futures_core/task/poll.rs
/// Extracts the successful type of a `Poll<T>`.
///
/// This macro bakes in propagation of `Pending` signals by returning early.
#[macro_export]
macro_rules! ready {
($e:expr $(,)?) => {
match $e {
$crate::task::Poll::Ready(t) => t,
$crate::task::Poll::Pending => return $crate::task::Poll::Pending,
}
};
}