{"ast_node_type":"other","tokens":[{"end":56,"kind":"keyword","start":0,"text":"implicit_region_bound:"}]}
        implicit_region_bound: Option<ty::Region<'tcx>>,
        region_bound_pairs: &'cx RegionBoundPairs<'tcx>,
        caller_bounds: &'cx [ty::PolyTypeOutlivesPredicate<'tcx>],