Can't use ? if try_stream! wraps select!

[stusmall]

I have multiple streams I am joining in a select along with a timeout future that caused me to run into this. I tried to boil it down to a minimal code sample that can trigger the problem. It as follows:

use std::io;
use std::future::Future;
use socket2::{Socket, Domain, Type, Protocol};
use futures::Stream;
use async_stream::try_stream;
use futures::select;
use tokio::time::sleep;
use std::time::Duration;
use futures::FutureExt;
use futures::StreamExt;

fn await_results(
    mut stream1: impl Stream<Item = io::Result<i32>> + Unpin,
) -> impl Stream<Item = io::Result<i32>> {
    try_stream! {
        let mut stream1_future = stream1.next().fuse();
        select!{
            result = stream1_future => {
                stream1_future = stream1.next().fuse();
                match result {
                    Some(x) => {
                        let y = x?;
                        yield y;
                    }
                    None => {

                    }
                }
            }
        }
    }
}


#[tokio::main]
async fn main() -> io::Result<()> {
    Ok(())
}

This fails with the error:

error[E0277]: the `?` operator can only be used in an async block that returns `Result` or `Option` (or another type that implements `Try`)
  --> src/main.rs:22:33
   |
15 | /     try_stream! {
16 | |         let mut stream1_future = stream1.next().fuse();
17 | |         select!{
18 | |             result = stream1_future => {
...  |
22 | |                         let y = x?;
   | |                                 ^^ cannot use the `?` operator in an async block that returns `()`
...  |
30 | |         }
31 | |     }
   | |_____- this function should return `Result` or `Option` to accept `?`
   |
   = help: the trait `Try` is not implemented for `()`
   = note: required by `from_error`

And I confirmed I'm on 0.3.2 so I have the fix for #27

[stusmall]

I'm able to easily work around this by using stream! rather than try_stream. So far it looks like I can still get my job done just without the niceness of ?

[taiki-e]

This seems due to that visit_token_stream_impl only visits yield but not ?.

https://github.com/tokio-rs/async-stream/blob/8bf33a6d2cf00257a9235a14ae264aa5c74380ba/async-stream-impl/src/lib.rs#L45-L94

[ashtuchkin]

Just bumped into this. I'm using latest v0.3.5.