fails to compile. i'm not sure why - shouldn't "d" just represent *any type*, so 999 is legal to put in there?

compileplz.hs

class WithInt c where
  combinate :: Integral i => i -> c -> [(i,c,d)]

data Wut = Wut deriving (Show)

instance WithInt Wut where 
  combinate i w = if (i == 0)
                    then []
                    else (i,w,999):combinate (i - 1) w


main = let l :: [(Int, Wut, Int)]
           l = combinate 8 Wut
       in putStrLn $ show $ l