Update hlint.yaml and fix some hints in servant and servant-server

HLint.hs

@@ -1,6 +0,0 @@
-import "hint" HLint.Default
-
-ignore "Redundant do"
-ignore "Parse error"
-ignore "Use list comprehension"
-ignore "Use liftM"

hlint.yaml

@@ -0,0 +1,65 @@
+# HLint configuration file
+# https://github.com/ndmitchell/hlint
+##########################
+
+# This file contains a template configuration file, which is typically
+# placed as .hlint.yaml in the root of your project
+
+
+# Specify additional command line arguments
+#
+# - arguments: [--color, --cpp-simple, -XQuasiQuotes]
+
+
+# Control which extensions/flags/modules/functions can be used
+#
+# - extensions:
+#   - default: false # all extension are banned by default
+#   - name: [PatternGuards, ViewPatterns] # only these listed extensions can be used
+#   - {name: CPP, within: CrossPlatform} # CPP can only be used in a given module
+#
+# - flags:
+#   - {name: -w, within: []} # -w is allowed nowhere
+#
+# - modules:
+#   - {name: [Data.Set, Data.HashSet], as: Set} # if you import Data.Set qualified, it must be as 'Set'
+#   - {name: Control.Arrow, within: []} # Certain modules are banned entirely
+#
+# - functions:
+#   - {name: unsafePerformIO, within: []} # unsafePerformIO can only appear in no modules
+
+
+# Add custom hints for this project
+#
+# Will suggest replacing "wibbleMany [myvar]" with "wibbleOne myvar"
+# - error: {lhs: "wibbleMany [x]", rhs: wibbleOne x}
+
+
+# Turn on hints that are off by default
+#
+# Ban "module X(module X) where", to require a real export list
+# - warn: {name: Use explicit module export list}
+#
+# Replace a $ b $ c with a . b $ c
+# - group: {name: dollar, enabled: true}
+#
+# Generalise map to fmap, ++ to <>
+# - group: {name: generalise, enabled: true}
+
+
+# Ignore some builtin hints
+- ignore: {name: Redundant do}
+- ignore: {name: Parse error}
+- ignore: {name: Use fmap}
+- ignore: {name: Use list comprehension}
+- ignore: {name: Use lambda-case}
+- ignore: {name: Eta reduce}
+# - ignore: {name: Use const, within: SpecialModule} # Only within certain modules
+
+
+# Define some custom infix operators
+# - fixity: infixr 3 ~^#^~
+
+
+# To generate a suitable file for HLint do:
+# $ hlint --default > .hlint.yaml

servant-server/src/Servant/Server.hs

@@ -1,7 +1,6 @@
 {-# LANGUAGE ConstraintKinds   #-}
 {-# LANGUAGE DataKinds         #-}
 {-# LANGUAGE FlexibleContexts  #-}
-{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RankNTypes        #-}
 {-# LANGUAGE TypeFamilies      #-}
 

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

@@ -326,7 +326,7 @@ streamRouter splitHeaders method framingproxy ctypeproxy action = leafRouter $ \
                       write . BB.lazyByteString $ header framingproxy ctypeproxy
                       case boundary framingproxy ctypeproxy of
                            BoundaryStrategyBracket f ->
-                                    let go x = let bs = mimeRender ctypeproxy $ x
+                                    let go x = let bs = mimeRender ctypeproxy x
                                                    (before, after) = f bs
                                                in write (   BB.lazyByteString before
                                                          <> BB.lazyByteString bs

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

@@ -1,5 +1,4 @@
 {-# LANGUAGE CPP                        #-}
-{-# LANGUAGE DeriveDataTypeable         #-}
 {-# LANGUAGE DeriveGeneric              #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE MultiParamTypeClasses      #-}

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

@@ -1,7 +1,6 @@
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE GADTs #-}
-{-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE OverloadedStrings #-}
 module Servant.Server.Internal.Router where
 

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

@@ -3,12 +3,8 @@
 {-# LANGUAGE FlexibleInstances          #-}
 {-# LANGUAGE GADTs                      #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE KindSignatures             #-}
 {-# LANGUAGE MultiParamTypeClasses      #-}
-{-# LANGUAGE OverloadedStrings          #-}
 {-# LANGUAGE RecordWildCards            #-}
-{-# LANGUAGE StandaloneDeriving         #-}
-{-# LANGUAGE TupleSections              #-}
 {-# LANGUAGE TypeFamilies               #-}
 {-# LANGUAGE TypeOperators              #-}
 {-# LANGUAGE UndecidableInstances       #-}
@@ -82,7 +78,7 @@ instance MonadBaseControl b m => MonadBaseControl b (RouteResultT m) where
 
 instance MonadTransControl RouteResultT where
     type StT RouteResultT a = RouteResult a
-    liftWith f = RouteResultT $ liftM return $ f $ runRouteResultT
+    liftWith f = RouteResultT $ liftM return $ f runRouteResultT
     restoreT = RouteResultT
 
 instance MonadThrow m => MonadThrow (RouteResultT m) where
@@ -367,7 +363,7 @@ runAction :: Delayed env (Handler a)
           -> (RouteResult Response -> IO r)
           -> (a -> RouteResult Response)
           -> IO r
-runAction action env req respond k = runResourceT $ do
+runAction action env req respond k = runResourceT $
     runDelayed action env req >>= go >>= liftIO . respond
   where
     go (Fail e)      = return $ Fail e

servant/src/Servant/API/ContentTypes.hs

@@ -282,7 +282,7 @@ instance OVERLAPPABLE_
          , AllMimeRender (ctyp' ': ctyps) a
          ) => AllMimeRender (ctyp ': ctyp' ': ctyps) a where
     allMimeRender _ a =
-        (map (, bs) $ NE.toList $ contentTypes pctyp)
+        map (, bs) (NE.toList $ contentTypes pctyp)
         ++ allMimeRender pctyps a
       where
         bs     = mimeRender pctyp a
@@ -317,10 +317,10 @@ instance ( MimeUnrender ctyp a
          , AllMimeUnrender ctyps a
          ) => AllMimeUnrender (ctyp ': ctyps) a where
     allMimeUnrender _ =
-        (map mk $ NE.toList $ contentTypes pctyp)
+        map mk (NE.toList $ contentTypes pctyp)
         ++ allMimeUnrender pctyps
       where
-        mk ct   = (ct, \bs -> mimeUnrenderWithType pctyp ct bs)
+        mk ct   = (ct, mimeUnrenderWithType pctyp ct)
         pctyp  = Proxy :: Proxy ctyp
         pctyps = Proxy :: Proxy ctyps
 

servant/src/Servant/API/Header.hs

@@ -1,6 +1,5 @@
 {-# LANGUAGE DataKinds          #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveFunctor      #-}
 {-# LANGUAGE PolyKinds          #-}
 {-# OPTIONS_HADDOCK not-home    #-}
 module Servant.API.Header (

servant/src/Servant/API/ResponseHeaders.hs

@@ -67,7 +67,7 @@ data HList a where
 
 type family HeaderValMap (f :: * -> *) (xs :: [*]) where
     HeaderValMap f '[]                = '[]
-    HeaderValMap f (Header h x ': xs) = Header h (f x) ': (HeaderValMap f xs)
+    HeaderValMap f (Header h x ': xs) = Header h (f x) ': HeaderValMap f xs
 
 
 class BuildHeadersTo hs where
@@ -80,7 +80,7 @@ instance OVERLAPPING_ BuildHeadersTo '[] where
     buildHeadersTo _ = HNil
 
 instance OVERLAPPABLE_ ( FromHttpApiData v, BuildHeadersTo xs, KnownSymbol h )
-         => BuildHeadersTo ((Header h v) ': xs) where
+         => BuildHeadersTo (Header h v ': xs) where
     buildHeadersTo headers =
       let wantedHeader = CI.mk . pack $ symbolVal (Proxy :: Proxy h)
           matching = snd <$> filter (\(h, _) -> h == wantedHeader) headers

servant/src/Servant/API/Stream.hs

@@ -40,7 +40,7 @@ instance ToStreamGenerator StreamGenerator a
    where toStreamGenerator x = x
 
 -- | Clients reading from streaming endpoints can be implemented as producing a @ResultStream@ that captures the setup, takedown, and incremental logic for a read, being an IO continuation that takes a producer of Just either values or errors that terminates with a Nothing.
-data ResultStream a = ResultStream ((forall b. (IO (Maybe (Either String a)) -> IO b) -> IO b))
+newtype ResultStream a = ResultStream (forall b. (IO (Maybe (Either String a)) -> IO b) -> IO b)
 
 -- | BuildFromStream is intended to be implemented for types such as Conduit, Pipe, etc. By implementing this class, all such streaming abstractions can be used directly on the client side for talking to streaming endpoints.
 class BuildFromStream a b where

servant/src/Servant/Utils/Enter.hs

@@ -1,5 +1,4 @@
 {-# LANGUAGE CPP                    #-}
-{-# LANGUAGE DeriveDataTypeable     #-}
 {-# LANGUAGE FlexibleInstances      #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE MultiParamTypeClasses  #-}