#[cfg(test)]
mod tests {
    use pisserror_macros::Error;
    use std::error::Error;

    /// An error type that has no variants (completely valid)
    #[derive(Debug, Error)]
    #[allow(unused)]
    #[non_exhaustive]
    enum NonexhaustiveError {
        #[error("hi")]
        Variant,
    }
}