SBT FAQ: How do I set the desired Scala compiler version in the SBT build.sbt configuration file?
Set the value of the scalaVersion variable in your SBT build.sbt file. For instance, to use Scala 2.9.2, put an entry like this in the build.sbt file:
scalaVersion := "2.9.2"
To use Scala 2.10.0, put an entry like this in the build.sbt file:
scalaVersion := "2.10.0"
I haven't tested this yet, but it looks like you can use the latest version of Scala, such as the latest version of Scala 2.10, with this syntax:
scalaVersion := "2.10.0-SNAPSHOT" resolvers += Resolver.sonatypeRepo("snapshots")
See the SBT "How To" for more information on setting the Scala version, and other build.sbt topics.