{-# RULES
"fold/build" foldr k z (build g) = g k z
  #-}

{-# RULES
"fusable/aux"
  fusable x (aux y) =
    faux x y
  #-}

{-# RULES
"map/map"
  map
    f
    (map g xs) =
    map
      (f . g)
      xs
  #-}