Add Flat instance for CompiledCodeIn

Author: michaelpj

plutus-tx/src/PlutusTx/Code.hs

@@ -19,7 +19,7 @@ import qualified PlutusCore.Pretty       as PLC
 import qualified UntypedPlutusCore       as UPLC
 
 import           Control.Exception
-import           Flat                    (Flat, unflat)
+import           Flat                    (Flat (..), unflat)
 import           Flat.Decoder            (DecodeException)
 
 import qualified Data.ByteString         as BS
@@ -56,6 +56,16 @@ applyCode fun arg = DeserializedCode (UPLC.applyProgram (getPlc fun) (getPlc arg
 sizePlc :: (PLC.Closed uni, uni `PLC.Everywhere` Flat, Flat fun, uni `PLC.Everywhere` PLC.PrettyConst, PLC.GShow uni, PLC.Pretty fun) => CompiledCodeIn uni fun a -> Integer
 sizePlc = UPLC.programSize . getPlc
 
+instance (PLC.Closed uni, uni `PLC.Everywhere` Flat, Flat fun, uni `PLC.Everywhere` PLC.PrettyConst, PLC.GShow uni, PLC.Pretty fun)
+    => Flat (CompiledCodeIn uni fun a) where
+    encode c = encode (getPlc c)
+
+    decode = do
+        p <- decode
+        pure $ DeserializedCode p Nothing
+
+    size c = size (getPlc c)
+
 {- Note [Deserializing the AST]
 The types suggest that we can fail to deserialize the AST that we embedded in the program.
 However, we just did it ourselves, so this should be impossible, and we signal this with an