Implement Standard Traits for Public Errors

RUST-IMPLEMENT-STANDARD-TRAITS-FOR-PUBLIC-ERRORS

Summary

Make reusable public errors implement the standard diagnostic traits where appropriate. This lets callers compose, display, chain, and inspect errors in ordinary Rust workflows.

Rule

Implement Debug, Display, and std::error::Error for reusable public errors.

Why

Public errors cross boundaries into callers, logs, tests, and user messages. Implementing Debug, Display, and std::error::Error when appropriate makes errors composable and inspectable in standard Rust workflows.

Helps

Helps public errors work with ?, error chains, logs, test output, and common error-reporting libraries.

Limits

Application-internal errors can be simpler. Public library errors should avoid losing sources or forcing callers to parse strings.

Agent Instruction

Implement `Debug`, `Display`, and `std::error::Error` for public errors that cross into callers,
logs, tests, and user messages.

Mechanisms

Implement or derive Debug, write actionable Display, implement std::error::Error, expose sources, and consider thiserror when it reduces boilerplate without hiding policy.