In my experience IntelliJ is a bad Scala IDE. While it has lots of cool advanced features, none of them make up for not being able to compile the basic language accurately: what good is an IDE where I can't 100% rely on getting a red underline for invalid code and no red underlines for valid code?

The parts where IntelliJ has always fallen down on Scala seem to be precisely the parts that are missing from Kotlin. I can't help feeling that the JetBrains team just "doesn't get" higher-kinded types at all. Which is a shame, because there is a lot of good stuff in Kotlin otherwise.