fn print_chain(&self, f: &mut fmt::Formatter) -> fmt::Result {

    pub(crate) fn display(&self, f: &mut fmt::Formatter) -> fmt::Result {

        let mut chain = self.chain().skip(1).enumerate().peekable();
        if let Some((n, error)) = chain.next() {
            write!(f, "\n\nCaused by:\n    ")?;
            if chain.peek().is_some() {
                write!(f, "{}: ", n)?;

        if f.alternate() {
            for cause in self.chain().skip(1) {
                write!(f, ": {}", cause)?;

            write!(f, "{}", error)?;
            for (n, error) in chain {
                write!(f, "\n    {}: {}", n, error)?;
            }

    pub(crate) fn display(&self, f: &mut fmt::Formatter) -> fmt::Result {
        if f.alternate() {
            self.print_chain(f)
        } else {
            write!(f, "{}", self.error())
        }
    }

        self.print_chain(f)?;
        writeln!(f)?;

        writeln!(f, "{}", self.error())?;
        let mut chain = self.chain().skip(1).enumerate().peekable();
        if let Some((n, error)) = chain.next() {
            write!(f, "\nCaused by:\n    ")?;
            if chain.peek().is_some() {
                write!(f, "{}: ", n)?;
            }
            writeln!(f, "{}", error)?;
            for (n, error) in chain {
                writeln!(f, "    {}: {}", n, error)?;
            }
        }

/// failed to read instrs from ./path/to/instrs.jsox
///
/// Caused by:
///     No such file or directory (os error 2)

/// failed to read instrs from ./path/to/instrs.jsox: No such file or directory (os error 2)

f failed
Caused by:
    oh no!\

f failed: oh no!\

g failed
Caused by:
    0: f failed
    1: oh no!\

g failed: f failed: oh no!\