{"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"Some(tcx.def_span(trait_def_id).shrink_to_lo()),"}]}
                        Some(tcx.def_span(trait_def_id).shrink_to_lo()),
                        None,
                        if self.tcx().features().const_trait_impl() {