{"ast_node_type":"variable","tokens":[{"end":43,"kind":"keyword","start":0,"text":"let"}]}
        let late_bound_in_projection_term =
        //     for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
            tcx.collect_constrained_late_bound_regions(pred.map_bound(|pred| pred.projection_term));