Span joining two Flux instances together

span.rs

fn span(self, rhs: Flux) -> Self {
    let words = {
        // If the span is formed along a non-space to non-space boundary the word count is one less than the sum.
        if let (CharType::NotSpace, CharType::NotSpace) = (self.rightmost_char_type, rhs.leftmost_char_type) {
            self.words + rhs.words - 1
        } else {
            self.words + rhs.words
        }
    };
    Flux::new(self.leftmost_char_type, words, self.lines + rhs.lines, rhs.rightmost_char_type)
}