Ohno Macros Impl

Implementation of the procedural macros for the ohno crate.

This crate holds the logic behind:

• #[derive(Error)] - Automatically implement error traits
• #[enrich_err("message")] - Add error enrichment with file/line information to function errors
• #[ohno::error] - Turn a plain struct into an error type

Do not depend on this crate directly. Use the re-exports from ohno instead.