It's certainly true that today (3 March 2017) there is still a gap between DOT and the current Scala compiler (version 2.12.1) -- just as there is a gap between

It's certainly true that today (3 March 2017) there is still a gap between DOT and the current Scala compiler (version 2.12.1) -- just as there is a gap between Haskell and the lazy lambda calculus. However, as a conceptual guide what Scala is, DOT is quite helpful. With time DOT will become even more helpful In general, it's OK for there to be a gap between a real programming language, and its theoretical toy model. That's the gap between theory and practise. Why would you care about theory if it was as complex as practise? The ideal case (embodied in the lambda-calculus) is that the theory is much easier, but looses only a modest amount of precision.