Rust Code Quality Gate

Use this skill on every Rust code change to enforce quality rules that cargo clippy does not catch.

Quick Start

1. Identify changed .rs files.
2. Run automated checks on changed files.
3. Run manual review checklist on the diff.
4. Report findings; block merge if P0/P1 issues exist.

Automated Checks

Run these on every changed .rs file (excluding test modules):

# 1. unwrap/expect in production code
rg -n '\.unwrap\(\)|\.expect\(' <changed-files> | grep -v '#\[cfg(test)\]' | grep -v 'test' | grep -v 'bench'

# 2. Silent type truncation via `as` cast
rg -n ' as (u8|u16|u32|u64|usize|i8|i16|i32|i64|isize)\b' <changed-files>

# 3. String as error type
rg -n 'Result<.*String>' <changed-files> | grep -v test

# 4. Box<dyn Error> in public APIs
rg -n 'Box<dyn.*Error' <changed-files> | grep -v test

# 5. println/eprintln in production
rg -n 'println!\|eprintln!' <changed-files> | grep -v test

# 6. Ordering::Relaxed usage (verify each is intentional)
rg -n 'Ordering::Relaxed' <changed-files>

Manual Review Checklist

For every Rust code change, verify:

Error Handling

• No unwrap() or expect() in production code without justification comment
• No Result<_, String> in public API signatures
• No Box<dyn Error> in public trait/struct methods
• Error::source() is overridden when inner error is stored
• Error messages are actionable (what failed, with what input)

Type Safety

• No silent as truncation (negative→unsigned, large→small)
• try_into() or explicit clamping used for numeric conversions
• No f64 as usize without prior clamping

Concurrency

• Lock acquisition order is documented when multiple locks are used
• No tokio::sync write guards held across .await without bounded hold time
• Concurrent counters use compare_exchange loops, not load-then-store
• std::sync::Mutex in async context is held only briefly, never across .await

Memory and Performance

• No .clone() on structs with >5 heap-allocated fields in hot paths
• HashMap::with_capacity() / Vec::with_capacity() used when size is known
• Large buffers wrapped in Arc rather than cloned
• Temporary string computations use &str or Cow<str> instead of String

Recursion Safety

• Recursive functions have a depth limit or use iterative traversal
• Tree/cache traversals handle corrupted/cyclic input safely

Testing

• Every test function has at least one assert!
• Tests use .expect("context") not bare .unwrap()
• No println!/eprintln! in production code (use tracing)

Serde

• Structs from untrusted input have #[serde(deny_unknown_fields)]
• #[serde(default)] not used on security-critical fields without validation

Code Hygiene

• No #![allow(dead_code)] at crate root
• No camelCase statics or Hungarian notation
• New string literals don't duplicate existing constants

Severity Classification

• P0 (Block merge): unwrap() in request hot path, silent truncation on user input, lock ordering violation, recursion without depth limit
• P1 (Must fix): Result<_, String> in public API, unnecessary clone in hot path, Box<dyn Error> in trait method
• P2 (Should fix): Missing assert! in test, println! in production, missing with_capacity
• P3 (Nice to fix): Naming convention violation, missing doc comment, as_ptr() vs Arc::ptr_eq

Output Template

## Rust Code Quality Report

### Automated Scan
- unwrap/expect in production: N found
- as casts: N found
- String errors: N found
- println/eprintln: N found

### Findings
- [P1] `path:line` — description
  - Fix: ...
  - Validation: ...

### Verdict
PASS / BLOCKED (list blocking findings)