{"ast_node_type":"other","tokens":[{"end":94,"kind":"keyword","start":0,"text":"DefKind::LifetimeParam"}]}
                        DefKind::LifetimeParam | DefKind::Trait | DefKind::TraitAlias => None,
                        // works. Ignore it because it can't have a meaningful lifetime default.
                        dk => bug!("unexpected def_kind {:?}", dk),