Can you please release a new version that includes this change?

Creating a new release is fine, but this is just a minimal version issue that can be fixed by just running cargo update without a new release.

Sorry, I don't understand. What do I tell cargo update so it grabs a version of async-executor that includes this change?

This PR just raises the minimal version requirement for slab, not the version actually used. Even without an async-executor containing this change, a cargo update on your part will increase the slab version and thus fix the problem.

But it didn't. I ran into this problem precisely after running cargo update (from a 4-year-old code base).

Sorry. I'm wrong, it popped up after cargo upgrade.

Since cargo upgrade brings direct dependencies up to the latest version and does nothing for indirect dependencies, so I think that running cargo update should bring the slab version up to date as well.

Yeah, it's all fixed. I got confused between the two commands. Thanks for explaining, and sorry for the spam.

Published in 1.13.2.