Trait wrpc_transport::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 }
}

Provided Methods§

source

fn send(self) -> impl Future<Output = Self::Output> + Send
where Self: Sized + Send,

Implementors§

source§

impl<T> SendFuture for T
where T: Future,