Dealing with SIP-18 (language imports) in the presence of cross-compilation in build.sbt

build.sbt

scalaVersion := "2.10.0"
 
// Let's support all "modern" Scala versions.
crossScalaVersions := Seq(
  "2.9.3-RC1",
  "2.9.2",
  "2.9.1", "2.9.1-1",
  "2.9.0", "2.9.0-1",
  "2.8.0", "2.8.1", "2.8.2"
)
 
// These options will be used for *all* versions.
scalacOptions ++= Seq(
  "-deprecation",
  "-unchecked"
)
 
// These language flags will be used only for 2.10.x.
// Uncomment those you need, or if you hate SIP-18, all of them.
// Do you know a more future-proof way to compare Scala version strings?
// Please let me know!
// Suggestion from Mike Pilquist: https://github.com/cjmx/cjmx/blob/master/build.sbt#L24
scalacOptions <++= scalaVersion map { sv =>
  if (sv startsWith "2.10") List(
    "-feature"
    // "-language:postfixOps",                                                                                        
    // "-language:reflectiveCalls",                                                                                   
    // "-language:implicitConversions"
    // "-language:higherKinds",                                                                                     
    // "-language:existentials",                                                                                    
    // "-language:experimental.macros",                                                                             
    // "-language:experimental.dynamics"                                                                           
  )
  else Nil
}

Good point @aloiscochard, thanks. This gist will only work in cases that you're not using 2.10 features and are merely trying to support 2.10.