Compatibility with GHC-9.6

.github/workflows/master.yml

@@ -11,19 +11,20 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        cabal: ["3.6"]
+        cabal: ["3.10"]
         ghc:
           - "8.6.5"
           - "8.8.4"
           - "8.10.7"
           - "9.0.2"
-          - "9.2.7"
-          - "9.4.4"
+          - "9.2.8"
+          - "9.4.5"
+          - "9.6.2"
 
     steps:
     - uses: actions/checkout@v2
 
-    - uses: haskell/actions/setup@v1
+    - uses: haskell/actions/setup@v2
       id: setup-haskell-cabal
       name: Setup Haskell
       with:
@@ -35,7 +36,7 @@ jobs:
         cabal configure --enable-tests --enable-benchmarks --test-show-details=direct
         cabal freeze
 
-    - uses: actions/cache@v2.1.3
+    - uses: actions/cache/restore@v3
       name: Cache ~/.cabal/store and dist-newstyle
       with:
         path: |
@@ -45,9 +46,9 @@ jobs:
         restore-keys: |
           ${{ runner.os }}-${{ matrix.ghc }}-
 
-    - name: Configure
+    - name: Install doctest
       run: |
-        cabal install --ignore-project -j2 doctest --constraint='doctest ^>=0.20'
+        cabal install --ignore-project -j2 doctest --constraint='doctest ^>=0.21'
 
     - name: Build
       run: |
@@ -62,7 +63,7 @@ jobs:
         # Necessary for doctest to be found in $PATH
         export PATH="$HOME/.cabal/bin:$PATH"
 
-        DOCTEST="cabal repl --with-ghc=doctest --ghc-options=-w"
+        DOCTEST="cabal repl --with-ghc=doctest"
         (cd servant && eval $DOCTEST)
         (cd servant-client && eval $DOCTEST)
         (cd servant-client-core && eval $DOCTEST)
@@ -114,7 +115,7 @@ jobs:
     runs-on: "ubuntu-latest"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: cachix/install-nix-action@v20
       with:
         extra_nix_config: |
@@ -129,7 +130,7 @@ jobs:
         cat cabal.project
         nix-shell ghcjs.nix --run "cabal v2-update && cabal v2-freeze"
 
-    - uses: actions/cache@v2.1.3
+    - uses: actions/cache/save@v3
       name: Cache ~/.cabal/store and dist-newstyle
       with:
         path: |

cabal.project

@@ -57,3 +57,14 @@ optimization: False
 -- https://github.com/snoyberg/http-client/issues/508
 constraints: crypton < 0, crypton-connection < 0, crypton-x509 < 0, crypton-x509-store < 0, crypton-x509-system < 0, crypton-x509-validation < 0
 constraints: warp < 3.3.26
+
+allow-newer: servant-js:base
+
+-- Print ticks so that doctest type querying is consistent across GHC versions.
+-- This block can be removed when we drop support for GHC 9.4 and below.
+if(impl(ghc >= 9.6.1))
+  package servant
+    ghc-options: -fprint-redundant-promotion-ticks
+
+  package servant-server
+    ghc-options: -fprint-redundant-promotion-ticks

servant-auth/servant-auth-client/servant-auth-client.cabal

@@ -31,7 +31,7 @@ library
   default-extensions: ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
   ghc-options: -Wall
   build-depends:
-      base                >= 4.10     && < 4.18
+      base                >= 4.10     && < 4.19
     , bytestring          >= 0.10.6.0 && < 0.12
     , containers          >= 0.5.6.2  && < 0.7
     , servant-auth        == 0.4.*
@@ -71,7 +71,7 @@ test-suite spec
     , servant-auth-server  >= 0.4.2.0  && < 0.5
     , servant-server       >= 0.13     && < 0.20
     , time                 >= 1.5.0.1  && < 1.13
-    , transformers         >= 0.4.2.0  && < 0.6
+    , transformers         >= 0.4.2.0  && < 0.7
     , wai                  >= 3.2.1.2  && < 3.3
     , warp                 >= 3.2.25   && < 3.4
     , jose                 >= 0.10     && < 0.11

servant-auth/servant-auth-docs/servant-auth-docs.cabal

@@ -35,7 +35,7 @@ library
   default-extensions: ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
   ghc-options: -Wall
   build-depends:
-      base         >= 4.10    && < 4.18
+      base         >= 4.10    && < 4.19
     , servant-docs >= 0.11.2  && < 0.13
     , servant      >= 0.13    && < 0.20
     , servant-auth == 0.4.*
@@ -50,7 +50,7 @@ test-suite doctests
   build-depends:
     base,
     servant-auth-docs,
-    doctest             >= 0.16   && < 0.21,
+    doctest             >= 0.16   && < 0.22,
     QuickCheck          >= 2.11.3 && < 2.15,
     template-haskell
   ghc-options:         -Wall -threaded

servant-auth/servant-auth-server/servant-auth-server.cabal

@@ -31,7 +31,7 @@ library
   default-extensions: ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
   ghc-options: -Wall
   build-depends:
-      base                    >= 4.10     && < 4.18
+      base                    >= 4.10     && < 4.19
     , aeson                   >= 1.0.0.1  && < 3
     , base64-bytestring       >= 1.0.0.1  && < 2
     , blaze-builder           >= 0.4.1.0  && < 0.5

servant-auth/servant-auth-swagger/servant-auth-swagger.cabal

@@ -31,7 +31,7 @@ library
   default-extensions: ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
   ghc-options: -Wall
   build-depends:
-      base            >= 4.10    && < 4.18
+      base            >= 4.10    && < 4.19
     , text            >= 1.2.3.0 && < 2.1
     , servant-swagger >= 1.1.5   && < 2
     , swagger2        >= 2.2.2   && < 3

servant-auth/servant-auth/servant-auth.cabal

@@ -33,7 +33,7 @@ library
   default-extensions: ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
   ghc-options: -Wall
   build-depends:
-      base                    >= 4.10     && < 4.18
+      base                    >= 4.10     && < 4.19
     , containers              >= 0.6      && < 0.7
     , aeson                   >= 1.3.1.1  && < 3
     , jose                    >= 0.10     && < 0.11

servant-client-core/servant-client-core.cabal

@@ -50,14 +50,14 @@ library
   --
   -- note: mtl lower bound is so low because of GHC-7.8
   build-depends:
-      base                  >= 4.9      && < 4.18
+      base                  >= 4.9      && < 4.19
     , bytestring            >= 0.10.8.1 && < 0.12
     , constraints           >= 0.2      && < 0.14
     , containers            >= 0.5.7.1  && < 0.7
     , deepseq               >= 1.4.2.0  && < 1.5
     , text                  >= 1.2.3.0  && < 2.1
     , transformers          >= 0.5.2.0  && < 0.7
-    , template-haskell      >= 2.11.1.0 && < 2.20
+    , template-haskell      >= 2.11.1.0 && < 2.21
 
   if !impl(ghc >= 8.2)
     build-depends:

servant-client-core/src/Servant/Client/Core/BaseUrl.hs

@@ -57,7 +57,7 @@ instance Eq BaseUrl where
         where s ('/':x) = x
               s x       = x
 
--- | >>> traverse_ (LBS8.putStrLn . encode) $ parseBaseUrl "api.example.com"
+-- | >>> traverse_ (LBS8.putStrLn . encode) (parseBaseUrl "api.example.com" :: [BaseUrl])
 -- "http://api.example.com"
 instance ToJSON BaseUrl where
     toJSON     = toJSON . showBaseUrl
@@ -72,8 +72,8 @@ instance FromJSON BaseUrl where
 
 -- | >>> :{
 -- traverse_ (LBS8.putStrLn . encode) $ do
---   u1 <- parseBaseUrl "api.example.com"
---   u2 <- parseBaseUrl "example.com"
+--   u1 <- parseBaseUrl "api.example.com" :: [BaseUrl]
+--   u2 <- parseBaseUrl "example.com" :: [BaseUrl]
 --   return $ Map.fromList [(u1, 'x'), (u2, 'y')]
 -- :}
 -- {"http://api.example.com":"x","http://example.com":"y"}

servant-client/servant-client.cabal

@@ -41,7 +41,7 @@ library
   -- Bundled with GHC: Lower bound to not force re-installs
   -- text and mtl are bundled starting with GHC-8.4
   build-depends:
-      base                  >= 4.9      && < 4.18
+      base                  >= 4.9      && < 4.19
     , bytestring            >= 0.10.8.1 && < 0.12
     , containers            >= 0.5.7.1  && < 0.7
     , deepseq               >= 1.4.2.0  && < 1.5

servant-docs/servant-docs.cabal

@@ -41,7 +41,7 @@ library
   --
   -- note: mtl lower bound is so low because of GHC-7.8
   build-depends:
-      base       >= 4.9      && < 4.18
+      base       >= 4.9      && < 4.19
     , bytestring >= 0.10.8.1 && < 0.12
     , text       >= 1.2.3.0  && < 2.1
 
@@ -105,4 +105,4 @@ test-suite spec
       tasty         >= 1.1.0.4  && < 1.5,
       tasty-golden  >= 2.3.2    && < 2.4,
       tasty-hunit   >= 0.10.0.1 && < 0.11,
-      transformers  >= 0.5.2.0  && < 0.6
+      transformers  >= 0.5.2.0  && < 0.7

servant-foreign/servant-foreign.cabal

@@ -41,7 +41,7 @@ library
   --
   -- note: mtl lower bound is so low because of GHC-7.8
   build-depends:
-      base        >= 4.9     && < 4.18
+      base        >= 4.9     && < 4.19
     , text        >= 1.2.3.0 && < 2.1
 
   -- Servant dependencies

servant-http-streams/servant-http-streams.cabal

@@ -38,7 +38,7 @@ library
   -- Bundled with GHC: Lower bound to not force re-installs
   -- text and mtl are bundled starting with GHC-8.4
   build-depends:
-      base                  >= 4.9      && < 4.18
+      base                  >= 4.9      && < 4.19
     , bytestring            >= 0.10.8.1 && < 0.12
     , containers            >= 0.5.7.1  && < 0.7
     , deepseq               >= 1.4.2.0  && < 1.5

servant-server/servant-server.cabal

@@ -60,7 +60,7 @@ library
   -- Bundled with GHC: Lower bound to not force re-installs
   -- text and mtl are bundled starting with GHC-8.4
   build-depends:
-      base                >= 4.9      && < 4.18
+      base                >= 4.9      && < 4.19
     , bytestring          >= 0.10.8.1 && < 0.12
     , constraints         >= 0.2      && < 0.14
     , containers          >= 0.5.7.1  && < 0.7

servant-server/src/Servant/Server/Internal/Context.hs

@@ -71,7 +71,7 @@ EmptyContext .++ a = a
 --
 -- >>> getContextEntry (True :. False :. EmptyContext) :: String
 -- ...
--- ...No instance for (HasContextEntry '[] [Char])
+-- ...No instance for ...HasContextEntry '[] [Char]...
 -- ...
 class HasContextEntry (context :: [*]) (val :: *) where
     getContextEntry :: Context context -> val

servant-swagger/servant-swagger.cabal

@@ -92,7 +92,7 @@ test-suite doctests
   build-depends:
     base,
     directory >= 1.0,
-    doctest >= 0.17 && <0.21,
+    doctest >= 0.17 && <0.22,
     servant,
     QuickCheck,
     filepath

servant-swagger/src/Servant/Swagger/Internal/Test.hs

@@ -78,7 +78,7 @@ import           Servant.Swagger.Internal.TypeLevel
 -- >>> type ContactAPI = Get '[JSON] Contact
 -- >>> hspec $ validateEveryToJSON (Proxy :: Proxy ContactAPI)
 -- ...
--- ...No instance for (Arbitrary Contact)
+-- ...No instance for ...Arbitrary Contact...
 -- ...  arising from a use of ‘validateEveryToJSON’
 -- ...
 validateEveryToJSON

servant/servant.cabal

@@ -81,7 +81,7 @@ library
   --
   -- note: mtl lower bound is so low because of GHC-7.8
   build-depends:
-      base                   >= 4.9      && < 4.18
+      base                   >= 4.9      && < 4.19
     , bytestring             >= 0.10.8.1 && < 0.12
     , constraints            >= 0.2
     , mtl                    ^>= 2.2.2   || ^>= 2.3.1

servant/src/Servant/API/ResponseHeaders.hs

@@ -196,8 +196,8 @@ instance
 --
 --   1. A simple value is wrapped in "Headers '[hdr]":
 --
--- >>> let example1 = addHeader 5 "hi" :: Headers '[Header "someheader" Int] String;
--- >>> getHeaders example1
+-- >>> let example0 = addHeader 5 "hi" :: Headers '[Header "someheader" Int] String;
+-- >>> getHeaders example0
 -- [("someheader","5")]
 --
 --   2. A value that already has a header has its new header *prepended* to the

servant/src/Servant/Types/SourceT.hs

@@ -25,7 +25,7 @@ import           System.IO
 import qualified Test.QuickCheck            as QC
 
 -- $setup
--- >>> :set -XOverloadedStrings
+-- >>> import Data.String (fromString)
 -- >>> import Control.Monad.Except (runExcept)
 -- >>> import Data.Foldable (toList)
 -- >>> import qualified Data.Attoparsec.ByteString.Char8 as A8
@@ -67,7 +67,7 @@ fromStepT s = SourceT ($ s)
 instance Functor m => Functor (SourceT m) where
     fmap f = mapStepT (fmap f)
 
--- | >>> toList (source [1..10])
+-- | >>> toList (source [1::Int .. 10])
 -- [1,2,3,4,5,6,7,8,9,10]
 --
 instance Identity ~ m => Foldable (SourceT m) where
@@ -152,10 +152,14 @@ instance (Applicative m, Show1 m) => Show1 (StepT m) where
 instance (Applicative m, Show1 m, Show a) => Show (StepT m a) where
     showsPrec = showsPrec1
 
+#if !MIN_VERSION_transformers(0,6,0)
+-- Since transformers-0.6, MonadTrans only works on Monads.
+-- StepT isn't necesssarily a monad. It doesn't have the Monad instance.
+-- See https://gitlab.haskell.org/ghc/ghc/-/issues/19922
+
 -- | >>> lift [1,2,3] :: StepT [] Int
 -- Effect [Yield 1 Stop,Yield 2 Stop,Yield 3 Stop]
 --
-#if !MIN_VERSION_transformers(0,6,0)
 instance MonadTrans StepT where
     lift = Effect . fmap (`Yield` Stop)
 #endif
@@ -345,16 +349,16 @@ readFile fp =
 --
 -- >>> let parser = A.skipWhile A8.isSpace_w8 >> A.takeWhile1 A8.isDigit_w8
 --
--- >>> runExcept $ runSourceT $ transformWithAtto parser (source ["1 2 3"])
+-- >>> runExcept $ runSourceT $ transformWithAtto parser (source $ [fromString "1 2 3"])
 -- Right ["1","2","3"]
 --
--- >>> runExcept $ runSourceT $ transformWithAtto parser (source ["1", "2", "3"])
+-- >>> runExcept $ runSourceT $ transformWithAtto parser (source $ map fromString ["1", "2", "3"])
 -- Right ["123"]
 --
--- >>> runExcept $ runSourceT $ transformWithAtto parser (source ["1", "2 3", "4"])
+-- >>> runExcept $ runSourceT $ transformWithAtto parser (source $ map fromString ["1", "2 3", "4"])
 -- Right ["12","34"]
 --
--- >>> runExcept $ runSourceT $ transformWithAtto parser (source ["foobar"])
+-- >>> runExcept $ runSourceT $ transformWithAtto parser (source [fromString "foobar"])
 -- Left "Failed reading: takeWhile1"
 --
 transformWithAtto :: Monad m => A.Parser a -> SourceT m BS.ByteString -> SourceT m a