I really liked Kotlin in the beginning, but it's error handling story is non-existent. They removed the ONLY decent (not great, very flawed) complier validated method for error handling, checked exceptions, and gave us nothing in return.
It'd be so easy to simply do exactly what Rust does. Kotlin already has the ADT stuff necessary, all we need is some kind of "bubbling" operator, like the ? in Rust. Because right now, it's all just super horrible manual checks everywhere.
Different strokes... I think Java checked exceptions are a design flaw and the fact that no other language that I'm aware of has them is telling. Maybe it even was a good idea in the beginning, but it was just horribly abused by basically every library under the sun - no, I don't want to catch some low-level exception when I'm calling your library, thank you very much.
I don't mind making error handling part of compile-time checking (as long as you can opt out by something like unchecked exceptions), but that should be done in a way that is compatible with the regular type system. That way you can abstract over error handling in ways that using checked exceptions disallows.
IIRC, the stance of the Kotlin team is that if you want compile-time checked error handling, you should use Result types. Maybe the ergonomics aren't as good as in Rust, but if you use something like arrow, they're still decent.
It'd be so easy to simply do exactly what Rust does. Kotlin already has the ADT stuff necessary, all we need is some kind of "bubbling" operator, like the ? in Rust. Because right now, it's all just super horrible manual checks everywhere.