From f5f5ab01b183a419349c0195d1e4520f562c8167 Mon Sep 17 00:00:00 2001
From: t-wallet <tw.personal@tutanota.com>
Date: Wed, 24 Jul 2024 14:39:51 +0200
Subject: [PATCH 1/2] use Void typeclass instead of Default for underscored
 circuits

---
 src/Circuit.hs         | 20 ++++++++++++++++----
 src/CircuitNotation.hs |  6 +++---
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/Circuit.hs b/src/Circuit.hs
index 0d3024d..cdc8a9f 100644
--- a/src/Circuit.hs
+++ b/src/Circuit.hs
@@ -54,10 +54,22 @@ data DF (dom :: Domain)  a
 data DFM2S a = DFM2S Bool a
 newtype DFS2M = DFS2M Bool
 
-instance Default (DFM2S a) where
-  def = DFM2S False (error "error default")
-instance Default DFS2M where
-  def = DFS2M True
+-- | For /dev/null-like circuits: always acknowledge incoming data
+--   while never sending out data. Used for ignoring streams with an underscore prefix.
+class Void a where
+  driveVoid :: a
+
+instance Void () where
+  driveVoid = ()
+
+instance (Void a) => Void (Signal dom a) where
+  driveVoid = pure driveVoid
+
+instance Void (DFM2S a) where
+  driveVoid = DFM2S False (error "void")
+
+instance Void DFS2M where
+  driveVoid = DFS2M True
 
 type instance Fwd (DF dom a) = Signal dom (DFM2S a)
 type instance Bwd (DF dom a) = Signal dom DFS2M
diff --git a/src/CircuitNotation.hs b/src/CircuitNotation.hs
index 5e36429..48c5f2c 100644
--- a/src/CircuitNotation.hs
+++ b/src/CircuitNotation.hs
@@ -42,7 +42,6 @@ module CircuitNotation
 -- base
 import           Control.Exception
 import qualified Data.Data              as Data
-import           Data.Default
 import           Data.Maybe             (fromMaybe)
 #if __GLASGOW_HASKELL__ >= 900
 #else
@@ -1176,7 +1175,7 @@ completeUnderscores = do
   let addDef :: String -> PortDescription PortName -> CircuitM ()
       addDef suffix = \case
         Ref (PortName loc (unpackFS -> name@('_':_))) -> do
-          let bind = patBind (varP loc (name <> suffix)) (tagE $ varE loc (thName 'def))
+          let bind = patBind (varP loc (name <> suffix)) (tagE $ varE loc (driveVoid ?nms))
           circuitLets <>= [L loc bind]
 
         _ -> pure ()
@@ -1187,7 +1186,6 @@ completeUnderscores = do
   mapM_ addBind binds
   addBind (Binding undefined masters slaves)
 
-
 -- | Transform declarations in the module by converting circuit blocks.
 transform
     :: (?nms :: ExternalNames)
@@ -1321,6 +1319,7 @@ data ExternalNames = ExternalNames
   , fwdBwdCon :: GHC.RdrName
   , fwdAndBwdTypes :: Direction -> GHC.RdrName
   , trivialBwd :: GHC.RdrName
+  , driveVoid :: GHC.RdrName
   , consPat :: GHC.RdrName
   }
 
@@ -1335,6 +1334,7 @@ defExternalNames = ExternalNames
   , fwdAndBwdTypes = \case
       Fwd -> GHC.Unqual (OccName.mkTcOcc "Fwd")
       Bwd -> GHC.Unqual (OccName.mkTcOcc "Bwd")
+  , driveVoid = GHC.Unqual (OccName.mkVarOcc "driveVoid")
   , trivialBwd = GHC.Unqual (OccName.mkVarOcc "unitBwd")
 #if __GLASGOW_HASKELL__ > 900
   , consPat = GHC.Unqual (OccName.mkDataOcc ":>!")

From 64f566164456bf82f27461ab4d57e7fef477af6e Mon Sep 17 00:00:00 2001
From: t-wallet <tw.personal@tutanota.com>
Date: Thu, 25 Jul 2024 10:04:57 +0200
Subject: [PATCH 2/2] Change Void to DriveVoid

---
 src/Circuit.hs         | 10 +++++-----
 src/CircuitNotation.hs |  8 ++++----
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/Circuit.hs b/src/Circuit.hs
index cdc8a9f..7f9de82 100644
--- a/src/Circuit.hs
+++ b/src/Circuit.hs
@@ -56,19 +56,19 @@ newtype DFS2M = DFS2M Bool
 
 -- | For /dev/null-like circuits: always acknowledge incoming data
 --   while never sending out data. Used for ignoring streams with an underscore prefix.
-class Void a where
+class DriveVoid a where
   driveVoid :: a
 
-instance Void () where
+instance DriveVoid () where
   driveVoid = ()
 
-instance (Void a) => Void (Signal dom a) where
+instance (DriveVoid a) => DriveVoid (Signal dom a) where
   driveVoid = pure driveVoid
 
-instance Void (DFM2S a) where
+instance DriveVoid (DFM2S a) where
   driveVoid = DFM2S False (error "void")
 
-instance Void DFS2M where
+instance DriveVoid DFS2M where
   driveVoid = DFS2M True
 
 type instance Fwd (DF dom a) = Signal dom (DFM2S a)
diff --git a/src/CircuitNotation.hs b/src/CircuitNotation.hs
index 48c5f2c..9dc9254 100644
--- a/src/CircuitNotation.hs
+++ b/src/CircuitNotation.hs
@@ -1172,8 +1172,8 @@ completeUnderscores = do
   binds <- L.use circuitBinds
   masters <- L.use circuitMasters
   slaves <- L.use circuitSlaves
-  let addDef :: String -> PortDescription PortName -> CircuitM ()
-      addDef suffix = \case
+  let addVoid :: String -> PortDescription PortName -> CircuitM ()
+      addVoid suffix = \case
         Ref (PortName loc (unpackFS -> name@('_':_))) -> do
           let bind = patBind (varP loc (name <> suffix)) (tagE $ varE loc (driveVoid ?nms))
           circuitLets <>= [L loc bind]
@@ -1181,8 +1181,8 @@ completeUnderscores = do
         _ -> pure ()
       addBind :: Binding exp PortName -> CircuitM ()
       addBind (Binding _ bOut bIn) = do
-        L.traverseOf_ L.cosmos (addDef "_Fwd") bOut
-        L.traverseOf_ L.cosmos (addDef "_Bwd") bIn
+        L.traverseOf_ L.cosmos (addVoid "_Fwd") bOut
+        L.traverseOf_ L.cosmos (addVoid "_Bwd") bIn
   mapM_ addBind binds
   addBind (Binding undefined masters slaves)