At a high level, all non-trivial programming is composition. And (see principle of encapsulation) the vast majority of errors shouldn't be recovered and just need to be propagated out.
Then, to be useful, errors need enough information to be diagnosed or investigated. It seems like this should have been a straight-forward requirement in the language design.
A "diagnostics" pattern has emerged in the community to optionally request extra information about a failure. You can pass a pointer to the diagnostic (it can be on the stack) and get the extra info back. It's just a more explicit version of what would otherwise happen in a language with error payloads.
> zig has pretty good error traces by default
These seem rather conditional. If I need to run release-fast in prod, say, do we loose these error traces (for bugs)?
Minor correction: stack traces are available on all build modes, but different build modes have different defaults. See: std.Options.allow_stack_tracing
Yes, it has error return traces.