Variant

cas-result

The outcome of a swap.

variant cas-result {
  swapped,
  stale(option<entry>),
}

Cases

Case	Payload	Description
swapped	—	The new value was written.
stale	option<entry>	A precondition did not hold; nothing was written. The current entry is returned (`none` if the key is absent) so the caller can recompute and retry without a separate read.