Clash.Signal.Delayed.feedback is wrong

[christiaanb]

accumX :: DSignal dom d Bool -> DSignal dom d Int -> DSignal dom d Int
accumX restart x = feedback $ \q -> 
  let d = x + mux restart 0 q
      z = delayN d1 0 d
  in (q, z)

and

accumY :: DSignal dom d Bool -> DSignal dom d Int -> DSignal dom d Int
accumY restart x = feedback $ \q -> 
  let d = x + mux restart 0 q
      z = delayN d1 0 d
   in (d, z)

have the same delay signature (no delay), while accumX one outputs x + 0 when restart is True after one cycle; while accumY outputs it immediately.

With antiDelay we can see this distinction in the type signature:

accumD1 :: DSignal dom d Bool -> DSignal dom d Int -> DSignal dom (d + 1) Int
accumD1 restart x =
  let d = x + mux restart 0 (antiDelay d1 q)
      q = delayN d1 0 d
   in q

and

accumD0 :: DSignal dom d Bool -> DSignal dom d Int -> DSignal dom d Int
accumD0 restart x =
  let d = x + mux restart 0 (antiDelay d1 q)
      q = delayN d1 0 d
   in d

We should deprecate feedback and move antiDelay from the "experimental" bracket, as it is clearly the better function for making feedback loops in a context where we want to keep track of delay at the type level.