{"ast_node_type":"function","tokens":[{"end":93,"kind":"keyword","start":0,"text":"fn"}]}
    fn unescape(s: &str, mut callback: impl FnMut(Range<usize>, Result<char, EscapeError>)) {
    const RAW_PREFIX: &'static str = "br";
        unescape_byte_str(s, |range, res| callback(range, res.map(char::from)))