Add .hlint.yaml, fix some hlint warns, ignore others

Note: {-# ANN #-} start the GHCi interpreter (like TemplateHaskell!),
so I removed that.

.hlint.yaml

@@ -0,0 +1,5 @@
+# Ignore some builtin hints
+- ignore: {name: "Use import/export shortcut" }
+- ignore: {name: "Use tuple-section" }
+- ignore: {name: "Use newtype instead of data" } # ArgumentFields
+- ignore: {name: "Use fmap" } # we use liftM because Functor isn't superclass of Monad prior AMP

Options/Applicative.hs

@@ -232,5 +232,3 @@ import Options.Applicative.Builder
 import Options.Applicative.Builder.Completer
 import Options.Applicative.Extra
 import Options.Applicative.Types
-
-{-# ANN module "HLint: ignore Use import/export shortcut" #-}

Options/Applicative/Common.hs

@@ -100,7 +100,7 @@ optMatches disambiguate opt (OptWord arg1 val) = case opt of
     guard $ is_short arg1 || isNothing val
     Just $ do
       args <- get
-      let val' = (\s -> '-' : s) <$> val
+      let val' = ('-' :) <$> val
       put $ maybeToList val' ++ args
       return x
   _ -> Nothing
@@ -173,7 +173,7 @@ searchArg prefs arg = searchParser $ \opt -> do
           args <- get <* put []
           fmap pure . lift $ enterContext arg subp *> runParserInfo subp args <* exitContext
 
-        (Just subp, Backtrack) -> fmap pure . lift . StateT $ \args -> do
+        (Just subp, Backtrack) -> fmap pure . lift . StateT $ \args ->
           enterContext arg subp *> runParser (infoPolicy subp) CmdStart (infoParser subp) args <* exitContext
 
         (Just subp, SubparserInline) -> lift $ do

Options/Applicative/Help/Core.hs

@@ -55,7 +55,7 @@ optDesc pprefs style info opt =
         | not show_opt
         = mempty
         | otherwise
-        = desc <> suffix
+        = desc `mappend` suffix
       modified
         = maybe id fmap (optDescMod opt) rendered
   in  (modified, wrapping)
@@ -164,8 +164,8 @@ footerHelp chunk = mempty { helpFooter = chunk }
 
 -- | Generate the help text for a program.
 parserHelp :: ParserPrefs -> Parser a -> ParserHelp
-parserHelp pprefs p = bodyHelp . vsepChunks $
-  ( with_title "Available options:" (fullDesc pprefs p) )
+parserHelp pprefs p = bodyHelp . vsepChunks
+  $ with_title "Available options:" (fullDesc pprefs p)
   : (group_title <$> cs)
   where
     def = "Available commands:"

Options/Applicative/Help/Levenshtein.hs

@@ -43,10 +43,10 @@ editDistance a b = last $
         -- will have an edit distance of 1.
         doDiag (ach:ach':as) (bch:bch':bs) nw n w
           | ach' == bch && ach == bch'
-          = nw : (doDiag (ach' : as) (bch' : bs) nw (tail n) (tail w))
+          = nw : doDiag (ach' : as) (bch' : bs) nw (tail n) (tail w)
         -- Standard case
         doDiag (ach:as) (bch:bs) nw n w =
-          me : (doDiag as bs me (tail n) (tail w))
+          me : doDiag as bs me (tail n) (tail w)
           where
             me =
               if ach == bch