abstract class A {
  def parseCharRef(ch: () => Char, nextch: () => Unit, reportSyntaxError: String => Unit): String = {
    while (ch() != ';') {
      ch() match {
        case 'a' | 'b' =>
          reportSyntaxError("plop")
        case _ =>
          reportSyntaxError("plip")
      }
      nextch()
    }
    "plop"
  }
}