And this is from a programmer that is not happy with Scala. Every single time I've upgraded the compiler there is a breaking change. They don't strictly follow semver. Most recently upgrading from the 2.11 to 2.13 compiler they made breaking serial version uid changes (I know don't use java serialization, but that wasn't my decision) and none of it was noted in the release notes.
When it comes to super complex just look at any of the type signatures of the standard library for collections:
def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[IndexedSeq[A], B, That]): That
Comparing this to Java it is "super complex". IntelliJ can't even figure out the types sometimes.