rust

name	rust
description	Use when: write or review idiomatic Rust with sound ownership, error handling, and zero-cost abstractions.

Goal: safe, idiomatic Rust that the borrow checker and tests both accept.

Use for:

• new crates, modules, or performance-sensitive code
• reviewing ownership, lifetimes, and error handling
• replacing unwrap-heavy or clone-heavy code

Workflow:

1. Model data with enums and structs; make invalid states unrepresentable.
2. Return Result with a typed error; reserve panics for bugs.
3. Borrow by default; clone only with a reason.
4. Use iterators and combinators over manual index loops.
5. Encode invariants in the type system, not runtime checks.
6. Verify with cargo test, clippy, and cargo fmt.

Idioms:

• ? operator for error propagation
• Option/Result combinators (map, and_then, ok_or)
• thiserror for libraries, anyhow for applications
• traits for shared behavior; generics with bounds
• prefer &str/&[T] params over owned types

Rules:

• avoid unwrap/expect outside tests and proven invariants
• do not reach for unsafe without a documented justification
• let the borrow checker guide design, not fight it
• keep clippy clean; warnings are signal