Attribute Macro async_trait 

#[async_trait]

The #[async_trait] macro is used to desugar async functions in traits to return impl Future.

This macro is required mainly to get around the current limitation of async functions in traits, which would produce a lint warning for async_fn_in_trait if bare async functions are defined in a trait.

Example

Given the following trait definition:

#[async_trait]
pub trait CanRun {
    async fn run(&self);
}

The macro would desugar it to the following:

pub trait CanRun {
    fn run(&self) -> impl Future<Output = ()>;
}