1 files changed, 22 insertions, 4 deletions

diff --git a/dht/src/Data/Tox/Msg.hs b/dht/src/Data/Tox/Msg.hs
index 8819faa7..4398586f 100644
--- a/dht/src/Data/Tox/Msg.hs
+++ b/dht/src/Data/Tox/Msg.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                        #-}
 {-# LANGUAGE DataKinds                  #-}
 {-# LANGUAGE DefaultSignatures          #-}
 {-# LANGUAGE FlexibleInstances          #-}
@@ -7,6 +8,7 @@
 {-# LANGUAGE MultiParamTypeClasses      #-}
 {-# LANGUAGE PolyKinds                  #-}
 {-# LANGUAGE StandaloneDeriving         #-}
+{-# LANGUAGE TemplateHaskell            #-}
 {-# LANGUAGE TypeFamilies               #-}
 module Data.Tox.Msg where
 
@@ -14,6 +16,7 @@ import Crypto.Error
 import qualified Crypto.PubKey.Ed25519 as Ed25519
 import Data.ByteArray             as BA
 import Data.ByteString            as B
+import Data.Constraint
 import Data.Dependent.Sum
 import Data.Functor.Contravariant
 import Data.Functor.Identity
@@ -31,6 +34,12 @@ import Crypto.Tox
 import Data.PacketBuffer (compressSequenceNumbers, decompressSequenceNumbers)
 import Network.Tox.NodeId
 
+#if MIN_VERSION_dependent_sum(0,6,0)
+import Data.Constraint.Compose
+import Data.Constraint.Extras
+import Data.Constraint.Extras.TH
+#endif
+
 newtype Unknown = Unknown B.ByteString deriving (Eq,Show)
 newtype Padded  = Padded  B.ByteString deriving (Eq,Show)
 
@@ -102,11 +111,7 @@ msgID (Pkt mid :=> Identity _) = M mid
 
 -- TODO
 instance GShow Pkt where gshowsPrec = showsPrec
-instance ShowTag Pkt Identity where
-    showTaggedPrec (Pkt _) = showsPrec
-
 instance GEq Pkt where geq (Pkt _) (Pkt _) = eqT
-instance EqTag Pkt Identity where eqTagged (Pkt _) (Pkt _) = (==)
 
 someMsgVal :: KnownMsg n => Msg n a -> SomeMsg
 someMsgVal m = msgid (proxy m)
@@ -311,3 +316,16 @@ instance Serialize Invite where
             ConfirmedInvite ns -> return () -- TODO: encode nodes.
 
 instance Packet Invite where
+
+#if MIN_VERSION_dependent_sum(0,6,0)
+-- deriveArgDict ''Pkt
+instance ArgDict (ComposeC Show Identity) Pkt where
+    type ConstraintsFor Pkt (ComposeC Show Identity) = ()
+    argDict (Pkt _) = Dict
+instance ArgDict (ComposeC Eq Identity) Pkt where
+    type ConstraintsFor Pkt (ComposeC Eq Identity) = ()
+    argDict (Pkt _) = Dict
+#else
+instance EqTag Pkt Identity where eqTagged (Pkt _) (Pkt _) = (==)
+instance ShowTag Pkt Identity where showTaggedPrec (Pkt _) = showsPrec
+#endif