anti-patterns

name	anti-patterns
description	Identify and refactor Rust anti-patterns and clippy anti-idioms. Use when reviewing Rust code for smells, hunting anti-patterns to fix or remove, or refactoring code that clones to satisfy the borrow checker, takes &String/&Vec parameters, unwraps on fallible paths, or returns sentinel values instead of Option/Result.
license	MIT

Rust Anti-Patterns

Catalog of Rust anti-patterns and clippy anti-idioms for reviewers and implementers actively hunting code to fix or remove. Complements /rust:troubleshooting (which teaches the idiomatic GOOD patterns) by naming the BAD patterns explicitly, with detection hints.

When to Use This Skill

Activate when:

• Reviewing a Rust diff or module for anti-patterns
• Refactoring code flagged by clippy or code review
• Deciding whether a .clone(), &Vec<T> parameter, unwrap(), or sentinel return value is a bug to fix

Sources

Rust Design Patterns book (anti-patterns, idioms) and the Clippy lint index — full attribution per entry in references/anti-patterns.md, dated URLs in sources.md.

Example

// BAD: clippy::ptr_arg — forces callers to hold an owned Vec
fn process(data: &Vec<i32>) { /* ... */ }

// GOOD: accepts a Vec, an array, or a slice via deref coercion
fn process(data: &[i32]) { /* ... */ }

The full catalog (9 entries) is in references/anti-patterns.md.

Usage Guidelines

1. Scan for the pattern — check the diff or module against references/anti-patterns.md
2. Confirm it's not deliberate — a restraint: comment or documented tradeoff can justify what looks like an anti-pattern; anti-patterns are defaults to avoid, not absolute bans
3. Fix at the root — apply the GOOD replacement, don't just silence the lint
4. Cite the source — when flagging in review, reference the anti-pattern name so the author can look it up

Anti-Fabrication

Every entry in references/anti-patterns.md cites its source URL. Do not assert a clippy lint name, its default-enabled status, or a "this catches N% of cases" claim without verifying against the linked clippy documentation — see /core:anti-fabrication.