[virtualwhys]

> The main issue at the end of the day is compile time

For deployment, sure, but for daily dev the vast majority of one's time should be spent taking advantage of sbt's incremental build feature; there the compile hit is pretty neglible (particularly when you break out your application into sub projects/modules).

Even after the proposed Scala overhaul (i.e. Dotty in around 4 years time) it's unlikely that clean builds will be blazing fast.

To put in perspective, right now scalac is roughly 10X slower than javac. Scala compiler team is banking on getting a speed up by generating Java 8 closures under the hood with Scala 2.12; that will mean less code for scalac to generate.

Beyond that, trimming down language features and streamlining the type system will provide further compile time reduction. As you say, lots of room for improvement ;-)