m06-error-handling

Rust error handling uses Result for recoverable expected failures, Option when a value may be absent, and panic for unrecoverable bugs. Choose based on whether the calling code can reasonably recover from the specific failure condition.

Use thiserror to design custom error enums for libraries where callers need to match specific error variants. Use anyhow in applications to propagate errors with dynamic context, providing flexible error handling without rigid type definitions.

Add context to Rust errors by using anyhow's `.context()` method during error propagation. This enriches the error chain with descriptive information, allowing you to track exactly where and why an expected failure occurred across function boundaries.

Use unwrap and expect in Rust when a failure indicates an unrecoverable bug rather than an expected runtime failure. They trigger a panic, making them suitable for invariant guarantees where missing values signify broken logic rather than recoverable errors.

Distinguish expected failures from bugs in Rust by assessing recoverability. Expected failures like file-not-found should return Result to allow caller recovery, while bugs like indexing out of bounds should panic to immediately halt execution.