Macro combine_errors

macro_rules! combine_errors {
    ($result:expr) => { ... };
    ($first:expr, $second:expr $(,)?) => { ... };
    ($first:expr, $second:expr, $third:expr $(,)?) => { ... };
}

Combine multiple results into a single result by combining errors. Note we could use recursion here but the tuple would be nested. E.g. (a, (b, c)) instead of (a, b, c).