impl Decoration {
    /// Parses a [`Decoration`] at the beginning of the string,
    /// returning it and the remainder of the input.
    ///
    /// This operation always succeeds as it can always parse an
    /// empty decoration at the beginning.
    ///
    /// # Examples
    ///
    /// ```
    /// let word = "*#feris";
    /// let (decoration, remainder) = Decoration::parse(word);
    /// assert_eq!(decoration.premarker, PreMarker::Carþ);
    /// assert!(decoration.has_nef);
    /// assert!(!decoration.has_sen);
    /// assert_eq!(remainder, "feris");
    /// ```
    pub fn parse(s: &str) -> (Decoration, &str) {
        let mut s = s.chars().peekable();
        let has_nef = s.next_if_eq(&'*').is_some();
        let premarker_char = s.next_if(|c| "#+×@".contains(*c));
        let premarker = match premarker_char {
            Some('#') => PreMarker::Carþ,
            Some('+') => match s.next_if_eq(&'*') {
                Some(_) => PreMarker::Njor,
                None => PreMarker::Tor,
            },
            Some('×') => PreMarker::Njor,
            Some('@') => PreMarker::Es,
            _ => PreMarker::None,
        };
        let has_sen = s.next_if_eq(&'&').is_some();
        (
            Decoration {
                premarker,
                has_nef,
                has_sen,
            },
            // ERROR: no method named `as_str` found for struct `Peekable` in the current scope
            // method not found in `Peekable<Chars<'_>>`
            s.as_str(),
        )
    }
}