Macro std::result::yield_try

macro yield_try($res) { ... }

source

Extract the success value or yield the calling coroutine.

This is similar to try, but usable in coroutine functions that yield Result values.

Expands to the following expression 

if $.is_ok() {
    $.unwrap()
} else {
    yield Result::err(self.unwrap_err())
    return
}