Change type Bwd (CSignal dom a) from Signal dom () to ()

There is no reason it should be a `Signal` on the backwards, it just
leads to syntactic noise.

Author: martijnbastiaan

clash-protocols-base/src/Protocols/Plugin.hs

@@ -64,7 +64,7 @@ instance (C.KnownNat n) => Protocol (C.Vec n a) where
 -- XXX: Type families with Signals on LHS are currently broken on Clash:
 instance Protocol (CSignal dom a) where
   type Fwd (CSignal dom a) = C.Signal dom a
-  type Bwd (CSignal dom a) = C.Signal dom ()
+  type Bwd (CSignal dom a) = ()
 
 -- | @circuit-notation@ plugin repurposed for "Protocols".
 plugin :: GHC.Plugin

clash-protocols/src/Protocols/Df.hs

@@ -960,9 +960,9 @@ unsafeFromMaybe = circuit $ \maybes -> do
   idC -< (as1, droppeds)
  where
   go2 ::
-    (Signal dom (Maybe a), (Signal dom Ack, Signal dom ())) ->
-    (Signal dom (), (Signal dom (Maybe a), Signal dom (C.Unsigned n)))
-  go2 (fwdA, (ackB, _)) = (C.pure (), C.mealyB go1 (Nothing, 0) (fwdA, ackB))
+    (Signal dom (Maybe a), (Signal dom Ack, ())) ->
+    ((), (Signal dom (Maybe a), Signal dom (C.Unsigned n)))
+  go2 (fwdA, (ackB, _)) = ((), C.mealyB go1 (Nothing, 0) (fwdA, ackB))
 
   go1 ::
     (Maybe a, C.Unsigned n) ->

clash-protocols/src/Protocols/Internal.hs

@@ -104,7 +104,7 @@ instance (C.KnownNat n, Backpressure a) => Backpressure (C.Vec n a) where
   boolsToBwd _ bs = C.repeat (boolsToBwd (Proxy @a) bs)
 
 instance Backpressure (CSignal dom a) where
-  boolsToBwd _ _ = pure ()
+  boolsToBwd _ _ = ()
 
 {- | Right-to-left circuit composition.
 
@@ -350,7 +350,7 @@ instance (C.KnownDomain dom) => Simulate (CSignal dom a) where
   type SimulateChannels (CSignal dom a) = 1
 
   simToSigFwd Proxy list = C.fromList_lazy list
-  simToSigBwd Proxy () = pure ()
+  simToSigBwd Proxy () = ()
   sigToSimFwd Proxy sig = C.sample_lazy sig
   sigToSimBwd Proxy _ = ()
 
@@ -368,7 +368,7 @@ instance (C.NFDataX a, C.ShowX a, Show a, C.KnownDomain dom) => Drivable (CSigna
      in Circuit (\_ -> ((), fwd1))
 
   sampleC SimulationConfig{resetCycles, ignoreReset} (Circuit f) =
-    let sampled = CE.sample_lazy (snd (f ((), pure ())))
+    let sampled = CE.sample_lazy (snd (f ((), ())))
      in if ignoreReset then drop resetCycles sampled else sampled
 
 {- | Simulate a circuit. Includes samples while reset is asserted.

clash-protocols/src/Protocols/PacketStream/Base.hs

@@ -317,7 +317,7 @@ unsafeFromCSignal ::
   Circuit
     (CSignal dom (Maybe (PacketStreamM2S dataWidth meta)))
     (PacketStream dom dataWidth meta)
-unsafeFromCSignal = Circuit (\(fwdInS, _) -> (pure (), fwdInS))
+unsafeFromCSignal = Circuit (\(fwdInS, _) -> ((), fwdInS))
 
 -- | Converts a 'PacketStream' into a 'CSignal': always acknowledges.
 toCSignal ::
@@ -359,7 +359,7 @@ unsafeAbortOnBackpressureC ::
     (CSignal dom (Maybe (PacketStreamM2S dataWidth meta)))
     (PacketStream dom dataWidth meta)
 unsafeAbortOnBackpressureC =
-  Circuit $ \(fwdInS, bwdInS) -> (pure (), go <$> bundle (fwdInS, bwdInS))
+  Circuit $ \(fwdInS, bwdInS) -> ((), go <$> bundle (fwdInS, bwdInS))
  where
   go (fwdIn, bwdIn) =
     fmap (\pkt -> pkt{_abort = _abort pkt || not (_ready bwdIn)}) fwdIn

clash-protocols/src/Protocols/Wishbone/Standard.hs

@@ -90,7 +90,7 @@ crossbarSwitch ::
 crossbarSwitch = Circuit go
  where
   go ((route, bundle -> m2ss0), bundle -> s2ms0) =
-    ((pure (), unbundle s2ms1), unbundle m2ss1)
+    (((), unbundle s2ms1), unbundle m2ss1)
    where
     m2ss1 = scatter @_ @_ @_ @_ @0 (repeat emptyWishboneM2S) <$> route <*> m2ss0
     s2ms1 = gather <$> s2ms0 <*> route

clash-protocols/tests/Tests/Protocols/Df.hs

@@ -560,7 +560,7 @@ prop_toMaybeFromMaybe =
     Df.forceResetSanity
       |> Df.toMaybe
       |> Df.unsafeFromMaybe
-      |> Circuit (first (,pure ()) . swap . first (fmap go) . first C.bundle)
+      |> Circuit (first (,()) . swap . first (fmap go) . first C.bundle)
    where
     go :: (Maybe Int, C.Unsigned 64) -> Maybe (Int, C.Unsigned 64)
     go (a, b) = liftA2 (,) a (Just b)