interface iflush2cb {
   in void doit();
   out void cb();

   behaviour {
      bool idle = false;
      [idle] {
         on doit: {}
      }
      [!idle] {
         on doit: illegal;
         on inevitable: {cb; cb;}
      }
   }
}

component flush2cb {
   provides iflush2cb p;
   requires iflush2cb r;

   behaviour {
      bool idle = false;
      [idle] {
         on p.doit(): r.doit();
	     on r.cb: illegal;
      }
      [!idle] {
         on p.doit: illegal;
         on r.cb(): { p.cb(); }
      }
   }
}