anchor.diff:  
     let env, finish_name_tracking = track_name_changes env in // begin name tracking…
   
  -  match with_captured_errors (snd env)
  +  match with_captured_errors env
             (fun () -> Some (tc_prims_and_deps env st.prepl_fname)) with
     | Some (deps, repl_deps, env) ->
       on_successful_init (finish_name_tracking env) deps repl_deps
  
positive.code:   TcEnv.cleanup_interactive env
  
  let with_captured_errors' env f =
    try
      f ()
    with
  
negative.code:   else with_captured_errors' env f
  
  let check_frag (dsenv, (env:TcEnv.env)) curmod frag =
    with_captured_errors (dsenv, env) (fun () ->
      match tc_one_fragment curmod dsenv env frag with
      | Some (m, dsenv, env) ->
        Some (m, (dsenv, env), FStar.Errors.get_err_count())
  