            }
            // single or double quotes
            Some('"') | Some('\'') => {
                pos += 1;
                let token_start = pos;
                let mut ch1 = iter.next();
                loop {
                    match ch1 {
                        Some(ch2) => {
                            pos += 1;
                            ch1 = iter.next();
                            if ch2 == ch.unwrap() {