{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
            let lt = to_lt; // FIXME: Involve rustc LUB and SUB flag checks
            // from `&mut T` to `&U`.
            let derefd_from_ty = TyKind::Ref(to_mt, lt.clone(), referent_ty).intern(Interner);