case PolyType(tparams, result) =>
        val tparams1 = flipped(mapOver(tparams))
        val result1 = this(result)
        if ((tparams1 eq tparams) && (result1 eq result)) tp
        else PolyType(tparams1, result1.substSym(tparams, tparams1))

object Test {
  val lv: scala.swing.ListView[Any] = ???
  lv.peer.setModel(null)
}

    private def correspondingTypeArgument(lhs: Type, rhs: Type): Type = {
      val TypeRef(_, lhsSym, lhsArgs) = lhs
      val TypeRef(_, rhsSym, rhsArgs) = rhs
      require(lhsSym.owner == rhsSym, s"$lhsSym is not a type parameter of $rhsSym")

      // Find the type parameter position; we'll use the corresponding argument.
      // Why are we checking by name rather than by equality? Because for
      // reasons which aren't yet fully clear, we can arrive here holding a type
      // parameter whose owner is rhsSym, and which shares the name of an actual
      // type parameter of rhsSym, but which is not among the type parameters of
      // rhsSym. One can see examples of it at SI-4365.
      val argIndex = rhsSym.typeParams indexWhere (lhsSym.name == _.name)
      // don't be too zealous with the exceptions, see #2641
      if (argIndex < 0 && rhs.parents.exists(typeIsErroneous))

object Test extends App {
  val comboBox = new ComboBox(List(None))
  comboBox.peer.setModel(new DefaultComboBoxModel())
}