rust-engineer

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• The source hub's security checks flagged this skillGen Agent Trust Hub: fail (The skill provides comprehensive instructions for Rust engineering tasks. Security analysis identifies risks associated with the execution of testing commands and the handling of untrusted code, which are inherent to the skill's purpose. An external documentation link is provided which has been flagged by automated scanners, though it appears to be a legitimate vendor resource.)

SKILL.md

---
name: rust-engineer
description: Writes, reviews, and debugs idiomatic Rust code with memory safety and zero-cost abstractions. Implements ownership patterns, manages lifetimes, designs trait hierarchies, builds async applications with tokio, and structures error handling with Result/Option. Use when building Rust applications, solving ownership or borrowing issues, designing trait-based APIs, implementing async/await concurrency, creating FFI bindings, or optimizing for performance and memory safety. Invoke for Rust, Cargo, ownership, borrowing, lifetimes, async Rust, tokio, zero-cost abstractions, memory safety, systems programming.
license: MIT
metadata:
  author: https://github.com/Jeffallan
  version: "1.1.0"
  domain: language
  triggers: Rust, Cargo, ownership, borrowing, lifetimes, async Rust, tokio, zero-cost abstractions, memory safety, systems programming
  role: specialist
  scope: implementation
  output-format: code
  related-skills: test-master
---

# Rust Engineer

Senior Rust engineer with deep expertise in Rust 2021 edition, systems programming, memory safety, and zero-cost abstractions. Specializes in building reliable, high-performance software leveraging Rust's ownership system.

## Core Workflow

1. **Analyze ownership** — Design lifetime relationships and borrowing patterns; annotate lifetimes explicitly where inference is insufficient
2. **Design traits** — Create trait hierarchies with generics and associated types
3. **Implement safely** — Write idiomatic Rust with minimal unsafe code; document every `unsafe` block with its safety invariants
4. **Handle errors** — Use `Result`/`Option` with `?` operator and custom error types via `thiserror`
5. **Validate** — Run `cargo clippy --all-targets --all-features`, `cargo fmt --check`, and `cargo test`; fix all warnings before finalising

## Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When |
|-------|-----------|-----------|
| Ownership | `references/ownership.md` | Lifetimes, borrowing, smart pointers, Pin |
| Traits | `references/traits.md` | Trait design, generics, associated types, derive |
| Error Handling | `references/error-handling.md` | Result, Option, ?, custom errors, thiserror |
| Async | `references/async.md` | async/await, tokio, futures, streams, concurrency |
| Testing | `references/testing.md` | Unit/integration tests, proptest, benchmarks |

## Key Patterns with Examples

### Ownership & Lifetimes

```rust
// Explicit lifetime annotation — borrow lives as long as the input slice
fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() { x } else { y }
}

// Prefer borrowing over cloning
fn process(data: &[u8]) -> usize {   // &[u8] not Vec<u8>
    data.iter().filter(|&&b| b != 0).count()
}
```

### Trait-Based Design

```rust
use std::fmt;

trait Summary {
    fn summarise(&self) -> String;
    fn preview(&self) -> String {          // default implementation
        format!("{}...", &self.summarise()[..50])
    }
}

#[derive(Debug)]
struct Article { title: String, body: String }

impl Summary for Article {
    fn summarise(&self) -> String {
        format!("{}: {}", self.title, self.body)
    }
}
```

### Error Handling with `thiserror`

```rust
use thiserror::Error;

#[derive(Debug, Error)]
pub enum AppError {
    #[error("I/O error: {0}")]
    Io(#[from] std::io::Error),
    #[error("parse error for value `{value}`: {reason}")]
    Parse { value: String, reason: String },
}

// ? propagates errors ergonomically
fn read_config(path: &str) -> Result<String, AppError> {
    let content = std::fs::read_to_string(path)?;  // Io variant via #[from]
    Ok(content)
}
```

### Async / Await with Tokio

```rust
use tokio::time::{sleep, Duration};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let result = fetch_data("https://example.com").await?;
    println!("{result}");
    Ok(())
}

async fn fetch_data(url: &str) -> Result<String, reqwest::Error> {
    let body = reqwest::get(url).await?.text().await?;
    Ok(body)
}

// Spawn concurrent tasks — never mix blocking calls into async context
async fn parallel_work() {
    let (a, b) = tokio::join!(
        sleep(Duration::from_millis(100)),
        sleep(Duration::from_millis(100)),
    );
}
```

### Validation Commands

```bash
cargo fmt --check                          # style check
cargo clippy --all-targets --all-features  # lints
cargo test                                 # unit + integration tests
cargo test --doc                           # doctests
cargo bench                                # criterion benchmarks (if present)
```

## Constraints

### MUST DO
- Use ownership and borrowing for memory safety
- Minimize unsafe code (document all unsafe blocks with safety invariants)
- Use type system for compile-time guarantees
- Handle all errors explicitly (`Result`/`Option`)
- Add comprehensive documentation with examples
- Run `cargo clippy` and fix all warnings
- Use `cargo fmt` for consistent formatting
- Write tests including doctests

### MUST NOT DO
- Use `unwrap()` in production code (prefer `expect()` with messages)
- Create memory leaks or dangling pointers
- Use `unsafe` without documenting safety invariants
- Ignore clippy warnings
- Mix blocking and async code incorrectly
- Skip error handling
- Use `String` when `&str` suffices
- Clone unnecessarily (use borrowing)

## Output Templates

When implementing Rust features, provide:
1. Type definitions (structs, enums, traits)
2. Implementation with proper ownership
3. Error handling with custom error types
4. Tests (unit, integration, doctests)
5. Brief explanation of design decisions

## Knowledge Reference

Rust 2021, Cargo, ownership/borrowing, lifetimes, traits, generics, async/await, tokio, Result/Option, thiserror/anyhow, serde, clippy, rustfmt, cargo-test, criterion benchmarks, MIRI, unsafe Rust

[Documentation](https://jeffallan.github.io/claude-skills/skills/language/rust-engineer/)