Rust Language Expertise

Overview

Idiomatic, production-quality Rust for an engineer who already knows ownership/borrowing. This skill is decision rules, gotchas, and the traps that cost hours: async/Send correctness, error-handling architecture, serde pitfalls, and edition-2024 features. Assumes the borrow checker itself is not the problem — using it well is.

Error Handling: anyhow vs thiserror

The decision rule: will a caller ever match on the error to recover? → thiserror (concrete, matchable enum). Does the error only bubble up to be logged/reported? → anyhow (type-erased, context chains). Never put anyhow::Error in a library's public API — it erases the type and denies callers any recovery. Libraries expose thiserror enums; binaries/apps consume with anyhow.

// Library boundary: thiserror. Each variant = a distinct, matchable failure mode.
use thiserror::Error;