src/HOL/Tools/BNF/bnf_fp_n2m.ML

     val ((gAT, gBT), gT) = `dest_funT (fastype_of g);
   in
     Const (@{const_name sum_map}, fT --> gT --> mk_sumT (fAT, gAT) --> mk_sumT (fBT, gBT)) $ f $ g
   end;
 
-fun construct_mutualized_fp fp fpTs fp_sugars bs resBs (resDs, Dss) bnfs lthy =
+fun construct_mutualized_fp fp fpTs (fp_sugars : fp_sugar list) bs resBs (resDs, Dss) bnfs lthy =
   let
     fun steal_fp_res get =
       map (fn {fp_res, fp_res_index, ...} => nth (get fp_res) fp_res_index) fp_sugars;
 
     val n = length bnfs;