How to get more information about 'feature' flag warning?

Question

When compiling an application with Play2, sometimes these kind of message appears on my terminal :

[info] Compiling 1 Scala source to ~/target/scala-2.10

Answer 1

To see the exact message you need to add "feature" flag in your sbt build definition file:

scalacOptions ++= Seq("-feature")

Why? Scala 2.10 not only introduced new features, but also reshuffled older ones -- some of the most powerful scala features were hidden because they should be used with great responsibility: sometimes they were used mistakingly. That is why SIP-18 has arised. From now on, to access dynamics, higher kinds, existential types and some other things you have to explicitly enable them.