Internals, mostly, I think. Correctness. According to Phillips, the internals of scalac are a complete mess, and the runtime generated code is also non-ideal. B

Internals, mostly, I think. Correctness. According to Phillips, the internals of scalac are a complete mess, and the runtime generated code is also non-ideal. Basically, all sorts of software best practices are being broken to achieve performance and ensure Scala is a superset of Java.