abstract class $EDIBLE is
  eat;
end;

class FOOD < $EDIBLE is
  readonly attr name:STR;
  eat is
    #OUT + "eating " + self.name + "\n";
  end;
  create(name:STR):SAME is
    res ::= new;
    res.name := name;
    return res;
  end;
end;

class CAR is
  readonly attr name:STR;
  create(name:STR):SAME is
    res ::= new;
    res.name := name;
    return res;
  end;
end;

class FOODBOX{T < $EDIBLE} is
  private attr list:LLIST{T};
  create:SAME is
    res ::= new;
    res.list := #;
    return res;
  end;
  add(c :T) is
    self.list.insert_back(c);
  end;
  elt!:T is loop yield self.list.elt!; end; end;
end;

class MAIN is
  main is
    box  ::= #FOODBOX{FOOD}; -- ok
    box.add(#FOOD("Banana"));
    box.add(#FOOD("Amanita Muscaria"));

    box2 ::= #FOODBOX{CAR};  -- not ok
    box2.add(#CAR("Punto")); -- but compiler let it pass!

    -- eat everything
    loop box.elt!.eat; end;
  end;
end;