and boy, what a rabbit hole. I found out about async_trait which resolves this by turning async methods into fn method() -> Pin<Box<dyn Future + Send + 'async_trait>>, but I thought that's what the async fn was syntax sugar for??? Then I ran into this member-only medium post claiming

Rust Async Traits: What Finally Works Now

Async functions in traits shipped. Here’s what that means for your service interfaces.

But I clicked through every rust release since 1.75.0 where impl AsyncTrait was shipped and couldn't find a mention of async. Now I'm just confused (and still using async_trait). Hence the question above...

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[–] Starfighter@discuss.tchncs.de 1 points 3 days ago* (last edited 3 days ago) (1 children)

I ran into the same issue not so long ago and at least for no_std I had to resort to using the async_trait crate. (The project is no_std but has alloc)

I can't recall the exact error so it might have been due to mixing async and non-async methods in the same trait. I would have to look at it again...

[–] BB_C@programming.dev 4 points 3 days ago

dyn compatibility of the trait itself is another matter. In this case, an async method makes a trait not dyn-compatible because of the implicit -> impl Future opaque return type, as documented here.

But OP didn't mention whether dyn is actually needed or not. For me, dyn is almost always a crutch (exceptions exist).