{"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"start_sp:"}]}
            start_sp: rpid_def_span.with_hi(rpid_def_span.lo() + BytePos(4)),
        err.subdiagnostic(SuggestBoxingForReturnImplTrait::ChangeReturnType {
            end_sp: rpid_def_span.shrink_to_hi(),