syntex_syntax::span_err_or_warn!

macro_rules! span_err_or_warn {
    ($is_warning:expr, $session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
        __diagnostic_used!($code);
        if $is_warning {
            $session.span_warn_with_code($span, &format!($($message)*), stringify!($code))
        } else {
            $session.span_err_with_code($span, &format!($($message)*), stringify!($code))
        }
    })
}