serialize_identifier() appears to be appending whitespace after \9

[snshn]

I encountered something interesting, thanks to a little-known hack that IE[7-9] uses.

Here's my snippet:

pub fn format_ident(ident: &str) -> String {
    let mut res: String = String::new();
    let _ = serialize_identifier(ident, &mut res);
    res = res.trim_end().to_string(); // <-- Had to add this line
    res
}

Appears to be that passing value \9 via Token::Ident to that function results in serialize_identifier() writing \9 rather than \9, hence it was breaking the original CSS hack. The test query I used is this one: div#p>svg>foreignObject>section:not(\9) and pushing that through the serialize_identifier without trim_end() was resulting in div#p>svg>foreignObject>section:not(\9 ) and hence was breaking that IE hack. I couldn't find where my code was adding extra space at the end for tabs, hence went with right-trimming it for now.

[snshn]

It looks like the optional space after the identifier can be trimmed without it breaking the desired behavior, while it makes the IE hack work. I'm gonna go ahead close this issue.