anchor.diff:              Util.print1 "%s\n" fail;
               let env = tc.reset_mark env_mark in
               go stack curmod env in
  -          
  +
             let env_mark = tc.mark env in
             let res = tc.check_frag env_mark curmod text in begin
               match res with
  
positive.code: module U_Syntax = FStar.Syntax.Syntax
  module F_Syntax = FStar.Absyn.Syntax
  let detect_dependencies_with_first_interactive_chunk () =
   try
       let fail msg = 
          if (Options.universes())
          then raise (U_Syntax.Err msg)
          else raise (F_Syntax.Err msg) in
        match find_initial_module_name () with
        | None ->
          fail "No initial module directive found\n"
  
negative.code:           | Some (None, None) ->
                failwith "impossible"
  
    with
    | U_Syntax.Error(msg, r)
    | F_Syntax.Error(msg, r) ->
        failr (parse_msg ^ msg) r
    | U_Syntax.Err msg
    | F_Syntax.Err msg ->
        fail (parse_msg ^ msg)
  
  
  (******************************************************************************************)
  (* The main interactive loop *)
  (******************************************************************************************)
  let interactive_mode (env:'env) (initial_mod:'modul) (tc:interactive_tc<'env,'modul>) =
    if Option.isSome (Options.codegen()) then
      (Util.print_warning "code-generation is not supported in interactive mode, ignoring the codegen flag");
      let rec go (stack:stack<'env,'modul>) (curmod:'modul) (env:'env) = begin
  