Replace ConwayNewEpochPredFailure with Void.

Replace the corresponding check with an assertion.

Author: aniketd

eras/conway/impl/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## 1.20.0.0
 
+- Remove `ConwayNewEpochPredFailure` and replace it with `Void`. #5007
 * Remove `ConwayTxBody`
 * Removed `era` parameter from `ConwayTxBodyRaw`
 * Add `MkConwayTxBody` and all members of `ConwayTxBodyRaw`:

eras/conway/impl/src/Cardano/Ledger/Conway/Rules/NewEpoch.hs

@@ -17,7 +17,6 @@
 
 module Cardano.Ledger.Conway.Rules.NewEpoch (
   ConwayNEWEPOCH,
-  ConwayNewEpochPredFailure (..),
   ConwayNewEpochEvent (..),
 ) where
 
@@ -54,28 +53,15 @@ import Cardano.Ledger.Slot (EpochNo (EpochNo))
 import Cardano.Ledger.State
 import qualified Cardano.Ledger.Val as Val
 import Control.DeepSeq (NFData)
+import Control.Exception (assert)
 import Control.State.Transition
 import Data.Default (Default (..))
 import qualified Data.Map.Strict as Map
 import Data.Set (Set)
+import Data.Void (Void)
 import GHC.Generics (Generic)
 import Lens.Micro ((%~), (&), (^.))
 
-newtype ConwayNewEpochPredFailure era
-  = CorruptRewardUpdate
-      RewardUpdate -- The reward update which violates an invariant
-  deriving (Generic)
-
-deriving instance Eq (ConwayNewEpochPredFailure era)
-
-deriving instance
-  ( Show (PredicateFailure (EraRule "EPOCH" era))
-  , Show (PredicateFailure (EraRule "RATIFY" era))
-  ) =>
-  Show (ConwayNewEpochPredFailure era)
-
-instance NFData (ConwayNewEpochPredFailure era)
-
 data ConwayNewEpochEvent era
   = DeltaRewardEvent !(Event (EraRule "RUPD" era))
   | RestrainedRewards
@@ -121,14 +107,16 @@ instance
   , GovState era ~ ConwayGovState era
   , Eq (PredicateFailure (EraRule "RATIFY" era))
   , Show (PredicateFailure (EraRule "RATIFY" era))
+  , Eq (PredicateFailure (ConwayNEWEPOCH era))
+  , Show (PredicateFailure (ConwayNEWEPOCH era))
   ) =>
   STS (ConwayNEWEPOCH era)
   where
   type State (ConwayNEWEPOCH era) = NewEpochState era
   type Signal (ConwayNEWEPOCH era) = EpochNo
   type Environment (ConwayNEWEPOCH era) = ()
   type BaseM (ConwayNEWEPOCH era) = ShelleyBase
-  type PredicateFailure (ConwayNEWEPOCH era) = ConwayNewEpochPredFailure era
+  type PredicateFailure (ConwayNEWEPOCH era) = Void
   type Event (ConwayNEWEPOCH era) = ConwayNewEpochEvent era
 
   initialRules =
@@ -162,6 +150,8 @@ newEpochTransition ::
   , GovState era ~ ConwayGovState era
   , Eq (PredicateFailure (EraRule "RATIFY" era))
   , Show (PredicateFailure (EraRule "RATIFY" era))
+  , Eq (PredicateFailure (ConwayNEWEPOCH era))
+  , Show (PredicateFailure (ConwayNEWEPOCH era))
   ) =>
   TransitionRule (ConwayNEWEPOCH era)
 newEpochTransition = do
@@ -216,7 +206,7 @@ updateRewards ::
   Rule (ConwayNEWEPOCH era) 'Transition (EpochState era)
 updateRewards es e ru'@(RewardUpdate dt dr rs_ df _) = do
   let totRs = sumRewards (es ^. prevPParamsEpochStateL . ppProtocolVersionL) rs_
-  Val.isZero (dt <> dr <> toDeltaCoin totRs <> df) ?! CorruptRewardUpdate ru'
+   in assert (Val.isZero (dt <> dr <> toDeltaCoin totRs <> df)) (pure ())
   let !(!es', filtered) = applyRUpdFiltered ru' es
   tellEvent $ RestrainedRewards e (frShelleyIgnored filtered) (frUnregistered filtered)
   -- This event (which is only generated once per epoch) must be generated even if the
@@ -226,8 +216,8 @@ updateRewards es e ru'@(RewardUpdate dt dr rs_ df _) = do
 
 instance
   ( STS (ConwayNEWEPOCH era)
-  , PredicateFailure (EraRule "NEWEPOCH" era) ~ ConwayNewEpochPredFailure era
   , Event (EraRule "NEWEPOCH" era) ~ ConwayNewEpochEvent era
+  , PredicateFailure (EraRule "NEWEPOCH" era) ~ PredicateFailure (ConwayNEWEPOCH era)
   ) =>
   Embed (ConwayNEWEPOCH era) (ShelleyTICK era)
   where

eras/conway/impl/testlib/Test/Cardano/Ledger/Conway/TreeDiff.hs

@@ -281,8 +281,6 @@ instance ToExpr (PParamsHKD StrictMaybe era) => ToExpr (RatifySignal era)
 
 instance ToExpr (PParamsHKD StrictMaybe era) => ToExpr (EnactSignal era)
 
-instance ToExpr (ConwayNewEpochPredFailure era)
-
 instance
   ( ToExpr (PParamsHKD Identity era)
   , ToExpr (PParamsHKD StrictMaybe era)

libs/cardano-ledger-conformance/src/Test/Cardano/Ledger/Conformance/SpecTranslate/Conway/Cert.hs

@@ -223,7 +223,3 @@ instance
       <$> toSpecRep nesEL
       <*> toSpecRep nesEs
       <*> toSpecRep nesRu
-
-instance SpecTranslate ctx (ConwayNewEpochPredFailure era) where
-  type SpecRep (ConwayNewEpochPredFailure era) = OpaqueErrorString
-  toSpecRep = pure . showOpaqueErrorString

libs/cardano-ledger-test/src/Test/Cardano/Ledger/Generic/PrettyCore.hs

@@ -134,7 +134,6 @@ import Cardano.Ledger.Conway.Rules (
   ConwayGovCertPredFailure (..),
   ConwayGovPredFailure (..),
   ConwayLedgerPredFailure (..),
-  ConwayNewEpochPredFailure,
   ConwayUtxosPredFailure,
   EnactSignal (..),
   GovEnv (..),
@@ -1265,7 +1264,7 @@ ppNEWEPOCH Allegra x = ppShelleyNewEpochPredicateFailure x
 ppNEWEPOCH Mary x = ppShelleyNewEpochPredicateFailure x
 ppNEWEPOCH Alonzo x = ppShelleyNewEpochPredicateFailure x
 ppNEWEPOCH Babbage x = ppShelleyNewEpochPredicateFailure x
-ppNEWEPOCH Conway x = ppConwayNewEpochPredFailure x
+ppNEWEPOCH Conway x = absurd x
 
 ppEPOCH :: Proof era -> PredicateFailure (EraRule "EPOCH" era) -> PDoc
 ppEPOCH Shelley x = ppShelleyEpochPredFailure x
@@ -1710,13 +1709,6 @@ ppShelleyNewEpochPredicateFailure (MirFailure _) =
 instance Reflect era => PrettyA (ShelleyNewEpochPredFailure era) where
   prettyA = ppShelleyNewEpochPredicateFailure
 
-ppConwayNewEpochPredFailure :: ConwayNewEpochPredFailure era -> PDoc
-ppConwayNewEpochPredFailure (ConwayRules.CorruptRewardUpdate x) =
-  ppSexp "CorruptRewardUpdate" [ppRewardUpdate x]
-
-instance PrettyA (ConwayNewEpochPredFailure era) where
-  prettyA = ppConwayNewEpochPredFailure
-
 -- ===============
 
 ppShelleyEpochPredFailure :: forall era. ShelleyEpochPredFailure era -> PDoc