Comment by kbolino
11 hours ago
But the argument is not about adding exceptions to the language.
It's about borrowing a technique from languages that do have exceptions (and Rust's own panic unwinding) to implement Rust's existing error handling without making any changes to the language.
The post is light on how this would actually work, though. I think that re-using the name "stack unwinding" is a little misleading. The stack would only unwind if the error was bubbled up, which would only happen if the programmer coded it to. Indeed, the error could just get dropped anywhere up the stack, stopping it from unwinding further.
I think this would be tricky to implement, since the compiler would have to figure out which code actually is on the error path, and any given function could have multiple error paths (as many as one per each incoming error return, if they're all handled differently). It'd also make Result<T,E> even more special than it already is.
All that having been said, if you squint a bit, the end result does vaguely resemble Java's checked exceptions.
And that was really my (unpopular) opinion above - that exceptions and garbage collectors are two examples of runtime/compiler/language features that after some iteration around the corner cases tend to end up in roughly the same place Java did 20+ years ago - as you say, "if you squint a bit".
It is interesting to think why it is so for exceptions specifically. The discussion here offers some of the possible reasons, I think, including violent disagreement of what we all even mean by exceptions vs stack unwinding vs error propagation.