Sure, but those are arguably more like implementation details as far as end users are concerned, aren't they? At least off the top of my head I'd imagine tokio

Sure, but those are arguably more like implementation details as far as end users are concerned, aren't they? At least off the top of my head I'd imagine tokio would require Send + Sync for tasks due to its work-stealing architecture regardless of whether it uses Wake or RawWaker/RawWakerVTable internally. I find it interesting that there's relatively recent discussion about adding LocalWaker back in [0] after it was removed [1]. Wonder what changed. [0]: https://github.com/rust-lang/libs-team/issues/191 https://github.com/rust-lang/libs-team/issues/191 [1]: https://github.com/aturon/rfcs/pull/16 https://github.com/aturon/rfcs/pull/16