Function rustc_lexer::unescape::unescape_raw_str_or_byte_str

fn unescape_raw_str_or_byte_str<F>(
    literal_text: &str, 
    mode: Mode, 
    callback: &mut F
) where
    F: FnMut(Range<usize>, Result<char, EscapeError>), 

Takes a contents of a string literal (without quotes) and produces a sequence of characters or errors. NOTE: Raw strings do not perform any explicit character escaping, here we only translate CRLF to LF and produce errors on bare CR.