Unable to use async fn in FromRequestParts implementation

[JimitStream]

Summary

As the async traits feature has been stabilised in rust 1.75, I thought that I would not need the async_trait macro from the async_trait crate, but when I try to use async fn in a trait FromRequestParts implementation:

impl<S: Send + Sync> FromRequestParts<S> for Ctx {
	type Rejection = Error;

	async fn from_request_parts(parts: &mut Parts, _state: &S) -> Result<Self> {
		todo!()
	}
}

I get the following error, when I try to compile the provided code:
lifetime parameters or bounds on method from_request_parts do not match the trait declaration

axum version

0.7.1

[jplatte]

This is expected. Switching to native async-fn-in-trait is a breaking change in the library code that will be part of the 0.8.0 release.

[JimitStream]

Thanks for the reply, but I am still confused, if the trait definition does not include async-fn-in-trait fn definition, does it mean, that when implementing the same trait, we would not be able to implement it as async trait, and we would also have to use -> impl Future<Output = ...> or the async_trait macro?? if so, please provide a little bit information about why... because as per my knowledge, the async fn just desugars to -> impl Future<Output = ...>, so it should work... I don't know if I'm wrong...

Also can you please explain a bit about the error that I am receiving...

[jplatte]

What async_trait transforms a trait definition or implementation to is a lot different to what async-fn-in-trait (AFIT) / return-position-impl-trait-in-traits (RPITIT) is, they are just not compatible. Either both the definition and impls need to use #[async_trait], or not. For 0.8, axum's trait definitions will use RPITIT, which is compatible with AFIT in impls. For more details, see the recent rust-lang.org blog post.