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Move erroring instances of HasServer to separate file
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+95
-66
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4 files changed

+95
-66
lines changed

‎servant-server/servant-server.cabal

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@@ -51,6 +51,7 @@ library
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Servant.Server.Internal.RoutingApplication
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Servant.Server.Internal.ServerError
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Servant.Server.StaticFiles
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Servant.Server.TypeErrors
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Servant.Server.UVerb
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-- deprecated

‎servant-server/src/Servant/Server.hs

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@@ -126,6 +126,7 @@ import Data.Text
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import Network.Wai
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(Application)
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import Servant.Server.Internal
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import Servant.Server.TypeErrors ()
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import Servant.Server.UVerb
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‎servant-server/src/Servant/Server/Internal.hs

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@@ -42,7 +42,7 @@ import qualified Data.ByteString as B
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import qualified Data.ByteString.Builder as BB
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import qualified Data.ByteString.Char8 as BC8
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import qualified Data.ByteString.Lazy as BL
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import Data.Constraint (Constraint, Dict(..))
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import Data.Constraint (Dict(..))
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import Data.Either
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(partitionEithers)
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import Data.Maybe
@@ -57,7 +57,7 @@ import qualified Data.Text as T
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import Data.Typeable
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import GHC.Generics
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import GHC.TypeLits
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(KnownNat, KnownSymbol, TypeError, symbolVal)
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(KnownNat, KnownSymbol, symbolVal)
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import qualified Network.HTTP.Media as NHM
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import Network.HTTP.Types hiding
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(Header, ResponseHeaders)
@@ -91,7 +91,6 @@ import Servant.API.ResponseHeaders
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import Servant.API.Status
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(statusFromNat)
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import qualified Servant.Types.SourceT as S
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import Servant.API.TypeErrors
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import Web.HttpApiData
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(FromHttpApiData, parseHeader, parseQueryParam, parseUrlPiece,
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parseUrlPieces)
@@ -107,8 +106,6 @@ import Servant.Server.Internal.RouteResult
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import Servant.Server.Internal.RoutingApplication
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import Servant.Server.Internal.ServerError
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import GHC.TypeLits
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(ErrorMessage (..))
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import Servant.API.TypeLevel
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(AtLeastOneFragment, FragmentUnique)
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@@ -817,67 +814,6 @@ instance (HasContextEntry context (NamedContext name subContext), HasServer subA
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hoistServerWithContext _ _ nt s = hoistServerWithContext (Proxy :: Proxy subApi) (Proxy :: Proxy subContext) nt s
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-------------------------------------------------------------------------------
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-- Custom type errors
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-------------------------------------------------------------------------------
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-- Erroring instance for 'HasServer' when a combinator is not fully applied
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instance TypeError (PartialApplication
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#if __GLASGOW_HASKELL__ >= 904
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@(Type -> [Type] -> Constraint)
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#endif
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HasServer arr) => HasServer ((arr :: a -> b) :> sub) context
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where
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type ServerT (arr :> sub) _ = TypeError (PartialApplication (HasServer :: * -> [*] -> Constraint) arr)
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route = error "unreachable"
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hoistServerWithContext _ _ _ _ = error "unreachable"
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-- | This instance prevents from accidentally using '->' instead of ':>'
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--
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-- >>> serve (Proxy :: Proxy (Capture "foo" Int -> Get '[JSON] Int)) (error "...")
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-- ...
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-- ...No instance HasServer (a -> b).
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-- ...Maybe you have used '->' instead of ':>' between
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-- ...Capture' '[] "foo" Int
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-- ...and
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-- ...Verb 'GET 200 '[JSON] Int
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-- ...
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--
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-- >>> undefined :: Server (Capture "foo" Int -> Get '[JSON] Int)
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-- ...
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-- ...No instance HasServer (a -> b).
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-- ...Maybe you have used '->' instead of ':>' between
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-- ...Capture' '[] "foo" Int
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-- ...and
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-- ...Verb 'GET 200 '[JSON] Int
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-- ...
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--
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instance TypeError (HasServerArrowTypeError a b) => HasServer (a -> b) context
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where
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type ServerT (a -> b) m = TypeError (HasServerArrowTypeError a b)
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route _ _ _ = error "servant-server panic: impossible happened in HasServer (a -> b)"
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hoistServerWithContext _ _ _ = id
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type HasServerArrowTypeError a b =
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'Text "No instance HasServer (a -> b)."
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':$$: 'Text "Maybe you have used '->' instead of ':>' between "
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':$$: 'ShowType a
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':$$: 'Text "and"
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':$$: 'ShowType b
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-- Erroring instances for 'HasServer' for unknown API combinators
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-- XXX: This omits the @context@ parameter, e.g.:
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--
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-- "There is no instance for HasServer (Bool :> …)". Do we care ?
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instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub
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#if __GLASGOW_HASKELL__ >= 904
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@(Type -> [Type] -> Constraint)
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#endif
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HasServer ty) => HasServer (ty :> sub) context
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instance {-# OVERLAPPABLE #-} TypeError (NoInstanceFor (HasServer api context)) => HasServer api context
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-- | Ignore @'Fragment'@ in server handlers.
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-- See <https://ietf.org/rfc/rfc2616.html#section-15.1.3> for more details.
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--

‎servant-server/src/Servant/Server/TypeErrors.hs

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@@ -0,0 +1,91 @@
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{-# LANGUAGE AllowAmbiguousTypes #-}
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{-# LANGUAGE CPP #-}
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{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE MultiParamTypeClasses #-}
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{-# LANGUAGE PolyKinds #-}
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{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE TypeOperators #-}
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{-# LANGUAGE UndecidableInstances #-}
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{-# OPTIONS_GHC -fno-warn-orphans #-}
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{-# OPTIONS_GHC -fno-warn-missing-methods #-}
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-- | This module contains erroring instances for @Servant.Server.Internal@.
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-- They are separated from the bulk of the code, because they raise "missing methods"
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-- warnings. These warnings are expected, but ignoring them would lead to missing
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-- relevant warnings in @SServant.Server.Internal@. Therefore, we put them in a separate
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-- file, and ignore the warnings here.
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module Servant.Server.TypeErrors ()
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where
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import Data.Constraint (Constraint)
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import GHC.TypeLits
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(TypeError)
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import Prelude ()
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import Prelude.Compat
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import Servant.API
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((:>))
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import Servant.API.TypeErrors
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import Servant.Server.Internal
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import GHC.TypeLits
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(ErrorMessage (..))
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-- Erroring instance for 'HasServer' when a combinator is not fully applied
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instance TypeError (PartialApplication
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#if __GLASGOW_HASKELL__ >= 904
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@(Type -> [Type] -> Constraint)
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#endif
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HasServer arr) => HasServer ((arr :: a -> b) :> sub) context
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where
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type ServerT (arr :> sub) _ = TypeError (PartialApplication (HasServer :: * -> [*] -> Constraint) arr)
44+
route = error "unreachable"
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hoistServerWithContext _ _ _ _ = error "unreachable"
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47+
-- | This instance prevents from accidentally using '->' instead of ':>'
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--
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-- >>> serve (Proxy :: Proxy (Capture "foo" Int -> Get '[JSON] Int)) (error "...")
50+
-- ...
51+
-- ...No instance HasServer (a -> b).
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-- ...Maybe you have used '->' instead of ':>' between
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-- ...Capture' '[] "foo" Int
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-- ...and
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-- ...Verb 'GET 200 '[JSON] Int
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-- ...
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--
58+
-- >>> undefined :: Server (Capture "foo" Int -> Get '[JSON] Int)
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-- ...
60+
-- ...No instance HasServer (a -> b).
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-- ...Maybe you have used '->' instead of ':>' between
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-- ...Capture' '[] "foo" Int
63+
-- ...and
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-- ...Verb 'GET 200 '[JSON] Int
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-- ...
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--
67+
instance TypeError (HasServerArrowTypeError a b) => HasServer (a -> b) context
68+
where
69+
type ServerT (a -> b) m = TypeError (HasServerArrowTypeError a b)
70+
route _ _ _ = error "servant-server panic: impossible happened in HasServer (a -> b)"
71+
hoistServerWithContext _ _ _ = id
72+
73+
type HasServerArrowTypeError a b =
74+
'Text "No instance HasServer (a -> b)."
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':$$: 'Text "Maybe you have used '->' instead of ':>' between "
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':$$: 'ShowType a
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':$$: 'Text "and"
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':$$: 'ShowType b
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80+
-- Erroring instances for 'HasServer' for unknown API combinators
81+
82+
-- XXX: This omits the @context@ parameter, e.g.:
83+
--
84+
-- "There is no instance for HasServer (Bool :> …)". Do we care ?
85+
instance {-# OVERLAPPABLE #-} TypeError (NoInstanceForSub
86+
#if __GLASGOW_HASKELL__ >= 904
87+
@(Type -> [Type] -> Constraint)
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#endif
89+
HasServer ty) => HasServer (ty :> sub) context
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instance {-# OVERLAPPABLE #-} TypeError (NoInstanceFor (HasServer api context)) => HasServer api context

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