# Expert Rust Skill > Instructions, patterns, and best practices for writing idiomatic, high-performance, and safe Rust code. Use when this capability is needed. - Skill: `tomevault-io/expert-rust-skill` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/expert-rust-skill` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/expert-rust-skill/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/expert-rust-skill --- # Expert Rust Skill This skill serves as a guide for writing production-grade Rust code, focusing on safety, concurrency, and idiomatic patterns. ## 1. Ownership & Memory Management - **Borrowing**: Prefer borrowing (`&T`, `&mut T`) over taking ownership when data doesn't need to be consumed. - **Cloning**: Be explicit with `.clone()`. Avoid it in hot paths unless necessary. Use `Arc` for shared ownership across threads/tasks. - **Lifetimes**: Explicitly strictly define lifetimes `'a` only when the compiler cannot infer them. ## 2. Error Handling - **Result & Option**: Never use `.unwrap()` or `.expect()` in production code unless you have proof that it will never panic (and comment that proof). - **Propagation**: Use the `?` operator to propagate errors. - **Crates**: - Use `thiserror` for library error definitions (enum implementation). - Use `anyhow` for application-level error handling and context (`.context("...")`). ## 3. Concurrency & Async - **Runtime**: Use `tokio` for async operations. - **Send & Sync**: Ensure types passed across thread/task boundaries implement `Send` (and `Sync` if shared). - **Blocking**: NEVER block the async runtime thread. Use `tokio::task::spawn_blocking` for CPU-intensive or synchronous I/O operations. - **Synchronization**: Use `tokio::sync::Mutex` for async critical sections, but prefer message passing (`tokio::sync::mpsc`) via channels over shared state where possible. ## 4. Type System & Traits - **Newtypes**: Use the "Newtype" pattern (`struct ID(String)`) to enforce type safety and avoid primitives obsession. - **Traits**: Prefer defining behavior via Traits. Use `impl Trait` for return types to reduce signature complexity. - **Generics**: Use Generics with trait bounds (`T: AsRef`) to increase API flexibility. ## 5. Idiomatic Rust - **Clippy**: Always respect `cargo clippy`. Treat warnings as errors. - **Formatting**: Run `cargo fmt` automatically. - **Iterators**: Prefer functional iterator chains (`.map()`, `.filter()`, `.collect()`) over raw `for` loops for readability and potential compiler optimizations. - **Pattern Matching**: Use `match` with exhaustive patterns. Use `if let` for single pattern handling. ## 6. Testing - **Unit Tests**: Place unit tests in the same file `mod tests { ... }`. - **Integration Tests**: Place integration tests in `tests/` directory. - **Doc Tests**: Write examples in documentation comments (`///`) which serve as tests. ## 7. Performance - **Allocations**: Minimize heap allocations. Use `&str` instead of `String` when possible. - **Data Structures**: Choose the right container (e.g., `HashMap`, `BTreeMap`, `Vec`) based on access patterns. - **Buffering**: Use `BufReader`/`BufWriter` for I/O operations to reduce syscalls. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/basilgregory) — claim your Tome and manage your conversions.