component EventNotHandled
{
  provides IA pp;
  requires IB rp;

  behaviour
  {
    bool b = false;
    [b] on pp.ia(): rp.ia();
  }

  // Simulate EventNotHandled =>
  //   pp.ia (implicitly) illegal
  // if the following trace is performed:
  //   pp.ia
}

interface IA
{
  in void ia();

  behaviour
  {
    on ia: {}
  }
}

interface IB
{
  in void ia();
  out void oa();

  behaviour
  {
    on ia: illegal;
    on ia: {}
  }
}