m03-mutability

To fix Rust borrow checker errors like E0596, E0499, and E0502, analyze the ownership and mutability context to decide between using exclusive mutable borrows, interior mutability, or synchronization primitives.

Choose RefCell for interior mutability in single-threaded contexts and Mutex or RwLock for shared state in multithreaded contexts, basing the decision on thread safety requirements and whether the type is Copy.

The best way to resolve a mutable borrow conflict is to evaluate whether to restructure data ownership, apply interior mutability with Cell or RefCell, or introduce locking mechanisms based on the concurrency context.

Borrowing a non-Copy type as mutable fails because Rust enforces exclusive ownership; you must either clone the value, restructure the ownership domain, or utilize interior mutability to allow controlled modification.

You need atomics for simple Copy types or Mutex and RwLock for complex non-Copy types to safely handle shared state and synchronization in async or multithreaded Rust environments.

Interior mutability works by shifting borrow checking from compile time to runtime using RefCell or to synchronization primitives like Mutex, allowing mutable access through shared references when exclusive &mut borrows are impossible.