From 4627683a647395f44443fa66d7e92a79eb98cab8 Mon Sep 17 00:00:00 2001
From: Teo Camarasu <teofilcamarasu@gmail.com>
Date: Tue, 9 Aug 2022 11:05:00 +0100
Subject: [PATCH] Fix TypeError for GHC-9.4

In GHC-9.4 the typechecker changed requiring more annotations in positions like this. See https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.4#ambiguous-types-containing-a-typeerror and https://gitlab.haskell.org/ghc/ghc/-/issues/21149
---
 servant-server/src/Servant/Server/Internal.hs | 6 ++++--
 servant/src/Servant/Links.hs                  | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/servant-server/src/Servant/Server/Internal.hs b/servant-server/src/Servant/Server/Internal.hs
index a2b4f033..77978d64 100644
--- a/servant-server/src/Servant/Server/Internal.hs
+++ b/servant-server/src/Servant/Server/Internal.hs
@@ -94,6 +94,8 @@ import           Servant.API.TypeErrors
 import           Web.HttpApiData
                  (FromHttpApiData, parseHeader, parseQueryParam, parseUrlPiece,
                  parseUrlPieces)
+import           Data.Kind
+                 (Type)
 
 import           Servant.Server.Internal.BasicAuth
 import           Servant.Server.Internal.Context
@@ -821,7 +823,7 @@ instance (HasContextEntry context (NamedContext name subContext), HasServer subA
 -------------------------------------------------------------------------------
 
 -- Erroring instance for 'HasServer' when a combinator is not fully applied
-instance TypeError (PartialApplication HasServer arr) => HasServer ((arr :: a -> b) :> sub) context
+instance TypeError (PartialApplication @(Type -> [Type] -> Constraint) HasServer arr) => HasServer ((arr :: a -> b) :> sub) context
   where
     type ServerT (arr :> sub) _ = TypeError (PartialApplication (HasServer :: * -> [*] -> Constraint) arr)
     route = error "unreachable"
@@ -865,7 +867,7 @@ type HasServerArrowTypeError a b =
 -- XXX: This omits the @context@ parameter, e.g.:
 --
 -- "There is no instance for HasServer (Bool :> …)". Do we care ?
-instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub HasServer ty) => HasServer (ty :> sub) context
+instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub @(Type -> [Type] -> Constraint) HasServer ty) => HasServer (ty :> sub) context
 
 instance {-# OVERLAPPABLE #-} TypeError (NoInstanceFor (HasServer api context)) => HasServer api context
 
diff --git a/servant/src/Servant/Links.hs b/servant/src/Servant/Links.hs
index ce07e22d..9074429b 100644
--- a/servant/src/Servant/Links.hs
+++ b/servant/src/Servant/Links.hs
@@ -193,6 +193,8 @@ import           Servant.API.Verbs
 import           Servant.API.WithNamedContext
                  (WithNamedContext)
 import           Web.HttpApiData
+import           Data.Kind
+                 (Type)
 
 -- | A safe link datatype.
 -- The only way of constructing a 'Link' is using 'safeLink', which means any
@@ -647,12 +649,12 @@ simpleToLink _ toA _ = toLink toA (Proxy :: Proxy sub)
 -- >>> import Data.Text (Text)
 
 -- Erroring instance for 'HasLink' when a combinator is not fully applied
-instance TypeError (PartialApplication HasLink arr) => HasLink ((arr :: a -> b) :> sub)
+instance TypeError (PartialApplication @(Type -> Constraint) HasLink arr) => HasLink ((arr :: a -> b) :> sub)
   where
     type MkLink (arr :> sub) _ = TypeError (PartialApplication (HasLink :: * -> Constraint) arr)
     toLink = error "unreachable"
 
 -- Erroring instances for 'HasLink' for unknown API combinators
-instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub HasLink ty) => HasLink (ty :> sub)
+instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub @(Type -> Constraint) HasLink ty) => HasLink (ty :> sub)
 
 instance {-# OVERLAPPABLE #-} TypeError (NoInstanceFor (HasLink api)) => HasLink api