scala> def f = list.zipWithIndex map { case (a,i) => ??? }

...
def f(): List = $line6.iw.list().zipWithIndex(immutable.this.List.canBuildFrom()).$asInstanceOf[List]().map({
  ((x0$1: Tuple2) => iw.this.$anonfun$f$1(x0$1))
}, immutable.this.List.canBuildFrom()).$asInstanceOf[List]();
    final <artifact> private[this] def $anonfun$f$1(x0$1: Tuple2): Nothing = {
      case <synthetic> val x1: Tuple2 = x0$1;
      case4(){
        if (x1.ne(null))
          matchEnd3(scala.Predef.???())
        else
          case5()
      };
      case5(){
        matchEnd3(throw new MatchError(x1))
      };
      matchEnd3(x: Nothing){
        x
      }
    };