{"ast_node_type":"function","tokens":[{"end":65,"kind":"keyword","start":0,"text":"fn"}]}
    fn start_region(sup: RegionVid, sub: RegionVid) -> RegionVid;
pub(crate) trait ConstraintGraphDirection: Copy + 'static {
    fn end_region(sup: RegionVid, sub: RegionVid) -> RegionVid;