This is a long read, but well worth it: one of several ongoing ways in which I think we will be seeing Scala's compile times fall dramatically over the next couple of years! (Using Magnolia instead of shapeless might've had much the same benefit, but that's not the point, here!)https://twitter.com/scala_lang/status/1003639318836105217 …
New tool! 
scalac-profiling
Learn what's slowing down compilation in your project, and remove it! Speed up all the things!
@jvican demos how by speeding up compilation of his project by 8x!
In the scala-lang blog:
https://www.scala-lang.org/blog/2018/06/04/scalac-profiling.html …
scalac-profiling
Learn what's slowing down compilation in your project, and remove it! Speed up all the things!
