While I agree that compilation of dynamically typed languages is more challenging, inference for advanced typing systems is full of problems: - How to ensure t

While I agree that compilation of dynamically typed languages is more challenging, inference for advanced typing systems is full of problems: - How to ensure that the inference algorithm is correct. - How to design typing systems that are expressive, yet lightweight, and have enough type inference to be usable in practise. - How to deal with concurrency and parallelism. None of these problems is really solved. In practise even making type inference fast is a challenge, e.g. in older versions of the Scala compiler, type inference was really slow due to implicits.