{"ast_node_type":"variable","tokens":[{"end":78,"kind":"keyword","start":0,"text":"let"}]}
        let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
    ) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
            a_is_expected: false, // when coercing from `a` to `b`, `b` is expected