text: function unreachable()
  {
      throw new Error("NG");
  }
  
  function *gen()
  {
      unreachable();
  }
  
  var g = gen();
  var error = new Error("OK");
  var thrown = null;
  try {
      g.throw(error);
  } catch (e) {
      thrown = e;
  }
  if (thrown !== error)
      unreachable();
  