For a lot of stuff what I really want is golang but with better generics and result/error/enum handling like rust.
I cautiously agree, with the caveat that while I thought I would really like Rust's error handling, it has been painful in practice. I'm sure I'm holding it wrong, but so far I have tried: * thiserror: I spend ridiculous and unpredictable amounts of time debugging macro expansions * manually implementing `Error`, `From`, etc traits: I spend ridiculous though predictable amounts of time implementing traits (maybe LLMs…
Is it a new error condition that downstream consumers want to know about so they can have different logic? Add the enum variant. The entire point of this pattern is to do what typed exceptions in Java were supposed to do, give consuming code the ability to reason about what errors to expect, and handle them appropriately if possible.
If your consumer can't be reasonably expected to recover? Use a generic failure variant, bonus points if you stuff the inner error in and implement std::Error so consumers can get the underlying error by calling .source() for debugging at least.
> By contrast, I just wrap Go errors with `fmt.Errorf("opening file `%s`: %w", filePath, err)` and handle any special error cases with `errors.As()` and similar and move on with life. It maybe doesn't feel _elegant_, but it lets me get stuff done.
Nothing stopping you from doing the same in Rust, just add a match arm with a wildcard pattern (_) to handle everything but your special cases.
In fact, if you suspect you are likely to add additional error variants, the `#[non_exhaustive]` attribute exists explicitly to handle this. It will force consumers to provide a match arm with a wildcard pattern to prevent additions to the enum from causing API incompatibility. This does come with some other limitations, so RTFM on those, but it does allow you to add new variants to an Error enum without requiring a major semver bump.