特征“futures：：Stream”没有为我的类型实现

问：

我正在创建一个更新系统。它在 2 个二进制文件之间创建补丁，压缩补丁和二进制文件并启动 Web 服务器。

我需要从闭包调用异步 fn。 所以闭包需要异步才能使用 fnawait

我愿意

let repair_stream = future::lazy(move |_| async {
        let mut failures = {
            let state = &mut *shared_state_r.borrow_mut();
            state.previous_failures = mem::take(&mut state.failures);
            state.previous_failures.clone()
        };
        if !failures.is_empty() {
            failures.sort();
            global_progression_r.lock().await.stage = UpdateStage::FindingRepairPath; // note the use of await
            Either::Left(
                update_internal(
                    update_options_r,
                    file_manager_r,
                    global_progression_r,
                    State::New, //< force to repair from no starting revision
                    shared_state_r,
                    repository,
                    goal_version_r,
                    UpdateFilter { failures },
                    UpdateStage::Repairing,
                )
                .try_flatten_stream(),
            )
        } else {
            // nothing to repair, everything went well
            Either::Right(stream::empty())
        }
    })
    .flatten_stream();

但是得到

error[E0277]: the trait bound `impl futures::Future<Output = futures::future::Either<TryFlattenStream<impl futures::Future<Output = std::result::Result<impl futures::Stream<Item = std::result::Result<SharedUpdateProgress, UpdateError>> + '_, UpdateError>>>, futures::stream::Empty<_>>>: futures::Stream` is not satisfied
   --> lib/src/workspace/updater.rs:342:25
    |
342 |       let repair_stream = future::lazy(move |_| async {
    |  _________________________^
343 | |         let mut failures = {
344 | |             let state = &mut *shared_state_r.borrow_mut();
345 | |             state.previous_failures = mem::take(&mut state.failures);
...   |
368 | |         }
369 | |     })
    | |______^ the trait `futures::Stream` is not implemented for `impl futures::Future<Output = futures::future::Either<TryFlattenStream<impl futures::Future<Output = std::result::Result<impl futures::Stream<Item = std::result::Result<SharedUpdateProgress, UpdateError>> + '_, UpdateError>>>, futures::stream::Empty<_>>>`
370 |       .flatten_stream();
    |        -------------- required by a bound introduced by this call
    |
    = help: the following other types implement trait `futures::Stream`:
              &mut S
              Abortable<St>
              ApplyStream
              AssertUnwindSafe<S>
              Box<S>
              Buffer<S, Item>
              BufferUnordered<St>
              Buffered<St>
            and 84 others
note: required by a bound in `flatten_stream`
   --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.25/src/future/future/mod.rs:343:23
    |
343 |         Self::Output: Stream,
    |                       ^^^^^^ required by this bound in `flatten_stream`

锁定 fn 返回tokio::sync::MutexGuard

完整来源： https://github.com/Ludea/speedupdate-rs/blob/master/lib/src/workspace/updater.rs#L342

我不明白这个问题，也不知道如何解决它