rust

Rust: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for rust.

Table of Contents

1. [Ownership & Borrowing](#ownership)
2. [Error Handling](#errors)
3. [Iterators](#iterators)
4. [Pattern Matching](#patterns)
5. [Structs & Enums](#structs)
6. [Concurrency](#concurrency)
7. [Anti-patterns specific to Rust](#antipatterns)

---

1. Ownership & Borrowing {#ownership}

// ❌ Cloning to avoid thinking about lifetimes
fn get_name(user: &User) -> String {
    user.name.clone()
}

// ✅ — return a reference when the data lives long enough
fn get_name(user: &User) -> &str {
    &user.name
}

// ❌ Taking ownership when borrowing suffices
fn print_name(name: String) {
    println!("{name}");
}

// ✅
fn print_name(name: &str) {
    println!("{name}");
}

// ❌ Unnecessary .to_string() / .to_owned() in hot paths
let key = id.to_string();
map.get(&key)

// ✅ — use Borrow trait; HashMap<String, V> accepts &str as key
map.get(id)

Prefer &str over String in function parameters unless the function needs to own the data.

---

2. Error Handling {#errors}

// ❌ .unwrap() in production code
let file = File::open(path).unwrap();

// ✅
let file = File::open(path)
    .map_err(|e| AppError::Io { path: path.to_owned(), source: e })?;