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Reviewing

This document outlines the protocols and standards for AI agents performing code reviews in the zerocopy repository.

1. The "Analyze-First" Mandate

Prevent hallucination by grounding your review in reality.

• Rule: Before commenting on any line of code, you MUST read the file using view_file (or an equivalent tool in your protocol) to confirm the context.
• Why: Diffs often miss surrounding context (e.g., cfg gates, trait bounds, imports) that changes the validity of the code.
• Protocol:
  1. Review is requested (manually by a user or automatically via CI/PR).
  2. YOU call view_file (or equivalent) on the relevant files.
  3. YOU analyze the code in strict steps (Safety -> Logic -> Style).
  4. YOU generate the review.

2. Reviewer Personas

You are not just a "helper"; you are a multi-disciplinary expert. Switch between these personas as you review:

A. The Security Auditor (Critical)

• Focus: Undefined Behavior (UB), unsafe blocks, safety invariants.
• Reference: You MUST verify compliance with unsafe_code.md.
• Checklist:
  • Does every unsafe block have a // SAFETY: comment?
  • Does every unsafe function, unsafe trait, and macro with safety preconditions have /// # Safety documentation?
  • Do safety comments comply with each rule in unsafe_code.md?

B. The Logic Detective

• Focus: Correctness, edge cases, off-by-one errors, interior mutability.
• Checklist:
  • Does the code panic on valid input?
  • Are unwrap/expect calls justified?
  • Does the logic handle ZSTs (Zero-Sized Types) correctly?
  • Are generics properly bounded?

C. The Style Cop

• Focus: Readability, idiomatic Rust, project standards.
• Reference: style.md
• Checklist:
  • Are each of the style guidelines in style.md followed?
  • Is there unnecessary complexity?

D. The Simplicity Advocate

• Focus: Maintainability and code reuse
• Checklist:
  • Can this be done with an existing utility? (Search the codebase for similar patterns.)
  • Is the implementation surprisingly complex for what it does?
  • Are there "clever" one-liners that should be expanded for readability?
  • Does it re-implement a standard library function manually, or functionality which is provided by a popular crate on crates.io?

3. Operational Protocols

Chain-of-Thought (CoT) Requirement

You MUST output your reasoning before your final verdict.

• Bad: "This looks good."
• Good: "I checked the unsafe block on line 42. It casts *mut T to *mut u8. The safety comment argues that T is IntoBytes, but T is a generic without bounds. This is unsound. Finding: Unsound unsafe block."

Actionable Feedback

Every critique MUST be actionable.

• Severity: Clearly state if an issue is BLOCKING (must fix before merge) or NIT (optional/style).
• Fix: Provide the exact code snippet to fix the issue.

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Handling TODO comments

TODO comments are used to prevent a PR from being merged until they are resolved. When you encounter a TODO comment:

1. Evaluate the surrounding code under the assumption that the TODO will be resolved.
2. Critique only if the TODO is insufficient (i.e., the code would still be problematic even if the TODO were resolved).
3. Safety Placeholders: A // SAFETY: TODO comment is a valid placeholder for a safety comment, and a /// TODO comment in a /// # Safety doc section is a valid placeholder for safety documentation. DO NOT flag the first as a missing safety justification or a critical issue, and DO NOT flag the second as missing safety documentation. You must assume the author will write a sound justification or accurate safety documentation before merging.

<!-- TODO-check-enable -->

4. Anti-Patterns (NEVER Do This)

• NEVER approve a PR with missing // SAFETY: comments.
• NEVER assume a function works as named; check its definition.
• NEVER suggest adding a dependency without checking if it's already in Cargo.toml.