vals.scala

object vals {
  val fn: Int => String = (n) => n.toString
  val f = fn _ // works because fn is a method

  def method = {
    val fn: Int => String = (n) => n.toString
    val f = fn _ // doesn't work because fn is not a method
  }
}

http://stackoverflow.com/questions/17484457/unable-to-understand-placeholder-behavior-in-scala-function-application

Eew, that's subtle... Nice catch, though!

@lukaseder someone else's catch, but I agree.