interface ihello
{
  in void hello();

  behaviour
  {
    on hello: {}
  }
}

component hello_guard_two
{
  provides ihello h;
  requires iworld w;

  behaviour
  {
    bool b = false;
    [true] {
      [b] on h.hello(): {
        b=!b;w.cruel ();
      }
      [!b] on h.hello(): {
        b=!b;w.cruel ();
      }
    }
  }
}

interface iworld
{
  in void cruel();
  in void world();

  behaviour
  {
    on cruel: {}
    on world: {}
  }
}