src/Tools/code/code_target.ML

     val init_names = Name.make_context reserved_syms;
     val name_modl = mk_modl_name_tab init_names module_prefix module_alias code;
     fun add_def (name, (def, deps)) =
       let
         val (modl, base) = dest_name name;
-        fun name_def base = Name.variants [base] #>> the_single;
+        val name_def = yield_singleton Name.variants;
         fun add_fun upper (nsp_fun, nsp_typ) =
           let
             val (base', nsp_fun') =
               name_def (if upper then first_upper base else base) nsp_fun
           in (base', (nsp_fun', nsp_typ)) end;

           |> map (name_modl o fst o dest_name)
           |> distinct (op =)
           |> remove (op =) modlname';
         val qualified =
           imports @ map fst defs
+          |> distinct (op =)
           |> map_filter (try deresolv)
           |> map NameSpace.base
           |> has_duplicates (op =);
         val mk_import = str o (if qualified
           then prefix "import qualified "