[wizzwizz4]

They don't get stack traces, for one. (That's arguably the biggest problem with Rust: .unwrap() gives you a stack trace, but has problems; whereas ? erases your stack trace.)

In principle, static analysis could identify unhandled exceptions, then trace the exception, then make that information available to the top-level "Err returned from main" handler. In practice, that's never going to happen in Rust.

[dllthomas]

Sum types can have stack traces by adding a stack trace on creation. `Result<(), &'static str>` does not have a stack trace, but `Result<(), std::backtrace::Backtrace>` sure does. YMMV as to whether it makes sense to do that in any particular circumstance.

[tome]

Sure, if your definition of exceptions includes "must include a stack trace", then sum types can't simulate exceptions. But by that definition Haskell hasn't had exceptions until the last year or two. You might agree with that (I don't) but I'm trying to understand astrange, who said "[Haskell] has exceptions which are a bad language feature, and typed throws which are a worse one". It seems doubtful that "having a stack trace" is part of what he/she considers bad about exceptions, so that aspect is probably not relevant to my line of questioning. What exactly is bad about exceptions? That's the point of me forking off this thread. So far no one has offered an answer.