extern T $int$;

interface i
{
  in void e(T t);
  in void c(T t);
  out void a(T t);
  behaviour {
    bool idle = true;
    [idle] {
      on e: idle=false;
      on c: illegal;
    }
    [!idle] {
      on c: idle=true;
      on inevitable: {idle=true;a;}
      on e: illegal;
    }
  }
}

component async_cancel
{
  provides i p;
  behaviour {
    requires dzn.async(T t) defer;
    bool idle = true;
    [idle] on p.e (t): {idle=false; defer.req (t);}
    [!idle] on p.c (t): {idle=true; defer.clr ();}
    [!idle] on defer.ack (t): {idle=true;p.a (t);}
  }
}