The scala compiler has some useful flags, that can do some linting on unused variables, imports etc.

scalacOptions := Seq("-unchecked", "-deprecation", "-encoding", "UTF-8", "-Xfatal-warnings", "-Xlint:missing-interpolator", "-Ywarn-unused", "-Ywarn-dead-code", "-Ywarn-numeric-widen")

I found these flags on this very usefull blog post:
scala compiler review code warnings