What languages are IDE-friendly?

Some languages are much easier to support in an IDE than others. Their respective plugins have more features and work faster. That turns out to heavily depend on the language design. We'll look at various languages (Java, Kotlin, Groovy, Scala, C++, PHP, Haskell, etc) and framework features and investigate which of them are mostly harmless and which can severely upset the IDE, its developers, and users.