{"ast_node_type":"other","tokens":[{"end":10,"kind":"keyword","start":0,"text":"),"}]}
        ),
            len.try_to_target_usize(fx.tcx).expect("expected monomorphic const in codegen") as i64,
        (&ty::Dynamic(data_a, _, src_dyn_kind), &ty::Dynamic(data_b, _, target_dyn_kind))