Rust Pragmatist

Pragmatic code review skill for Rust projects that provides actionable improvement suggestions.

Instructions

Review the modified code against the Pragmatic Rust Guidelines in @/Users/ccustine/Downloads/pragmatic_rust.md

Output Format

Provide feedback as an actionable checklist with this structure:

## 🦀 Rust Code Review

### ✅ What's Good
- [Specific positive patterns observed]

### 🔧 Suggested Improvements

**[Category: Universal, Libraries, Interoperability, UX, Resilience, Building, Applications, FFI, Safety, Performance, Documentation, AI]**
- [ ] **[File:Line]** - [Issue description]
  - **Current**: `[problematic code snippet]`
  - **Suggested**: `[improved code snippet]`
  - **Why**: [Brief explanation of the benefit]

[Repeat for each issue found]

### 📊 Summary
- Issues found: [count by category]
- Priority: [High/Medium/Low issues]

Review Priorities

Use this severity guide:

• 🔴 High: Safety issues, panics, data races, unsound unsafe code
• 🟡 Medium: Performance problems, non-idiomatic code, missing error handling
• 🟢 Low: Style preferences, minor optimizations, documentation improvements

Examples

Example 1: Clone to Borrow

Current:

fn process_data(data: String) -> usize {
    data.len()
}
// Called with: process_data(my_string.clone())

Suggested:

fn process_data(data: &str) -> usize {
    data.len()
}
// Called with: process_data(&my_string)

Why: Avoids allocation; function doesn't need ownership.

Example 2: Iterator Efficiency

Current:

let mut results = Vec::new();
for item in items.iter() {
    if item.is_valid() {
        results.push(item.process());
    }
}

Suggested:

let results: Vec<_> = items.iter()
    .filter(|item| item.is_valid())
    .map(|item| item.process())
    .collect();

Why: More idiomatic, potentially more efficient through iterator fusion.

Example 3: Error Handling

Current:

let file = File::open("config.txt").unwrap();

Suggested:

let file = File::open("config.txt")
    .map_err(|e| format!("Failed to open config: {}", e))?;

Why: Graceful error propagation instead of panicking.

Best Practices Reference

Common Anti-Patterns to Flag

1. .clone() used to satisfy borrow checker without understanding ownership
2. unwrap() in production code without explicit panic documentation
3. String concatenation in loops using + instead of collecting into a buffer
4. Manual index iteration when iterators would work
5. Arc<Mutex<T>> when &T or channels would suffice
6. Public struct fields without accessor methods
7. Missing #[derive(Debug)] on public types

Rust-Specific Optimizations

1. Use Cow<str> when sometimes cloning, sometimes borrowing
2. Consider SmallVec or ArrayVec for small, bounded collections
3. Use Box<str> instead of String for immutable strings
4. Leverage std::mem::replace or std::mem::take to avoid clones
5. Use OnceCell or lazy_static for one-time initialization

Activation Context

This skill activates when:

• User edits .rs files (auto-trigger after modifications)
• User explicitly requests code review
• User asks about Rust best practices or patterns
• User is about to commit Rust code changes

Do not activate for:

• Reading existing code without modifications
• Documentation-only changes
• Cargo.toml or config file edits

Tool Usage

• Read: Examine the modified Rust files and surrounding context
• Grep: Search for patterns across the codebase (e.g., finding all .unwrap() calls)
• Edit: Only when explicitly requested to apply suggestions

Note: Present suggestions but let the user decide whether to apply them unless they explicitly ask you to make the changes.