| Tmeta {contents = Some t} -> type_listvar t
| Tvar i | Tvar' i -> Intset.singleton i
| Tarr (a,b) -> Intset.union (type_listvar a) (type_listvar b)
| Tglob (_,l) -> intset_union_map_list type_listvar l
| Tmeta {contents = Some t} -> type_listvar t
| Tvar i | Tvar' i -> Intset.singleton i
| Tarr (a,b) -> Intset.union (type_listvar a) (type_listvar b)
| Tglob (_,l) -> intset_union_map_list type_listvar l