{"ast_node_type":"function","tokens":[{"end":100,"kind":"keyword","start":0,"text":"pub(super)"}]}
    pub(super) fn upper_bounds(&self, scc0: ConstraintSccIndex) -> impl Iterator<Item = RegionVid> {
    /// Find all universal regions that are required to outlive the given SCC.
        let mut duplicates = FxIndexSet::default();