a different parts of the codebase. rustfmt rewrites attrs before rewriting the AST node those attrs are associated with so I think this is a distinct issue to the others I linked.