Rustfmt: Needs two passes to correctly format.

[iago-lito]

I'm not sure whether this is expected behaviour or not, but the following code:

fn main() {
    for _ in 0..1 {
        ;
    }
}

Is first reformatted as

fn main() {
    for _ in 0..1 {
    }
}

And only then as

fn main() {
    for _ in 0..1 {}
}

If I need to run rustfmt twice in this case, how am I sure that I have run it enough times in other cases? Do I need to repeat every rustfmt until the file is stable?

[calebcartwright]

Thanks @iago-lito - that's a bug (at least IMO)

[topecongiro]

Here the single ; is treated as an empty statement, and in the first run, rustfmt misunderstands that the for block is not empty. In the second run, since the single ; gets removed and the block is empty, rustfmt squashes the block into a single line.

To fix this, we should filter out the empty statements from the block when checking its emptiness.