Neo Rust Expert

Write safe, maintainable, and idiomatic Rust code by strictly following the official design patterns, leveraging Rust's powerful type system, and avoiding anti-patterns.

Gotchas

• Gotcha 1 (Async Mutex Deadlock / Send Error):

In an async function, using the standard library's std::sync::Mutex and holding its MutexGuard across an .await boundary will cause a compiler error because MutexGuard does not implement Send and cannot be transferred across threads.

• Solution: Use a local block {} to limit the MutexGuard lifetime before the .await, or use tokio::sync::Mutex instead.
• Gotcha 2 (Excessive Cloning):

To satisfy the Borrow Checker, beginners often call .clone() excessively, which introduces significant memory allocation and copy overhead.

• Solution: Prioritize passing borrowed references (e.g., &str instead of String, &[T] instead of Vec<T>), or refactor ownership structures and lifetimes.
• Gotcha 3 (Unsafe Unwrapping):

Using .unwrap() or panic!() directly in library or production-grade code will cause the application to crash, violating Rust's safety-first principle.

• Solution: Always return Result<T, E> or Option<T> for graceful error propagation, and use the ? operator or match expression to handle them.

Workflow Checklist

Progress:

• [ ] Step 1: Perceive & Inventory (Check if Cargo.toml and .rs files exist in the project, and clarify whether the task is "feature development", "refactoring", or "Code Review").
• [ ] Step 2: Load Reference (Based on the task type, dynamically load corresponding reference files: load reference/patterns.md and reference/coding-style.md for writing new code, and load reference/anti-patterns.md for reviews and debugging).
• [ ] Step 3: Implement & Validate (After writing or modifying code, compile and analyze it locally using cargo check and cargo clippy. Fix any warnings or errors until compilation passes cleanly without warnings).
• [ ] Step 4: Format & Finalize (Run cargo fmt to format the code according to official guidelines, and present output using the Output Templates).

Detailed Guidelines

Step 1 — Parse & Inventory

1. Inspect the current directory to verify if Cargo.toml exists.
2. Analyze the task. For Code Review tasks, read existing changes; for feature development, determine the target modules to create or modify.

Step 2 — Dynamic Reference Loading

To save context space, only this SKILL.md is loaded initially. Once executing the task, the Agent must load the following resources:

• Development & Architecture: Load patterns.md and coding-style.md.
• Review, Refactoring & Debugging: Load anti-patterns.md.

Step 3 — Compile & Clippy Validation Loop

Verify newly written or modified Rust code to ensure it is 100% compilable:

1. Run cargo check to verify syntax and type checking.
2. Run cargo clippy --all-targets -- -D warnings to perform strict static analysis and catch potential code smells.
3. If validation fails:

• Carefully inspect the stderr compiler errors or Clippy suggestions.
• Modify the corresponding code.
• Re-run validation until it passes cleanly.

Output Templates

Present your output using the following structured templates depending on the task type.

Template A: Code Review Report

# Rust Code Review Report

## 1. Executive Summary
*   **Score**: [1-10 rating]
*   **Summary**: [Overall feedback on code quality, ownership usage, and error handling]

## 2. Findings
> [!IMPORTANT]
> Order findings by severity (Error > Warning > Info).

*   **[Severity] Location: `src/main.rs:L12` - [Finding Title]**
    *   **Description**: [Why is this an issue? Which Rust best practice is violated?]
    *   **Recommendation**:

// Idiomatic Rust example demonstrating the fix

## 3. Top 3 Recommendations
1.  [First actionable improvement]
2.  [Second actionable improvement]
3.  [Third actionable improvement]

Template B: Implementation & Refactoring Summary

# Rust Implementation / Refactoring Summary

## 1. Overview of Changes
[Briefly summarize what Rust modules, structs, or traits were added or refactored]

## 2. Applied Design Patterns & Best Practices
*   [e.g., Applied the Typestate Pattern to ensure state safety]
*   [e.g., Replaced `.clone()` with `&str` for performance gains]

## 3. Local Verification Results
- [x] `cargo check` passed
- [x] `cargo clippy` passed with zero warnings
- [x] `cargo fmt` completed successfully

## 4. Next Steps
1.  [Recommended next action, e.g., run cargo test]
2.  [Other relevant suggestions]