handlers eagerly invoked

Foo.scala

package foo

trait SAM {
  def onSam(): Unit
}

object Foo {
  def main(args: Array[String]): Unit = {
    doFunction { println("1"); println("2") }
    // got <function0>
    // 1 2 1 2

    doSam(body2sam({ println("1"); println("2") }))
    // got foo.Foo$$anon$1@2b86c6b2
    // 1 2 1 2

    doSam { println("1"); println("2") }
    // 1
    // got foo.Foo$$anon$1@416b13c7
    // 2 2
  }

  def doSam(sam: SAM) = { println("got " + sam) ; sam.onSam() ; sam.onSam() }

  def doFunction(f: => Unit) = { println("got " + (f _)) ; f ; f }

  implicit def body2sam(f: => Unit): SAM = new SAM {
    override def onSam = f
  }
}