# Rust Ownership Borrowing

> Use when understanding Rust ownership and borrowing.

- Skill: `loopyluci/rust-ownership-borrowing` (Agent Skill)
- Install (CLI): `npx skillmds@latest add loopyluci/rust-ownership-borrowing`
- Raw SKILL.md: https://api.skillmd.com/api/skills/loopyluci/rust-ownership-borrowing/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: MIT
- Author: LoopyLuci (https://skillmd.com/u/loopyluci)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/loopyluci/rust-ownership-borrowing

---


# Rust Ownership and Borrowing

Understanding Rust's ownership and borrowing system — from owners and references through lifetimes, borrowing rules, and common patterns.

## When to Use

- Learning Rust's ownership model
- Writing safe Rust without fighting the borrow checker
- Managing lifetimes in complex data structures
- Implementing safe abstractions

## Ownership Patterns

```rust
// Ownership transfer
fn take_ownership(s: String) -> usize { s.len() }

// Borrowing
fn borrow(s: &String) -> usize { s.len() }

// Mutable borrow
fn append(s: &mut String, text: &str) { s.push_str(text); }

// Lifetime annotations
struct Config<'a> {
    name: &'a str,
    version: &'a str,
}

impl<'a> Config<'a> {
    fn new(name: &'a str, version: &'a str) -> Self {
        Config { name, version }
    }
}

// Lifetime elision rules
fn first_word(s: &str) -> &str {
    s.split_whitespace().next().unwrap_or(s)
}
```

## Verification Checklist

- [ ] Each value has exactly one owner
- [ ] References never outlive borrowed data
- [ ] Mutable references are exclusive (no aliasing)
- [ ] Lifetime annotations only where needed (elision rules)
- [ ] Interior mutability (RefCell, Mutex) for shared mutation
- [ ] Clone vs Copy semantics understood