src/Pure/Tools/codegen_package.ML

 val serializers = ref (
   Symtab.empty
   |> Symtab.update (
        #ml CodegenSerializer.serializers
        |> apsnd (fn seri => seri
-            (nsp_dtcon, nsp_class)
+            nsp_dtcon
             [[nsp_module], [nsp_class, nsp_tyco], [nsp_const, nsp_overl, nsp_dtcon, nsp_class, nsp_mem, nsp_inst, nsp_instmem]]
           )
      )
   |> Symtab.update (
        #haskell CodegenSerializer.serializers

 fun get_ml_fun_datatype thy resolv =
   let
     val target_data =
       ((fn data => (the o Symtab.lookup data) "ml") o #target_data o CodegenData.get) thy;
   in
-    CodegenSerializer.ml_fun_datatype (nsp_dtcon, nsp_class)
+    CodegenSerializer.ml_fun_datatype nsp_dtcon
       ((Option.map fst oo Symtab.lookup o #syntax_tyco) target_data,
       (Option.map fst oo Symtab.lookup o #syntax_const) target_data)
       resolv
   end;