How do I implement an async Drop in Rust?

Question

I have an async fn that returns a type, and want to implement Drop on that type that calls another async function. It's not clear how to do this, and I can't find anything in the docs. The most illuminating article I found is Asynchronous Destructors by withoutboats, but I don't really understand the reasoning, or where this feature is at.

Hexagonal

The point of the article is precisely to said that it's not currently possible. And propose a possible solution, but AFAIK it doesn't exist yet. – Shrivel

Answer 1

It's not clear how to do this, and I can't find anything in the docs

That's because it's not possible; there is no "async Drop". Drop must be synchronous.

See also:

• How do I synchronously return a value calculated in an asynchronous Future in stable Rust?

Trust

Answer 2

Since this question was originally answered, there has been movement in the repo, and there is now a (nightly-only) AsyncDrop trait that those interested in such things can use. It doesn't define an async fn you can implement (because we don't have async traits yet), but it gives you a pinned self you can fiddle with to call into your executor to do the work.

Undershirt

I guess when this is stabilized, this can be marked answer. – Hexagonal