fn calculate_column(fragment: &str) -> usize {
    match fragment.rfind('\n') {
        Some(p) => fragment.chars().count() - fragment[..p].chars().count() - 1,
        None => fragment.chars().count(),
    }
}
Given a string, calculates the 0 indexed column number of the character
*just after* the final character in the string
doc-chunks/src/developer.rs