{"ast_node_type":"other","tokens":[{"end":34,"kind":"keyword","start":0,"text":"ty::Covariant"}]}
                ty::Covariant => {
                // [rd]: https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference/placeholders_and_universes.html
                    infcx.enter_forall(b, |b| {