thiserror-expert

Custom error types in Rust use the thiserror crate's #[derive(Error)] macro to automatically implement Display and std::error::Error traits. Define an enum with variants, annotate fields with #[error("...")], and thiserror generates the boilerplate for you, reducing manual implementation.

Use thiserror's #[from] attribute on error enum variants to automatically implement From trait implementations. This enables seamless error propagation—wrap io::Error, parse errors, or other sources directly, and thiserror chains them while preserving context for debugging.

Define error variants with named or positional fields, then use #[error("message with {field}")] to include dynamic data. thiserror's derive macro formats these fields into Display output, making error messages informative without manual Display trait coding.

Yes. Combine #[from] for automatic From implementations with #[source] to mark the underlying error. thiserror generates source() method implementations that let users traverse the error chain and understand root causes, improving debuggability.

Use thiserror for any custom error enum to eliminate repetitive boilerplate. It's ideal when you need transparent error forwarding, source chaining, or rich contextual messages—thiserror handles trait implementations so you focus on error semantics and readability.