Function unescape_unicode

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

Takes the contents of a unicode-only (non-mixed-utf8) literal (without quotes) and produces a sequence of escaped characters or errors.

Values are returned by invoking callback. For Char and Byte modes, the callback will be called exactly once.