alt Hacker NewsExn looks very interesting, but to be actionable we need a compatibility layer with thiserror and anyhow since most are using it right now. Moving the goalpost a little we mostly need a core rust solution otherwise your error handling stops at the first library you use that doesn't use exn.
I think they are almost compatible.
`thiserror` helps you define the error type. That error type can then be used with `anyhow` or `exn`. Actually, we have been using thiserror + exn for a long time, and it works well. While later we realize that `struct ModuleError(String)` can easily implement Error without thiserror, we remove thiserror dependency for conciseness.
`exn` can use `anyhow::Error` as its inner Error. However, one may use `Exn::as_error` to retrieve the outermost error layer to populate anyhow.
I ever consider `impl std::error::Error` for `exn::Exn,` but it would lose some information, especially if the error has multiple children.
`error-stack` did that at the cost of no more source:
* https://docs.rs/error-stack/0.6.0/src/error_stack/report.rs....
* https://docs.rs/error-stack/0.6.0/src/error_stack/error.rs.h...