Rust: What is the difference between Poll::Ready and Poll::Pending?

Poll::Ready — future complete. Poll::Pending — future not ready.

Poll::Ready:

• Future resolved.
• Value available.
• Done.

Poll::Pending:

• Future not ready.
• Waker registered.
• Re-poll later.

1use std::task::Poll;
2
3fn my_poll() -> Poll<i32> {
4    Poll::Ready(42)  // Done
5}
6
7fn my_pending() -> Poll<i32> {
8    Poll::Pending  // Not ready
9}

Key: Ready for completion, Pending for waiting.