Better error reporting in tallyingtest

tests/libtest/tallyingTest.ml

@@ -339,8 +339,9 @@ let test_tallying =
               let s_sigma = Tallying.(s $$ sigma) in
               let t_sigma = Tallying.(t $$ sigma) in
               assert_equal ~pp_diff:(fun fmt _ ->
-                  Format.fprintf fmt "s @ sigma_i = %a\n" Types.Print.pp_type s_sigma;
-                  Format.fprintf fmt "t @ sigma_i = %a\n" Types.Print.pp_type t_sigma
+                Format.fprintf fmt "sigma_i = %a\n" Types.Tallying.CS.pp_e sigma;
+                Format.fprintf fmt "s @@ sigma_i = %a\n" Types.Print.pp_type s_sigma;
+                Format.fprintf fmt "t @@ sigma_i = %a\n" Types.Print.pp_type t_sigma
               ) (Types.subtype s_sigma t_sigma) true
             ) sigma
           ) l