wrong line length calculation

[Dushistov]

If I run:

$ rustfmt --version
0.8.3 ()

with such code:

fn test() -> Result<i32, String> {
    let r: Result<i32, String> = Ok(17);
    r.map_err(|err| format!("Someting really, really wrong, may be flash in the sun  : {}", err))?;
    Ok(15)
}

rustfmt works without problem, but if I place the same amount of chars (not bytes) into line:

fn test() -> Result<i32, String> {
    let r: Result<i32, String> = Ok(17);
    r.map_err(|err| format!("Что-то пошло совсем не так, может быть вспышка на солнце: {}", err))?;
    Ok(15)
}

it reports error: line exceeded maximum length (maximum: 100, found: 144) (sorry)

rustfmt should work with chars, not bytes, because of editors/code review tools and so on,
display both code examples using the same amount of horizontal space.

[stanislav-tkach]

I have run into this problem too and it's quite annoying.

[nrc]

dup of #6 (sorry, this is really important to fix and it has taken forever)