Programming Tutorials

  If you are building complex asynchronous applications with Rust and WebAssembly, you have likely encountered this runtime panic: Uncaught Error: Recursive use of an object detected which would lead to unsafe aliasing in rust This error is arguably the most notorious hurdle in the  wasm-bindgen  ecosystem. It halts execution immediately, often occurs in edge-case race conditions, and stems from a fundamental mismatch between Rust's compile-time ownership model and JavaScript's run-to-completion event loop. This post dissects the memory model triggering this panic and provides the architectural pattern required to solve it reliably. The Root Cause: The Wasm-Bindgen Borrow Guard To understand the panic, you must understand how  wasm-bindgen  bridges the gap between the JS heap and the Rust linear memory. When you define a Rust struct with  #[wasm_bindgen] , the generated glue code wraps the raw Rust pointer. To enforce Rust's borrowing rules (specifically: m...

  If you are working with Tokio and async Rust, you have likely encountered this compiler error. It usually looks like a wall of text ending with   note: required by 'tokio::spawn' , but the core message is specific: error[E0277]: `Rc<...>` cannot be sent between threads safely // OR error[E0277]: `std::sync::MutexGuard<'_, ...>` cannot be sent between threads safely This error prevents you from spawning tasks onto the Tokio runtime. It is not a syntax error; it is a fundamental architectural constraint of work-stealing runtimes enforced by Rust's type system. The Root Cause: Async State Machines and the  Send  Trait To understand the fix, you must understand what the compiler does with an  async  block. When you write an  async  block, the Rust compiler transforms your code into a  State Machine . This state machine is implemented as an  enum  where every  .await  point represents a variant transition. Crucial...