simplify foldMap interface to avoid having the silly fn interface

libs/cardano-ledger-test/src/Test/Cardano/Ledger/Constrained/Conway/Utxo.hs

@@ -152,7 +152,7 @@ utxoTxSpec env st =
                                     outputList
                                 depositSum =
                                   foldMap_
-                                    (composeFn fstFn toGenericFn)
+                                    fst_
                                     proposalsList
                              in outputSum + depositSum + ctbTxfee + ctbTreasuryDonation ==. totalValueConsumed
                           ]

libs/constrained-generators/src/Constrained/Base.hs

@@ -3664,17 +3664,25 @@ sum_ ::
   ) =>
   Term fn [a] ->
   Term fn a
-sum_ = app (foldMapFn idFn)
+sum_ = foldMap_ id
 
 foldMap_ ::
+  forall fn a b.
   ( BaseUniverse fn
   , Foldy fn b
   , HasSpec fn a
   ) =>
-  fn '[a] b ->
+  (Term fn a -> Term fn b) ->
   Term fn [a] ->
   Term fn b
-foldMap_ fn = app (foldMapFn fn)
+foldMap_ f = app $ foldMapFn $ toFn $ f (V v)
+  where
+    v = Var (-1) :: Var a
+    toFn :: forall b. HasCallStack => Term fn b -> fn '[a] b
+    toFn (App fn (V v' :> Nil)) | Just Refl <- eqVar v v' = fn
+    toFn (App fn (t :> Nil)) = injectFn $ Compose fn (toFn t)
+    toFn (V v') | Just Refl <- eqVar v v' = idFn
+    toFn _ = error "foldMap_ has not been given a function on the form \\ x -> f (g ... (h x))"
 
 -- Language constructs ----------------------------------------------------
 

libs/constrained-generators/src/Constrained/Test.hs

@@ -585,7 +585,7 @@ listSumElemRange = constrained $ \xs ->
 
 listSumPair :: Numbery a => Spec BaseFn [(a, Int)]
 listSumPair = constrained $ \xs ->
-  [ assert $ foldMap_ (composeFn fstFn toGenericFn) xs ==. 100
+  [ assert $ foldMap_ fst_ xs ==. 100
   , forAll' xs $ \x y -> [20 <. x, x <. 30, y <. 100]
   ]