Rust Code Quality

Review skill for checking Rust code against idiomatic patterns and best practices.

Checklist

Error Handling

• Uses thiserror for library errors, anyhow for applications
• No .unwrap() or .expect() in production paths (use ? operator)
• Error types have meaningful context/payloads
• Result is returned, not panics
• Uses ? operator, not .unwrap() chains

Ownership & Borrowing

• Prefers borrowing (&T, &mut T) over cloning
• Uses Clone only when necessary
• Avoids unnecessary Arc/Rc when ownership transfer works
• Lifetime annotations are minimal and correct
• No needless to_string() / clone() in hot paths

Idiomatic Patterns

• Uses iterators over manual loops (for i in 0..len → .iter())
• Uses if let / match for Option/Result handling
• Uses ? for early returns, not nested if let
• Prefers impl Trait for return types when appropriate
• Uses builder pattern for complex construction
• Derives common traits: Debug, Clone, Default where applicable

Naming Conventions (RFC 430)

• Types: PascalCase
• Functions/methods: snake_case
• Constants: SCREAMING_SNAKE_CASE
• Conversion methods: as_* (cheap ref), to_* (expensive), into_* (ownership)
• Getters: no get_ prefix (just fn name(&self))
• Predicates: is_*, has_*, can_*

API Design

• Public items have doc comments (///)
• Examples in doc comments use ? not unwrap
• Implements standard traits: From, TryFrom, Default, Display
• Uses newtypes for type safety (not raw primitives)
• Validates inputs at boundaries
• Functions take impl Into<T> for flexible APIs

Async/Concurrency

• Uses tokio::spawn for fire-and-forget tasks
• Channels sized appropriately (not unbounded without reason)
• No blocking in async contexts (use spawn_blocking)
• Mutex guards dropped before await points
• Uses Arc for shared ownership across threads

Performance

• Avoids allocations in hot paths
• Uses &str over String for borrowed data
• Uses Cow<str> when ownership is conditional
• Prefers Vec::with_capacity when size is known
• Uses #[inline] sparingly and intentionally

Project Structure

• mod.rs or module/mod.rs pattern is consistent
• Public API is re-exported cleanly from lib.rs
• Internal modules use pub(crate) not pub
• Tests in tests/ or #[cfg(test)] modules
• Feature flags for optional dependencies

Clippy Lints

Run these checks:

cargo clippy -- -W clippy::pedantic -W clippy::nursery
cargo clippy -- -D clippy::unwrap_used -D clippy::expect_used

Key lint groups:

• clippy::correctness - Must fix (deny by default)
• clippy::suspicious - Should fix
• clippy::style - Idiomatic code
• clippy::complexity - Simplification opportunities
• clippy::perf - Performance improvements
• clippy::pedantic - Extra strictness (recommended)

Common Anti-Patterns

Wrong

// Unnecessary clone
let name = self.name.clone();
do_something(&name);

// Unwrap in production
let value = map.get("key").unwrap();

// Manual loop
for i in 0..vec.len() {
    process(vec[i]);
}

// Nested if-let
if let Some(x) = opt {
    if let Ok(y) = x.parse() {
        // ...
    }
}

// Getter with get_ prefix
fn get_name(&self) -> &str { &self.name }

Right

// Borrow directly
do_something(&self.name);

// Handle error properly
let value = map.get("key").ok_or(MyError::KeyNotFound)?;

// Iterator
for item in &vec {
    process(item);
}

// let-else or ? operator
let Some(x) = opt else { return None };
let y = x.parse()?;

// Clean getter
fn name(&self) -> &str { &self.name }

How to Use

1. Run cargo clippy -- -W clippy::pedantic first
2. Read the files to review
3. Check against patterns above
4. Report issues with file:line references
5. Suggest idiomatic fixes

References

• Rust API Guidelines
• Clippy Lints
• The Rust Book