anchor.diff:  open FStar.String
   open FStar.Ident
   open FStar.Errors
  +open FStar.Parser
   
   module Const = FStar.Parser.Const
   module BU = FStar.Util
  
positive.code:     : bool =
      Option.isSome (implementation_of file_system_map key)
  
  (* In public interface *)
  let cache_file_name fn =
    FStar.Options.prepend_cache_dir
      (if Options.lax()
       then fn ^ ".checked.lax"
       else fn ^ ".checked")
  
  let file_of_dep_aux
                  (use_checked_file:bool)
  
negative.code:           //     since if the implementation was on the command line, it must exist because of option validation
            raise_err (Errors.Fatal_MissingImplementation,
                       BU.format1 "Expected an implementation of module %s, but couldn't find one" key)
          | Some f -> maybe_use_cache_of f
  
  let file_of_dep = file_of_dep_aux false
  
  