let env_program (prog : NAst.program) : Types.type_env =
  let lcn = list_canonical_names prog in
    let fcd = first_canonical_duplicate lcn in
      if Option.is_some(fcd)
      then
        let fcd' = Option.get fcd in
          raise(error_duplicate_variable
            (CanonicalName.to_string
              (fcd'.NAst.source_file_decl.NAst.type_canonical_name))
            fcd'.NAst.source_file_decl.NAst.type_pos)
      else
        let m = TEnv.empty in
          match prog with
          | [] -> m
          | _ -> List.fold_left
                 (fun map sf ->
                TEnv.add
              sf.NAst.source_file_decl.NAst.type_canonical_name
              (env_type_decl sf.NAst.source_file_decl info)
              map)
             m
             prog