Compile failed when tokio::sync::mpsc::Sender send format!() String

[frostRed]

Version

tokio-0.2-alpha.6

rust nightly-20191024

Platform

Manjaro Linux AMD64

Description

Compile failed when tokio::sync::mpsc::Sender send format!() String.

I am not sure if this is a compiler bug or a problem with tokio.

use tokio::sync::mpsc::{Sender, channel};
use tokio::runtime::{self};
use futures::{FutureExt, TryFutureExt, StreamExt};
use std::thread::sleep;
use std::time::Duration;

fn main() {
    let runtime = runtime::Builder::new()
        .core_threads(2)
        .name_prefix("tokio-")
        .build()
        .map_err(|e| panic!("New Runtime failed: {:?}", e))
        .expect("tokio runtime error");

    let (tx, rx) = channel::<String>(2);
    let e = runtime.executor();
    e.spawn(t(tx.clone()));

    e.spawn(async move {
        let mut rx = rx;
        while let Some(s) = rx.next().await{
            println!("{}", s);
        }
    });

    sleep(Duration::from_secs(10));
}

async fn t(tx: Sender<String>) {
    let mut t = tx.clone();
    for i in 0..5u8 {
        let s = format!("{}", i);
        t.send(s).map_err(|_| ()).map(|_| ()).await;

// can't compile
//        t.send(format!("{}", i)).map_err(|_| ()).map(|_| ()).await;
    }
}

[sinkuu]

This is a compiler bug. rust-lang/rust#64960