Follow HLint suggestion: use <$>

.hlint.yaml

@@ -11,7 +11,6 @@
 - ignore: {name: "Redundant return"} # 7 hints
 - ignore: {name: "Use ++"} # 4 hints
 - ignore: {name: "Use :"} # 30 hints
-- ignore: {name: "Use <$>"} # 83 hints
 - ignore: {name: "Use Down"} # 3 hints
 - ignore: {name: "Use camelCase"} # 92 hints
 - ignore: {name: "Use const"} # 36 hints

Cabal-syntax/src/Distribution/Backpack.hs

@@ -183,8 +183,7 @@ instance Parsec OpenModule where
       parsecOpenModule = do
         uid <- parsec
         _ <- P.char ':'
-        mod_name <- parsec
-        return (OpenModule uid mod_name)
+        OpenModule uid <$> parsec
 
       parsecModuleVar = do
         _ <- P.char '<'

Cabal-syntax/src/Distribution/InstalledPackageInfo.hs

@@ -134,11 +134,11 @@ showFullInstalledPackageInfo = P.showFields (const NoComment) . prettyFieldGramm
 -- Just "maintainer: Tester"
 showInstalledPackageInfoField :: String -> Maybe (InstalledPackageInfo -> String)
 showInstalledPackageInfoField fn =
-  fmap (\g -> Disp.render . ppField fn . g) $ fieldDescrPretty ipiFieldGrammar (toUTF8BS fn)
+  (\g -> Disp.render . ppField fn . g) <$> fieldDescrPretty ipiFieldGrammar (toUTF8BS fn)
 
 showSimpleInstalledPackageInfoField :: String -> Maybe (InstalledPackageInfo -> String)
 showSimpleInstalledPackageInfoField fn =
-  fmap (Disp.renderStyle myStyle .) $ fieldDescrPretty ipiFieldGrammar (toUTF8BS fn)
+  (Disp.renderStyle myStyle .) <$> fieldDescrPretty ipiFieldGrammar (toUTF8BS fn)
   where
     myStyle = Disp.style{Disp.mode = Disp.LeftMode}
 

Cabal-syntax/src/Distribution/SPDX/LicenseExpression.hs

@@ -114,8 +114,7 @@ instance Parsec LicenseExpression where
 
       simple = do
         s <- parsec
-        exc <- exception
-        return $ ELicense s exc
+        ELicense s <$> exception
 
       exception = P.optional $ P.try (spaces1 *> P.string "WITH" *> spaces1) *> parsec
 

Cabal-syntax/src/Distribution/System.hs

@@ -297,8 +297,7 @@ instance Parsec Platform where
   parsec = do
     arch <- parsecDashlessArch
     _ <- P.char '-'
-    os <- parsec
-    return (Platform arch os)
+    Platform arch <$> parsec
     where
       parsecDashlessArch = classifyArch Strict <$> dashlessIdent
 

Cabal-syntax/src/Distribution/Types/AbiDependency.hs

@@ -34,8 +34,7 @@ instance Parsec AbiDependency where
   parsec = do
     uid <- parsec
     _ <- P.char '='
-    abi <- parsec
-    return (AbiDependency uid abi)
+    AbiDependency uid <$> parsec
 
 instance Binary AbiDependency
 instance Structured AbiDependency

Cabal-syntax/src/Distribution/Types/CondTree.hs

@@ -119,9 +119,7 @@ traverseCondTreeV f (CondNode a ifs) =
 -- | @@Traversal@@ for the data
 traverseCondBranchA :: L.Traversal (CondBranch v a) (CondBranch v b) a b
 traverseCondBranchA f (CondBranch cnd t me) =
-  pure (CondBranch cnd)
-    <*> traverseCondTreeA f t
-    <*> traverse (traverseCondTreeA f) me
+  CondBranch cnd <$> traverseCondTreeA f t <*> traverse (traverseCondTreeA f) me
 
 -- | @@Traversal@@ for the variables
 traverseCondBranchV :: L.Traversal (CondBranch v a) (CondBranch w a) v w

Cabal-syntax/src/Distribution/Types/GenericPackageDescription/Lens.hs

@@ -79,10 +79,8 @@ allCondTrees
   -> GenericPackageDescription
   -> f GenericPackageDescription
 allCondTrees f (GenericPackageDescription p v a1 x1 x2 x3 x4 x5 x6) =
-  pure (GenericPackageDescription p)
-    <*> pure v
-    <*> pure a1
-    <*> traverse f x1
+  GenericPackageDescription p v a1
+    <$> traverse f x1
     <*> (traverse . _2) f x2
     <*> (traverse . _2) f x3
     <*> (traverse . _2) f x4

Cabal-syntax/src/Distribution/Types/Mixin.hs

@@ -62,8 +62,7 @@ instance Parsec Mixin where
       versionGuardMultilibs
       LSubLibName <$> parsec
     P.spaces
-    incl <- parsec
-    return (mkMixin pn ln incl)
+    mkMixin pn ln <$> parsec
 
 versionGuardMultilibs :: CabalParsing m => m ()
 versionGuardMultilibs = do

Cabal-syntax/src/Distribution/Types/Module.hs

@@ -35,8 +35,7 @@ instance Parsec Module where
   parsec = do
     uid <- parsec
     _ <- P.char ':'
-    mod_name <- parsec
-    return (Module uid mod_name)
+    Module uid <$> parsec
 
 instance NFData Module where
   rnf (Module uid mod_name) = rnf uid `seq` rnf mod_name

Cabal-syntax/src/Distribution/Types/PackageDescription.hs

@@ -428,15 +428,15 @@ enabledComponents pkg enabled = filter (componentEnabled enabled) $ pkgBuildable
 
 lookupComponent :: PackageDescription -> ComponentName -> Maybe Component
 lookupComponent pkg (CLibName name) =
-  fmap CLib $ find ((name ==) . libName) (allLibraries pkg)
+  CLib <$> find ((name ==) . libName) (allLibraries pkg)
 lookupComponent pkg (CFLibName name) =
-  fmap CFLib $ find ((name ==) . foreignLibName) (foreignLibs pkg)
+  CFLib <$> find ((name ==) . foreignLibName) (foreignLibs pkg)
 lookupComponent pkg (CExeName name) =
-  fmap CExe $ find ((name ==) . exeName) (executables pkg)
+  CExe <$> find ((name ==) . exeName) (executables pkg)
 lookupComponent pkg (CTestName name) =
-  fmap CTest $ find ((name ==) . testName) (testSuites pkg)
+  CTest <$> find ((name ==) . testName) (testSuites pkg)
 lookupComponent pkg (CBenchName name) =
-  fmap CBench $ find ((name ==) . benchmarkName) (benchmarks pkg)
+  CBench <$> find ((name ==) . benchmarkName) (benchmarks pkg)
 
 getComponent :: PackageDescription -> ComponentName -> Component
 getComponent pkg cname = fromMaybe missingComponent (lookupComponent pkg cname)

Cabal-syntax/src/Distribution/Types/VersionRange/Internal.hs

@@ -364,8 +364,7 @@ versionRangeParser digitParser csv = expr
         _ <- P.string "||"
         checkOp
         P.spaces
-        e <- expr
-        return (unionVersionRanges t e)
+        unionVersionRanges t <$> expr
         <|> return t
     term = do
       f <- factor
@@ -374,8 +373,7 @@ versionRangeParser digitParser csv = expr
         _ <- P.string "&&"
         checkOp
         P.spaces
-        t <- term
-        return (intersectVersionRanges f t)
+        intersectVersionRanges f <$> term
         <|> return f
     factor = parens expr <|> prim
 

Cabal-syntax/src/Distribution/Utils/MD5.hs

@@ -56,8 +56,7 @@ binaryPutMD5 (Fingerprint a b) = do
 binaryGetMD5 :: Get MD5
 binaryGetMD5 = do
   a <- getWord64le
-  b <- getWord64le
-  return (Fingerprint a b)
+  Fingerprint a <$> getWord64le
 
 -- |
 --

Cabal/src/Distribution/Simple/GHC/Build/Link.hs

@@ -521,7 +521,7 @@ linkFLib flib bi lbi linkerOpts (way, buildOpts) targetDir runGhcProg = do
             { ghcOptLinkNoHsMain = toFlag True
             , ghcOptShared = toFlag True
             , ghcOptFPic = toFlag True
-            , ghcOptLinkModDefFiles = toNubListR $ fmap getSymbolicPath $ foreignLibModDefFile flib
+            , ghcOptLinkModDefFiles = toNubListR (getSymbolicPath <$> foreignLibModDefFile flib)
             }
       ForeignLibNativeStatic ->
         -- this should be caught by buildFLib

Cabal/src/Distribution/Simple/GHCJS.hs

@@ -1554,7 +1554,7 @@ gbuild verbosity numJobs pkg_descr lbi bm clbi = do
                   , ghcOptLinkLibs = rtsOptLinkLibs
                   , ghcOptLinkLibPath = toNubListR $ map makeSymbolicPath $ rtsLibPaths rtsInfo
                   , ghcOptFPic = toFlag True
-                  , ghcOptLinkModDefFiles = toNubListR $ fmap getSymbolicPath $ gbuildModDefFiles bm
+                  , ghcOptLinkModDefFiles = toNubListR (getSymbolicPath <$> gbuildModDefFiles bm)
                   }
             ForeignLibNativeStatic ->
               -- this should be caught by buildFLib

Cabal/src/Distribution/Simple/InstallDirs.hs

@@ -73,7 +73,6 @@ import qualified Prelude
 import Foreign
 import Foreign.C
 #endif
-
 -- ---------------------------------------------------------------------------
 -- Installation directories
 
@@ -208,46 +207,47 @@ defaultInstallDirs' False comp userInstall _hasLibs = do
     case buildOS of
       Windows -> return "$prefix"
       _ -> return ("$prefix" </> "lib")
-  return $
-    fmap toPathTemplate $
-      InstallDirs
-        { prefix = installPrefix
-        , bindir = "$prefix" </> "bin"
-        , libdir = installLibDir
-        , libsubdir = case comp of
-            UHC -> "$pkgid"
-            _other -> "$abi" </> "$libname"
-        , dynlibdir =
-            "$libdir" </> case comp of
+  return
+    ( toPathTemplate
+        <$> InstallDirs
+          { prefix = installPrefix
+          , bindir = "$prefix" </> "bin"
+          , libdir = installLibDir
+          , libsubdir = case comp of
               UHC -> "$pkgid"
-              _other -> "$abi"
-        , bytecodelibdir = "$libdir" </> "$libsubdir"
-        , libexecsubdir = "$abi" </> "$pkgid"
-        , flibdir = "$libdir"
-        , libexecdir = case buildOS of
-            Windows -> "$prefix" </> "$libname"
-            Haiku -> "$libdir"
-            _other -> "$prefix" </> "libexec"
-        , includedir = case buildOS of
-            Haiku -> "$prefix" </> "develop" </> "headers"
-            _other -> "$libdir" </> "$libsubdir" </> "include"
-        , datadir = case buildOS of
-            Windows -> "$prefix"
-            Haiku -> "$prefix" </> "data"
-            _other -> "$prefix" </> "share"
-        , datasubdir = "$abi" </> "$pkgid"
-        , docdir = case buildOS of
-            Haiku -> "$prefix" </> "documentation"
-            _other -> "$datadir" </> "doc" </> "$abi" </> "$pkgid"
-        , mandir = case buildOS of
-            Haiku -> "$docdir" </> "man"
-            _other -> "$datadir" </> "man"
-        , htmldir = "$docdir" </> "html"
-        , haddockdir = "$htmldir"
-        , sysconfdir = case buildOS of
-            Haiku -> "boot" </> "system" </> "settings"
-            _other -> "$prefix" </> "etc"
-        }
+              _other -> "$abi" </> "$libname"
+          , dynlibdir =
+              "$libdir" </> case comp of
+                UHC -> "$pkgid"
+                _other -> "$abi"
+          , bytecodelibdir = "$libdir" </> "$libsubdir"
+          , libexecsubdir = "$abi" </> "$pkgid"
+          , flibdir = "$libdir"
+          , libexecdir = case buildOS of
+              Windows -> "$prefix" </> "$libname"
+              Haiku -> "$libdir"
+              _other -> "$prefix" </> "libexec"
+          , includedir = case buildOS of
+              Haiku -> "$prefix" </> "develop" </> "headers"
+              _other -> "$libdir" </> "$libsubdir" </> "include"
+          , datadir = case buildOS of
+              Windows -> "$prefix"
+              Haiku -> "$prefix" </> "data"
+              _other -> "$prefix" </> "share"
+          , datasubdir = "$abi" </> "$pkgid"
+          , docdir = case buildOS of
+              Haiku -> "$prefix" </> "documentation"
+              _other -> "$datadir" </> "doc" </> "$abi" </> "$pkgid"
+          , mandir = case buildOS of
+              Haiku -> "$docdir" </> "man"
+              _other -> "$datadir" </> "man"
+          , htmldir = "$docdir" </> "html"
+          , haddockdir = "$htmldir"
+          , sysconfdir = case buildOS of
+              Haiku -> "boot" </> "system" </> "settings"
+              _other -> "$prefix" </> "etc"
+          }
+    )
 
 -- ---------------------------------------------------------------------------
 -- Converting directories, absolute or prefix-relative

Cabal/src/Distribution/Simple/Program/Find.hs

@@ -180,9 +180,7 @@ programSearchPathAsPATHVar searchpath = do
   return (intercalate [searchPathSeparator] (concat ess))
   where
     getEntries (ProgramSearchPathDir dir) = return [dir]
-    getEntries ProgramSearchPathDefault = do
-      env <- getEnvironment
-      return (maybe [] splitSearchPath (lookup "PATH" env))
+    getEntries ProgramSearchPathDefault = maybe [] splitSearchPath . lookup "PATH" <$> getEnvironment
 
 -- | Get the system search path. On Unix systems this is just the @$PATH@ env
 -- var, but on windows it's a bit more complicated.

Cabal/src/Distribution/Simple/Register.hs

@@ -327,9 +327,9 @@ abiHash
 abiHash verbosity pkg distPref lbi lib clbi =
   case compilerFlavor comp of
     GHC -> do
-      fmap mkAbiHash $ GHC.libAbiHash verbosity pkg lbi' lib clbi
+      mkAbiHash <$> GHC.libAbiHash verbosity pkg lbi' lib clbi
     GHCJS -> do
-      fmap mkAbiHash $ GHCJS.libAbiHash verbosity pkg lbi' lib clbi
+      mkAbiHash <$> GHCJS.libAbiHash verbosity pkg lbi' lib clbi
     _ -> return (mkAbiHash "")
   where
     comp = compiler lbi
@@ -713,8 +713,7 @@ relocatableInstalledPackageInfo pkg abi_hash lib lbi clbi pkgroot =
     bi = libBuildInfo lib
 
     installDirs =
-      fmap (("${pkgroot}" </>) . shortRelativePath (getSymbolicPath pkgroot)) $
-        absoluteComponentInstallDirs pkg lbi (componentUnitId clbi) NoCopyDest
+      ("${pkgroot}" </>) . shortRelativePath (getSymbolicPath pkgroot) <$> absoluteComponentInstallDirs pkg lbi (componentUnitId clbi) NoCopyDest
 
 -- -----------------------------------------------------------------------------
 -- Unregistration

Cabal/src/Distribution/Simple/Setup/Config.hs

@@ -923,8 +923,7 @@ parsecPromisedComponent = do
         then LMainLibName
         else LSubLibName ucn
   _ <- P.char '='
-  cid <- parsec
-  return $ PromisedComponent pn ln cid
+  PromisedComponent pn ln <$> parsec
 
 prettyPromisedComponent :: PromisedComponent -> String
 prettyPromisedComponent (PromisedComponent pn cn cid) =
@@ -946,8 +945,7 @@ parsecGivenComponent = do
         then LMainLibName
         else LSubLibName ucn
   _ <- P.char '='
-  cid <- parsec
-  return $ GivenComponent pn ln cid
+  GivenComponent pn ln <$> parsec
 
 prettyGivenComponent :: GivenComponent -> String
 prettyGivenComponent (GivenComponent pn cn cid) =

Cabal/src/Distribution/Simple/SetupHooks/Errors.hs

@@ -122,9 +122,7 @@ rulesExceptionMessage = \case
       showCycle :: (RuleBinary, [Graph.Tree RuleBinary]) -> String
       showCycle (r, rs) =
         unlines . map ("  " ++) . lines $
-          Tree.drawTree $
-            fmap show $
-              Tree.Node r rs
+          Tree.drawTree (show <$> Tree.Node r rs)
   CantFindSourceForRuleDependencies _r deps ->
     unlines $
       ("Pre-build rules: can't find source for rule " ++ what ++ ":")

Cabal/src/Distribution/Simple/SrcDist.hs

@@ -272,13 +272,13 @@ listPackageSources' verbosity rip mbWorkDir pkg_descr pps =
         . withAllLib
         $ \l -> do
           let lbi = libBuildInfo l
-              incls = fmap getSymbolicPath $ filter (`notElem` autogenIncludes lbi) (installIncludes lbi)
+              incls = getSymbolicPath <$> filter (`notElem` autogenIncludes lbi) (installIncludes lbi)
               relincdirs = fmap getSymbolicPath $ sameDirectory : mapMaybe symbolicPathRelative_maybe (includeDirs lbi)
           traverse (fmap (makeSymbolicPath . snd) . findIncludeFile verbosity cwd relincdirs) incls
     , -- Setup script, if it exists.
-      fmap (maybe [] (\f -> [makeSymbolicPath f])) $ findSetupFile cwd
+      maybe [] (\f -> [makeSymbolicPath f]) <$> findSetupFile cwd
     , -- SetupHooks script, if it exists.
-      fmap (maybe [] (\f -> [makeSymbolicPath f])) $ findSetupHooksFile cwd
+      maybe [] (\f -> [makeSymbolicPath f]) <$> findSetupHooksFile cwd
     , -- The .cabal file itself.
       fmap (\d -> [d]) (coerceSymbolicPath . relativeSymbolicPath <$> tryFindPackageDesc verbosity mbWorkDir)
     ]

Cabal/src/Distribution/Simple/Test/LibV09.hs

@@ -156,13 +156,12 @@ runTest verbHandles pkg_descr lbi clbi hpcMarkupInfo flags suite = do
     -- Generate TestSuiteLog from executable exit code and a machine-
     -- readable test log
     suiteLog <-
-      fmap
-        ( \s ->
-            (\l -> l{logFile = finalLogName l})
-              . fromMaybe (error $ "panic! read @TestSuiteLog " ++ show s)
-              $ readMaybe s -- TODO: eradicateNoParse
+      ( \s ->
+          (\l -> l{logFile = finalLogName l})
+            . fromMaybe (error $ "panic! read @TestSuiteLog " ++ show s)
+            $ readMaybe s -- TODO: eradicateNoParse
         )
-        $ readFile tempLog
+        <$> readFile tempLog
 
     -- Write summary notice to log file indicating start of test suite
     appendFile (logFile suiteLog) $ summarizeSuiteStart testName'