anchor.diff:      in
       let unembed_result (t:term) w _ : option<__result<'a>> =
           match hd'_and_args t with
  -        | Tm_fvar fv, [_t; (a, _); (ps, _)] when S.fv_eq_lid fv fstar_tactics_Success_lid ->
  +        | Tm_fvar fv, [_t; (a, _); (ps, _)] when S.fv_eq_lid fv fstar_tactics_Success.lid ->
               BU.bind_opt (unembed' w ea a) (fun a ->
               BU.bind_opt (unembed' w e_proofstate ps) (fun ps ->
               Some (Success (a, ps))))
   
  -        | Tm_fvar fv, [_t; (e, _); (ps, _)] when S.fv_eq_lid fv fstar_tactics_Failed_lid ->
  +        | Tm_fvar fv, [_t; (e, _); (ps, _)] when S.fv_eq_lid fv fstar_tactics_Failed.lid ->
               BU.bind_opt (unembed' w e_exn e) (fun e ->
               BU.bind_opt (unembed' w e_proofstate ps) (fun ps ->
               Some (Failed (e, ps))))
  
positive.code: let embed e r x = FStar.Syntax.Embeddings.embed e x r None id_norm_cb
  let unembed' w e x = FStar.Syntax.Embeddings.unembed e x w id_norm_cb
  
  let hd'_and_args tm =
    let tm = U.unascribe tm in
    let hd, args = U.head_and_args tm in
  
negative.code:     in
      let unembed_exn cb (t:NBET.t) : option<exn> =
          match t with
          | NBETerm.Construct (fv, _, [(s, _)]) when S.fv_eq_lid fv fstar_tactics_TacticFailure.lid ->
              BU.bind_opt (NBETerm.unembed NBETerm.e_string cb s) (fun s ->
              Some (TacticFailure s))
  
  