switch.scala:28: error: could not emit switch for @switch annotated match
  def fail1(c: Char) = (c: @switch) match {
                                    ^
switch.scala:38: error: could not emit switch for @switch annotated match
  def fail2(c: Char) = (c: @switch @unchecked) match {
                                               ^
switch.scala:45: error: could not emit switch for @switch annotated match
  def fail3(c: Char) = (c: @unchecked @switch) match {
                                               ^
three errors found