Macro map_outputs 

macro_rules! map_outputs {
    ($first:pat $(, $rest:pat)* $(,)?) => { ... };
}

Destructure a left-nested output tuple from crate::MapArmStackOwned::take_outputs or crate::MapArmStack::take_outputs.

let (claim, map_outputs!(opt_secs, opt_nanos)) = hit!(map.iterate(arms).await);

Expands to the nested pattern (((), opt_secs), opt_nanos).