Modularizing Language Features sucks.

build.sbt

      scalacOptions <<= scalaVersion.map { sv =>
        if (sv.startsWith("2.10")) {
          Seq(
            "-deprecation",
            "-language:dynamics",
            "-language:postfixOps",
            "-language:reflectiveCalls",
            "-language:implicitConversions",
            "-language:higherKinds",
            "-language:existentials",
            "-language:reflectiveCalls",
            "-language:experimental.macros"
          )
        } else {
          Seq("-deprecation")
        }
      }

"-language:_"

で、全部有効にできたはず