rust-ownership

E0382 (use of moved value) is usually fixed by borrowing with & instead of moving, or reordering so the move is the last use. E0499 (two mutable borrows) is fixed by shortening one borrow's scope via non-lexical lifetimes or splitting into disjoint fields.

Use Box for heap allocation, recursive types, or trait objects; Rc for multiple owners on one thread; RefCell for mutation through a shared reference; and Rc<RefCell<T>> for shared mutable data. Cow fits returns that are usually borrowed but occasionally owned.

Take &T when you only read the value, &mut T when you mutate it in place and the caller keeps it, and T when you store, consume, or move it into a thread or struct. Default to borrowing inputs and owning only when necessary.

Error E0597 means a reference outlives the value it points to. Fix it by extending the owner's scope, hoisting the owner above the borrow, or storing the owned value instead of the reference in structs.

Use std::sync::LazyLock for a lazily computed static, or OnceLock with get_or_init for a struct field initialized on first use. Both are thread-safe and replace the older lazy_static crate since Rust 1.80.

Cloning is appropriate for small Copy-like data, breaking self-referential tangles, or handing owned data to a thread. It is wrong when it merely hides a borrow that would have worked, which usually signals a design issue.