These are things that I found annoying writing a complex library in Kotlin. While I am also a Scala developer, these should not necessarily be juxtaposed w/ Scala (even if I reference Scala) as some of my annoyances are with features that Scala doesn't even have. This is also not trying to be opinionated on whether Kotlin is good/bad (for the record, I think it's good). I have numbered them for easy reference. I can give examples for anything I am talking about below upon request. I'm sure there are good reasons for all of them.
- Arrays in data classes break equals/hashCode and ask you to overload it. If you are going to need to overload it and arrays have no overridability, why not make the least-often use case (the identity-comparison equals) the exception?