E0594 rust type_error ai_generated true

error[E0594]: cannot assign to data in an `Arc`

ID: rust/e0594-cannot-assign-to-data-in-an-arc

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90%Fix Rate
88%Confidence
1Evidence
2023-01-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.65.0 active — — —
1.68.0 active — — —
1.72.0 active — — —

Root Cause

Attempting to mutate data behind an `Arc<T>` without interior mutability (e.g., `Mutex`, `RwLock`, or `Cell`).

generic

中文

尝试在没有内部可变性（例如 `Mutex`、`RwLock` 或 `Cell`）的情况下修改 `Arc<T>` 背后的数据。

Official Documentation

https://doc.rust-lang.org/error_codes/E0594.html

Workarounds

  1. 92% success Use `Arc<Mutex<T>>` and lock before mutation: `*arc.lock().unwrap() = new_value;` 
    Use `Arc<Mutex<T>>` and lock before mutation: `*arc.lock().unwrap() = new_value;`
  2. 95% success Use `Arc<AtomicU32>` for simple numeric types and `store` method. 
    Use `Arc<AtomicU32>` for simple numeric types and `store` method.

中文步骤

  1. 使用 `Arc<Mutex<T>>` 并在修改前加锁：`*arc.lock().unwrap() = new_value;`
  2. 对于简单的数值类型使用 `Arc<AtomicU32>` 和 `store` 方法。

Dead Ends

Common approaches that don't work:

  1. Using `unsafe` to cast `Arc<T>` to a mutable reference via raw pointer 95% fail

    Undefined behavior due to data races; violates Rust's safety guarantees.

  2. Wrapping the entire `Arc` in a `RefCell` without thread safety 70% fail

    `RefCell` is not `Sync`, so the `Arc<RefCell<T>>` cannot be shared across threads.