SpecConstr does not specialise for literal arguments.

I would expect this code to specialize:

{-# NOINLINE bar #-}
bar = goo 0 1
  where
    goo :: Int -> Int -> Int
    goo 0 1 = 1
    goo _ (0) = 3
    goo n x = goo n (x-1)

But after worker-wrapper the go function takes literal ints for which SpecConstr currently doesn't create specializations.