E0277 rust type_error ai_generated true

error[E0277]: `std::rc::Rc<()>` cannot be sent between threads safely `Rc<()>` is not `Send` because `Rc` is not `Send`

ID: rust/e0277-async-fn-not-send

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90%Fix Rate
85%Confidence
1Evidence
2023-08-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
rustc 1.75 active — — —
tokio 1.35 active — — —

Root Cause

Using `Rc` inside an async block or future that is expected to implement `Send`, typically when spawning a task with `tokio::spawn`.

generic

中文

在需要实现 `Send` 的异步块或 future 中使用了 `Rc`，通常在使用 `tokio::spawn` 生成任务时发生。

Official Documentation

https://doc.rust-lang.org/stable/error_codes/E0277.html

Workarounds

  1. 95% success Replace `Rc` with `Arc` (atomic reference counting) and `RefCell` with `Mutex` or `RwLock`. 
    Replace `Rc` with `Arc` (atomic reference counting) and `RefCell` with `Mutex` or `RwLock`.
  2. 85% success Use `tokio::task::LocalSet` to spawn non-Send futures on the current thread if you must keep `Rc`. 
    Use `tokio::task::LocalSet` to spawn non-Send futures on the current thread if you must keep `Rc`.

中文步骤

  1. 将 `Rc` 替换为 `Arc`（原子引用计数），并将 `RefCell` 替换为 `Mutex` 或 `RwLock`。
  2. 使用 `tokio::task::LocalSet` 在当前线程上生成非 Send 的 future，如果你必须保留 `Rc`。

Dead Ends

Common approaches that don't work:

  1. 75% fail

    `Mutex<Rc>` still doesn't make `Rc` `Send`; `Rc` is fundamentally not thread-safe. You need `Arc` instead.

  2. 90% fail

    Unsafe to implement `Send` for `Rc`; leads to data races and undefined behavior.