Add comment about split/splitGen deprecation in fusion benchmark

Co-authored-by: Simon Jakobi <simon.jakobi@gmail.com>
Assisted-by: Claude (accounts/fireworks/models/glm-5[1m])

Author: sjakobi

prettyprinter/bench/Fusion.hs

@@ -18,10 +18,6 @@ import           Prettyprinter
 import           Prettyprinter.Render.Text
 import qualified Text.PrettyPrint.ANSI.Leijen as WL
 
-#if !(APPLICATIVE_MONAD)
-import Control.Applicative
-#endif
-
 
 
 main :: IO ()
@@ -47,12 +43,14 @@ benchOptimize = env randomShortWords benchmark_
     randomShortWords' :: Int -> State StdGen [Text]
     randomShortWords' n = replicateM n randomShortWord
 
+    -- Note: 'split' is deprecated in random >= 1.2 in favor of 'splitGen'.
+    -- We could use 'splitGen' when support for GHC < 9.0 is dropped.
     randomShortWord :: State StdGen Text
     randomShortWord = do
         g <- get
         let (l, g') = randomR (0, 5) g
             (gNew, gFree) = split g'
-            xs = take l (randoms gFree)
+            xs = take l (randoms gFree :: [Char])
         put gNew
         pure (T.pack xs)