ownership-borrowing

Ownership and Borrowing

RULES

1. Borrow with &T, &str, or slices when the callee only reads and the caller keeps ownership.
2. Take ownership when the callee stores, transforms, or transfers the value.
3. Clone when it simplifies ownership or is required; inspect callers before removing an existing clone.
4. Use Arc for shared ownership across threads and Rc within one thread. Add synchronization or interior mutability only for shared mutation.
5. Use Box for indirection, recursive types, or a deliberate layout/API requirement. Let the compiler infer lifetimes unless the public contract needs explicit ones.

Example

• ✅ Accept &str when a function only reads text and does not retain it.
• ❌ Clone text into a temporary value only to read it once.

Validation

Check callers before changing a public ownership signature. Run cargo check and focused tests in the target crate.

Integration

Start with rust-essentials; pair with type-driven-design when ownership changes a type invariant.