src/Pure/codegen.ML

     val {codegens, tycodegens, consts, types, preprocs, modules, test_params} =
       CodegenData.get thy;
     val tc = Sign.intern_type thy s;
   in
     case Symtab.lookup (snd (#types (Type.rep_tsig (Sign.tsig_of thy)))) tc of
-      SOME (Type.LogicalType i, _) =>
+      SOME ((Type.LogicalType i, _), _) =>
         if num_args_of (fst syn) > i then
           error ("More arguments than corresponding type constructor " ^ s)
         else (case AList.lookup (op =) types tc of
           NONE => CodegenData.put {codegens = codegens,
             tycodegens = tycodegens, consts = consts,