| Snterm e | Snterml (e, _) -> is_entry_dummy e
| Slist1 x | Slist0 x -> is_symbol_dummy x
| Slist1sep (x,y,false) | Slist0sep (x,y,false) -> is_symbol_dummy x && is_symbol_dummy y
| Snterm e | Snterml (e, _) -> is_entry_dummy e
| Slist1 x | Slist0 x -> is_symbol_dummy x
| Slist1sep (x,y,false) | Slist0sep (x,y,false) -> is_symbol_dummy x && is_symbol_dummy y