Drop GHC 8.10 (#1489)

The node already uses 9.6, so we can finally drop 8.10 and get rid of a
lot of cruft.

I tried to remove everything I could find by grepping for a few ad-hoc
regexes; maybe there is more, but we can remove that as we go.

Follow-up work (like upgrading from `Haskell2010` to `GHC2021`) can
happen in later PRs as it needs more discussion.

Author: amesgen

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ["8.10.7", "9.6.6", "9.10.1", "9.12"]
+        ghc: ["9.6.6", "9.10.1", "9.12"]
         variant: [default, no-thunks]
         test-set: [all, no-thunks-safe]
         exclude:
@@ -193,7 +193,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ["8.10.7", "9.6.6", "9.10.1"]
+        ghc: ["9.6.6", "9.10.1"]
 
     steps:
     - uses: actions/checkout@v4

nix/ci.nix

@@ -42,11 +42,6 @@ let
       formattingLinting = import ./formatting-linting.nix pkgs;
       inherit (pkgs) consensus-pdfs agda-spec;
 
-      # ensure we can still build on 8.10, can be removed soon
-      haskell810 = builtins.removeAttrs
-        (mkHaskellJobsFor pkgs.hsPkgs.projectVariants.ghc810)
-        [ "checks" "devShell" "devShellProfiled" ];
-
       # also already test GHC 9.10, but only on Linux to reduce CI load
       haskell910 = mkHaskellJobsFor pkgs.hsPkgs.projectVariants.ghc910;
     };

nix/haskell.nix

@@ -16,7 +16,6 @@ let
     src = ./..;
     compiler-nix-name = "ghc966";
     flake.variants = {
-      ghc810 = { compiler-nix-name = lib.mkForce "ghc8107"; };
       ghc910 = { compiler-nix-name = lib.mkForce "ghc9101"; };
     };
     inputMap = {

ouroboros-consensus-cardano/changelog.d/20250430_141707_alexander.esgen_drop_ghc810.md

@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Drop GHC 8.10 support.

ouroboros-consensus-cardano/ouroboros-consensus-cardano.cabal

@@ -171,9 +171,6 @@ library
     validation,
     vector-map,
 
-  -- GHC 8.10.7 on aarch64-darwin cannot use text-2
-  build-depends: text >=1.2.5.0 && <2.2
-
 library unstable-byronspec
   import: common-lib
   visibility: public

ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Ledger.hs

@@ -20,13 +20,6 @@
 -- TODO: can we un-orphan this module?
 {-# OPTIONS_GHC -Wno-orphans #-}
 
-#if __GLASGOW_HASKELL__ <= 906
-{-# OPTIONS_GHC -Wno-incomplete-patterns
-                -Wno-incomplete-uni-patterns
-                -Wno-incomplete-record-updates
-                -Wno-overlapping-patterns #-}
-#endif
-
 module Ouroboros.Consensus.Cardano.Ledger (
     CardanoTxOut (..)
   , eliminateCardanoTxOut

ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Node.hs

@@ -17,21 +17,6 @@
 
 {-# OPTIONS_GHC -Wno-orphans #-}
 
--- Disable completeness checks on GHC versions pre-9.6, where this can be
--- exceptionally slow:
-#if __GLASGOW_HASKELL__ <= 906
-{-# OPTIONS_GHC -Wno-incomplete-patterns
-                -Wno-incomplete-uni-patterns
-                -Wno-incomplete-record-updates
-                -Wno-overlapping-patterns #-}
-#endif
-
--- TODO: this is required for ghc-8.10.7, because using NamedFieldPuns and
--- PatternSynonyms with record syntax results in warnings related to shadowing.
--- This can be removed once we drop ghc-8.10.7.
-
-{-# OPTIONS_GHC -Wno-name-shadowing #-}
-
 module Ouroboros.Consensus.Cardano.Node (
     CardanoHardForkConstraints
   , CardanoHardForkTrigger (..)
@@ -831,10 +816,10 @@ protocolInfoCardano paramsCardano
              ShelleyBasedEra era
           => WrapTransitionConfig (ShelleyBlock proto era)
           -> (Flip LedgerState ValuesMK -.-> Flip LedgerState ValuesMK) (ShelleyBlock proto era)
-        injectIntoTestState (WrapTransitionConfig cfg) = fn $ \(Flip st) ->
+        injectIntoTestState (WrapTransitionConfig tcfg) = fn $ \(Flip st) ->
           -- We need to unstow the injected values
           Flip $ unstowLedgerTables $ forgetLedgerTables $ st {
-            Shelley.shelleyLedgerState = L.injectIntoTestState cfg
+            Shelley.shelleyLedgerState = L.injectIntoTestState tcfg
               (Shelley.shelleyLedgerState $ stowLedgerTables st)
           }
 

ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/QueryHF.hs

@@ -17,12 +17,6 @@
 {-# LANGUAGE UndecidableSuperClasses #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
-#if __GLASGOW_HASKELL__ <= 906
-{-# OPTIONS_GHC -Wno-incomplete-patterns
-                -Wno-incomplete-uni-patterns
-                -Wno-incomplete-record-updates
-                -Wno-overlapping-patterns #-}
-#endif
 
 module Ouroboros.Consensus.Cardano.QueryHF () where
 

ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Ledger/Ledger.hs

@@ -21,12 +21,6 @@
 {-# LANGUAGE UndecidableInstances #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
-#if __GLASGOW_HASKELL__ <= 906
-{-# OPTIONS_GHC -Wno-incomplete-patterns
-                -Wno-incomplete-uni-patterns
-                -Wno-incomplete-record-updates
-                -Wno-overlapping-patterns #-}
-#endif
 
 module Ouroboros.Consensus.Shelley.Ledger.Ledger (
     LedgerState (..)

ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Ledger/Query.hs

@@ -20,12 +20,6 @@
 {-# LANGUAGE UndecidableInstances #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
-#if __GLASGOW_HASKELL__ <= 906
-{-# OPTIONS_GHC -Wno-incomplete-patterns
-                -Wno-incomplete-uni-patterns
-                -Wno-incomplete-record-updates
-                -Wno-overlapping-patterns #-}
-#endif
 
 module Ouroboros.Consensus.Shelley.Ledger.Query (
     BlockQuery (..)

ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Protocol/Praos.hs

@@ -4,10 +4,6 @@
 {-# LANGUAGE TypeFamilies #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
--- See https://gitlab.haskell.org/ghc/ghc/-/issues/14630. GHC currently warns
--- (erroneously) about name shadowing for record field selectors defined by
--- pattern synonyms. This can be deleted once GHC 8.10.7 is gone.
-{-# OPTIONS_GHC -Wno-name-shadowing #-}
 
 module Ouroboros.Consensus.Shelley.Protocol.Praos (PraosEnvelopeError (..)) where
 

ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Tools/DBAnalyser/Analysis.hs

@@ -371,9 +371,7 @@ showEBBs AnalysisEnv { db, registry, startFrom, limit, tracer } = do
 storeLedgerStateAt ::
      forall blk .
      ( LedgerSupportsProtocol blk
-#if __GLASGOW_HASKELL__ > 810
      , HasAnalysis blk
-#endif
      )
   => SlotNo
   -> LedgerApplicationMode

ouroboros-consensus-diffusion/changelog.d/20250430_141654_alexander.esgen_drop_ghc810.md

@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Drop GHC 8.10 support.

ouroboros-consensus-diffusion/ouroboros-consensus-diffusion.cabal

@@ -107,9 +107,6 @@ library
     typed-protocols,
     typed-protocols-stateful,
 
-  -- GHC 8.10.7 on aarch64-darwin cannot use text-2
-  build-depends: text >=1.2.5.0 && <2.2
-
 library unstable-diffusion-testlib
   import: common-lib
   visibility: public

ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/Genesis/Setup/Classifiers.hs

@@ -21,7 +21,7 @@ import qualified Data.List.NonEmpty as NonEmpty
 import qualified Data.Map as Map
 import           Data.Maybe (mapMaybe)
 import           Data.Word (Word64)
-import           Ouroboros.Consensus.Block (ChainHash (BlockHash), HeaderHash,
+import           Ouroboros.Consensus.Block (ChainHash (..), HeaderHash,
                      blockSlot, succWithOrigin)
 import           Ouroboros.Consensus.Block.Abstract (SlotNo (SlotNo),
                      withOrigin)
@@ -269,6 +269,4 @@ simpleHash ::
   [Word64]
 simpleHash = \case
   BlockHash (TestHash h) -> reverse (NonEmpty.toList h)
-  -- not matching on @GenesisHash@ because 8.10 can't prove exhaustiveness of
-  -- TestHash with the equality constraint
-  _ -> []
+  GenesisHash            -> []

ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/PointSchedule/Shrinking/Tests.hs

@@ -8,6 +8,7 @@ module Test.Consensus.PointSchedule.Shrinking.Tests (tests) where
 import           Data.Foldable (toList)
 import           Data.Map (keys)
 import           Data.Maybe (mapMaybe)
+import           Ouroboros.Consensus.Util (lastMaybe)
 import           Test.Consensus.Genesis.Setup (genChains)
 import           Test.Consensus.Genesis.Tests.Uniform (genUniformSchedulePoints)
 import           Test.Consensus.PointSchedule (PeerSchedule, PointSchedule (..),
@@ -35,12 +36,6 @@ prop_shortens = checkShrinkProperty isShorterThan
 prop_preservesFinalStates :: Property
 prop_preservesFinalStates = checkShrinkProperty doesNotChangeFinalState
 
--- | Apparently, `unsnoc` hasn't been invented yet, so we'll do this manually
-lastM :: [a] -> Maybe a
-lastM []     = Nothing
-lastM [a]    = Just a
-lastM (_:ps) = lastM ps
-
 samePeers :: Peers (PeerSchedule blk) -> Peers (PeerSchedule blk) -> Bool
 samePeers sch1 sch2 =
   (keys $ adversarialPeers sch1)
@@ -53,7 +48,7 @@ isShorterThan :: Peers (PeerSchedule blk) -> Peers (PeerSchedule blk) -> Bool
 isShorterThan original shrunk =
   samePeers original shrunk
   && (or $ zipWith
-    (\oldSch newSch -> (fst <$> lastM newSch) < (fst <$> lastM oldSch))
+    (\oldSch newSch -> (fst <$> lastMaybe newSch) < (fst <$> lastMaybe oldSch))
     (toList original)
     (toList shrunk)
   )
@@ -72,11 +67,11 @@ doesNotChangeFinalState original shrunk =
   )
   where
     lastTP :: PeerSchedule blk -> Maybe (SchedulePoint blk)
-    lastTP sch = lastM $ mapMaybe (\case (_, p@(ScheduleTipPoint    _)) -> Just p ; _ -> Nothing) sch
+    lastTP sch = lastMaybe $ mapMaybe (\case (_, p@(ScheduleTipPoint    _)) -> Just p ; _ -> Nothing) sch
     lastHP :: PeerSchedule blk -> Maybe (SchedulePoint blk)
-    lastHP sch = lastM $ mapMaybe (\case (_, p@(ScheduleHeaderPoint _)) -> Just p ; _ -> Nothing) sch
+    lastHP sch = lastMaybe $ mapMaybe (\case (_, p@(ScheduleHeaderPoint _)) -> Just p ; _ -> Nothing) sch
     lastBP :: PeerSchedule blk -> Maybe (SchedulePoint blk)
-    lastBP sch = lastM $ mapMaybe (\case (_, p@(ScheduleBlockPoint  _)) -> Just p ; _ -> Nothing) sch
+    lastBP sch = lastMaybe $ mapMaybe (\case (_, p@(ScheduleBlockPoint  _)) -> Just p ; _ -> Nothing) sch
 
 checkShrinkProperty :: (Peers (PeerSchedule TestBlock) -> Peers (PeerSchedule TestBlock) -> Bool) -> Property
 checkShrinkProperty prop =

ouroboros-consensus/changelog.d/20250430_141645_alexander.esgen_drop_ghc810.md

@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Drop GHC 8.10 support.

ouroboros-consensus/ouroboros-consensus.cabal

@@ -61,8 +61,7 @@ common common-bench
   -- We use this option to avoid skewed results due to changes in cache-line
   -- alignment. See
   -- https://github.com/Bodigrim/tasty-bench#comparison-against-baseline
-  if impl(ghc >=8.6)
-    ghc-options: -fproc-alignment=64
+  ghc-options: -fproc-alignment=64
 
 library
   import: common-lib
@@ -356,10 +355,6 @@ library
     typed-protocols ^>=0.3,
     vector ^>=0.13,
 
-  if !impl(ghc >=9.4)
-    build-depends: data-array-byte
-  -- GHC 8.10.7 on aarch64-darwin cannot use text-2
-  build-depends: text >=1.2.5.0 && <2.2
   x-docspec-extra-packages:
     directory
     latex-svg-image