{"ast_node_type":"function","tokens":[{"end":80,"kind":"keyword","start":0,"text":"fn"}]}
    fn successors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node> {
impl<'a, 'tcx, D: ConstraintGraphDirection> graph::Successors for RegionGraph<'a, 'tcx, D> {
        self.outgoing_regions(node)