async_trait_proto

使用在RFC 3185 Static Async Fn in Traits中描述的降级技术在异步特质中。

它应该比async-trait更快，因为它在每个调用和类型擦除上都不使用分配。

基准测试

需要这些功能标志和一个nightly编译器

• #![功能(generic_associated_types)]
• #![功能(type_alias_impl_trait)]

示例

#![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]
use async_trait_proto::async_trait_proto;
struct Foo;

#[async_trait_proto]
trait Bar {
    async fn wait(&self);
}

#[async_trait_proto]
impl Bar for Foo {
    async fn wait(&self) {
        sleep(Duration::from_secs(10)).await;
    }
}

Send + Sync

特质定义可以包含属性，指示生成的Future必须是Send和/或Sync。当使用tokio等工作窃取调度器时，这很重要。

#![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]
use async_trait_proto::async_trait_proto;
struct Foo;

#[async_trait_proto]
trait Bar {
    #[send]
    async fn wait(&self);
}

#[async_trait_proto]
impl Bar for Foo {
    async fn wait(&self) {
        todo!()
    }
}

// this trait can now be used with tokio::spawn
async fn spawn_trait<T: Bar + Sync + Send + 'static>(foo: T) {
    let handle = tokio::spawn(async move {
        foo.wait().await;
    });
    handle.await;
}

另一方面，这将无法编译

# #![feature(generic_associated_types)]
# #![feature(type_alias_impl_trait)]
# use async_trait_proto::async_trait_proto;
# struct Foo;

#[async_trait_proto]
trait Bar {
    async fn wait(&self);
}

# #[async_trait_proto]
# impl Bar for Foo {
#     async fn wait(&self) {
#         todo!()
#     }
# }
// this trait can not now be used with tokio::spawn
async fn spawn_trait<T: Bar + Sync + Send + 'static>(foo: T) {
    let handle = tokio::spawn(async move {
        foo.wait().await;
    });
    handle.await;
}

许可证：无许可证