Trait send_future::SendFuture
source · pub trait SendFuture: Future {
// Provided method
fn send(self) -> impl Future<Output = Self::Output> + Send
where Self: Sized + Send { ... }
}Expand description
This trait is used as a workaround for compiler bug https://github.com/rust-lang/rust/issues/96865
Compilation of code calling async methods defined using impl syntax within Send async functions
may fail with hard-to-debug errors.
The following fails to compile with rustc 1.78.0:
ⓘ
trait X {
fn test<Y>(&self, x: impl AsRef<[Y]>) -> impl core::future::Future<Output = ()> + Send
where
Y: AsRef<str>;
}
fn call_test(x: impl X + Send + Sync) -> impl core::future::Future<Output = ()> + Send {
async move { x.test(["test"]).await }
}error: implementation of `AsRef` is not general enough
--> src/lib.rs:66:9
|
66 | async move { x.test(["test"]).await }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `AsRef` is not general enough
|
= note: `[&'0 str; 1]` must implement `AsRef<[&'1 str]>`, for any two lifetimes `'0` and `'1`...
= note: ...but it actually implements `AsRef<[&str]>`
The fix is to call send provided by this trait on the future before awaiting:
use send_future::SendFuture as _;
trait X {
fn test<Y>(&self, x: impl AsRef<[Y]>) -> impl core::future::Future<Output = ()> + Send
where
Y: AsRef<str>;
}
fn call_test(x: impl X + Send + Sync) -> impl core::future::Future<Output = ()> + Send {
async move { x.test(["test"]).send().await }
}