Allow compilation under GHC8.

This commit makes me sad :-(

cuddle.cabal

@@ -19,8 +19,29 @@ extra-doc-files: CHANGELOG.md
 common warnings
     ghc-options: -Wall
 
+common ghc2021
+    -- These options are all on by default in GHC2021, so once we drop GHC8 we
+    -- can remove this section.
+    default-extensions:
+        DataKinds
+        DeriveGeneric
+        DeriveTraversable
+        FlexibleContexts
+        FlexibleInstances
+        GeneralizedNewtypeDeriving
+        ImportQualifiedPost
+        InstanceSigs
+        MultiParamTypeClasses
+        NamedFieldPuns
+        PolyKinds
+        RankNTypes
+        ScopedTypeVariables
+        StandaloneDeriving
+        TypeApplications
+        TypeSynonymInstances
+
 library
-    import:           warnings
+    import:           warnings, ghc2021
     exposed-modules:
         Codec.CBOR.Cuddle.CBOR.Gen
         Codec.CBOR.Cuddle.CDDL
@@ -36,7 +57,7 @@ library
 
     -- other-extensions:
     build-depends:
-        , base                ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
+        , base                ^>=4.14.3.0 || ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
         , bytestring
         , capability
         , cborg
@@ -54,31 +75,31 @@ library
         , text
 
     hs-source-dirs:   src
-    default-language: GHC2021
+    default-language: Haskell2010
 
 executable example
-    import:           warnings
-    default-language: GHC2021
+    import:           warnings, ghc2021
+    default-language: Haskell2010
     other-modules:    Conway
 
     -- other-extensions:
     hs-source-dirs:   example
     main-is:          Main.hs
     build-depends:
-        , base           ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
+        , base           ^>=4.14.3.0 || ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
         , cuddle
         , megaparsec
         , prettyprinter
         , random
         , text
 
 executable cuddle
-    import:           warnings
-    default-language: GHC2021
+    import:           warnings, ghc2021
+    default-language: Haskell2010
     hs-source-dirs:   ./bin/
     main-is:          Main.hs
     build-depends:
-        , base                  ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
+        , base                  ^>=4.14.3.0 || ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
         , cborg
         , cuddle
         , megaparsec
@@ -88,8 +109,8 @@ executable cuddle
         , text
 
 test-suite cuddle-test
-    import:           warnings
-    default-language: GHC2021
+    import:           warnings, ghc2021
+    default-language: Haskell2010
     other-modules:
         Test.Codec.CBOR.Cuddle.CDDL.Gen
         Test.Codec.CBOR.Cuddle.CDDL.Parser
@@ -100,7 +121,7 @@ test-suite cuddle-test
     hs-source-dirs:   test
     main-is:          Main.hs
     build-depends:
-        , base              ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
+        , base              ^>=4.14.3.0 || ^>=4.16.3.0 || ^>=4.18.1.0 || ^>=4.19.0.0
         , cuddle
         , hspec
         , hspec-megaparsec

src/Codec/CBOR/Cuddle/CBOR/Gen.hs

@@ -8,7 +8,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE NoFieldSelectors #-}
 {-# OPTIONS_GHC -Wno-unticked-promoted-constructors #-}
 
 -- | Generate example CBOR given a CDDL specification

src/Codec/CBOR/Cuddle/CDDL/CTree.hs

@@ -1,5 +1,4 @@
 {-# LANGUAGE DataKinds #-}
-{-# LANGUAGE NoFieldSelectors #-}
 
 module Codec.CBOR.Cuddle.CDDL.CTree where
 
@@ -53,19 +52,19 @@ traverseCTree atNode (Map xs) = Map <$> traverse atNode xs
 traverseCTree atNode (Array xs) = Array <$> traverse atNode xs
 traverseCTree atNode (Group xs) = Group <$> traverse atNode xs
 traverseCTree atNode (Choice xs) = Choice <$> traverse atNode xs
-traverseCTree atNode (KV k v cut) = do
+traverseCTree atNode (KV k v c) = do
   k' <- atNode k
   v' <- atNode v
-  pure $ KV k' v' cut
+  pure $ KV k' v' c
 traverseCTree atNode (Occur i occ) = flip Occur occ <$> atNode i
 traverseCTree atNode (Range f t inc) = do
   f' <- atNode f
   t' <- atNode t
   pure $ Range f' t' inc
-traverseCTree atNode (Control op t c) = do
+traverseCTree atNode (Control o t c) = do
   t' <- atNode t
   c' <- atNode c
-  pure $ Control op t' c'
+  pure $ Control o t' c'
 traverseCTree atNode (Enum ref) = Enum <$> atNode ref
 traverseCTree atNode (Unwrap ref) = Unwrap <$> atNode ref
 

src/Codec/CBOR/Cuddle/CDDL/Resolve.hs

@@ -1,11 +1,10 @@
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE OverloadedRecordDot #-}
+-- {-# LANGUAGE OverloadedRecordDot #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE NoFieldSelectors #-}
 
 -- | Module containing tools for 'resolving' CDDL
 --
@@ -37,7 +36,8 @@ where
 
 import Capability.Accessors (Field (..), Lift (..))
 import Capability.Error (HasThrow, MonadError (..), throw)
-import Capability.Reader (HasReader, MonadReader (..), ask, local)
+import Capability.Reader (HasReader, MonadReader (..), ask)
+import qualified Capability.Reader as Reader (local)
 import Capability.Sink (HasSink)
 import Capability.Source (HasSource)
 import Capability.State (HasState, MonadState (..), modify)
@@ -94,14 +94,14 @@ asMap (CDDL rules) = foldl' assignOrExtend Map.empty (stripComment <$> rules)
       Maybe GenericParam ->
       Maybe (Parametrised TypeOrGroup) ->
       Maybe (Parametrised TypeOrGroup)
-    extend tog _gps (Just existing) = case (existing.underlying, tog) of
+    extend tog _gps (Just existing) = case (underlying existing, tog) of
       (TOGType _, TOGType (Type0 new)) ->
         Just $
           existing
             & field @"underlying"
             % _Ctor @"TOGType"
             % _Ctor @"Type0"
-            %~ (`NE.append` new)
+            %~ (<> new)
       -- From the CDDL spec, I don't see how one is meant to extend a group.
       -- According to the description, it's meant to add a group choice, but the
       -- assignment to a group takes a 'GrpEntry', not a Group, and there is no
@@ -334,15 +334,15 @@ resolveRef env (Ref n args) = case Map.lookup n postludeBinding of
   Just pterm -> case args of
     [] -> Right . DIt $ CTree.Postlude pterm
     xs -> Left $ ArgsToPostlude pterm xs
-  Nothing -> case Map.lookup n env.global of
-    Just (parameters -> params) ->
-      if length params == length args
+  Nothing -> case Map.lookup n (global env) of
+    Just (parameters -> params') ->
+      if length params' == length args
         then
-          let localBinds = Map.fromList $ zip params args
+          let localBinds = Map.fromList $ zip params' args
               newEnv = env & field @"local" %~ Map.union localBinds
            in RuleRef n <$> traverse (resolveRef newEnv) args
-        else Left $ MismatchingArgs n params
-    Nothing -> case Map.lookup n env.local of
+        else Left $ MismatchingArgs n params'
+    Nothing -> case Map.lookup n (local env) of
       Just _ -> Right $ GenericRef n
       Nothing -> Left $ UnboundReference n
 
@@ -460,14 +460,14 @@ synthMono n@(Name origName) args =
         globalBinds <- ask @"global"
         case Map.lookup n globalBinds of
           Just (Unparametrised _) -> throwNR $ MismatchingArgs n []
-          Just (Parametrised r params) ->
-            if length params == length args
+          Just (Parametrised r params') ->
+            if length params' == length args
               then
-                let localBinds = Map.fromList $ zip params args
-                 in local @"local" (Map.union localBinds) $ do
+                let localBinds = Map.fromList $ zip params' args
+                 in Reader.local @"local" (Map.union localBinds) $ do
                       foo <- resolveGenericRef r
                       modify @"synth" $ Map.insert fresh foo
-              else throwNR $ MismatchingArgs n params
+              else throwNR $ MismatchingArgs n params'
           Nothing -> throwNR $ UnboundReference n
         pure fresh
 
@@ -508,7 +508,7 @@ buildMonoCTree ::
   CTreeRoot DistRef ->
   Either NameResolutionFailure (CTreeRoot' Identity MonoRef)
 buildMonoCTree (CTreeRoot ct) = do
-  let a1 = runExceptT (monoCTree monoC).runMonoM
+  let a1 = runExceptT $ runMonoM (monoCTree monoC)
       a2 = runStateT a1 mempty
       (er, newBindings) = runReader a2 initBindingEnv
   CTreeRoot r <- er