Normalize parentheses in constraints

CHANGELOG.md

@@ -6,6 +6,9 @@
 * Now `.ormolu` fixity override files can use both LF and CRLF line endings.
   [PR 969](https://github.com/tweag/ormolu/pull/969).
 
+* Normalize parentheses around constraints. [Issue
+  264](https://github.com/tweag/ormolu/issues/264).
+
 ## Ormolu 0.5.2.0
 
 * Eliminated the `fixity-th` Cabal flag because it caused issues on GHC 9.4 as

data/examples/declaration/class/default-signatures-simple-out.hs

@@ -4,5 +4,5 @@ module Main where
 class Foo a where
   -- | Foo
   foo :: a -> String
-  default foo :: Show a => a -> String
+  default foo :: (Show a) => a -> String
   foo = show

data/examples/declaration/class/super-classes-out.hs

@@ -1,6 +1,6 @@
 class Foo a
 
-class Foo a => Bar a
+class (Foo a) => Bar a
 
 class
   (Foo a, Bar a) =>

data/examples/declaration/data/existential-multiline-out.hs

@@ -2,7 +2,7 @@
 
 data Foo
   = forall a. MkFoo a (a -> Bool)
-  | forall a. Eq a => MkBar a
+  | forall a. (Eq a) => MkBar a
 
 data Bar
   = forall x y.

data/examples/declaration/data/existential-out.hs

@@ -2,4 +2,4 @@
 
 data Foo = forall a. MkFoo a (a -> Bool)
 
-data Bar = forall a b. a + b => Bar a b
+data Bar = forall a b. (a + b) => Bar a b

data/examples/declaration/instance/contexts-out.hs

@@ -1,4 +1,4 @@
-instance Eq a => Eq [a] where (==) _ _ = False
+instance (Eq a) => Eq [a] where (==) _ _ = False
 
 instance
   ( Ord a,

data/examples/declaration/instance/newlines-between-methods-out.hs

@@ -1,4 +1,4 @@
-instance Num a => Num (Diff a) where
+instance (Num a) => Num (Diff a) where
   D u dudx + D v dvdx = D (u + v) (dudx + dvdx)
   D u dudx - D v dvdx = D (u - v) (dudx - dvdx)
   D u dudx * D v dvdx = D (u * v) (u * dvdx + v * dudx)

data/examples/declaration/signature/specialize/specialize-instance-out.hs

@@ -8,7 +8,7 @@ instance (Eq a) => Eq (Foo a) where
 
 instance (Num r, V.Vector v r, Factored m r) => Num (VT v m r) where
   {-# SPECIALIZE instance
-    ( Factored m Int => Num (VT U.Vector m Int)
+    ( (Factored m Int) => Num (VT U.Vector m Int)
     )
     #-}
   VT x + VT y = VT $ V.zipWith (+) x y

data/examples/declaration/signature/specialize/specialize-out.hs

@@ -1,13 +1,13 @@
-foo :: Num a => a -> a
+foo :: (Num a) => a -> a
 foo = id
 {-# SPECIALIZE foo :: Int -> Int #-}
 {-# SPECIALIZE INLINE foo :: Float -> Float #-}
 
 {-# SPECIALIZE NOINLINE [2] bar :: Int -> Int #-}
-bar :: Num a => a -> a
+bar :: (Num a) => a -> a
 bar = id
 
-baz :: Num a => a -> a
+baz :: (Num a) => a -> a
 baz = id
 {-# SPECIALIZE [~2] baz ::
   Int ->
@@ -20,5 +20,5 @@ baz = id
   Bool,
   Integer -> Bool
   #-}
-fits13Bits :: Integral a => a -> Bool
+fits13Bits :: (Integral a) => a -> Bool
 fits13Bits x = x >= -4096 && x < 4096

data/examples/declaration/signature/type/unicode-out.hs

@@ -1,4 +1,4 @@
 {-# LANGUAGE UnicodeSyntax #-}
 
-foo :: forall a. Show a => a -> String
+foo :: forall a. (Show a) => a -> String
 foo = const ()

data/examples/declaration/value/function/fancy-forall-0-out.hs

@@ -2,9 +2,9 @@ wrapError ::
   forall outertag innertag t outer inner m a.
   ( forall x. Coercible (t m x) (m x),
     forall m'.
-    HasCatch outertag outer m' =>
+    (HasCatch outertag outer m') =>
     HasCatch innertag inner (t m'),
     HasCatch outertag outer m
   ) =>
-  (forall m'. HasCatch innertag inner m' => m' a) ->
+  (forall m'. (HasCatch innertag inner m') => m' a) ->
   m a

data/examples/declaration/value/function/fancy-forall-1-out.hs

@@ -2,9 +2,9 @@ magnify ::
   forall outertag innertag t outer inner m a.
   ( forall x. Coercible (t m x) (m x),
     forall m'.
-    HasReader outertag outer m' =>
+    (HasReader outertag outer m') =>
     HasReader innertag inner (t m'),
     HasReader outertag outer m
   ) =>
-  (forall m'. HasReader innertag inner m' => m' a) ->
+  (forall m'. (HasReader innertag inner m') => m' a) ->
   m a

data/examples/declaration/value/function/let-multi-line-out.hs

@@ -17,7 +17,7 @@ inlineComment =
                    () -> undefined
    in go
 
-implicitParams :: HasCallStack => Int
+implicitParams :: (HasCallStack) => Int
 implicitParams =
   let ?cs = ?callstack
    in foo cs

data/examples/other/argument-comment-out.hs

@@ -5,12 +5,12 @@ foo ::
 foo _ = True
 
 foo ::
-  Foo a =>
+  (Foo a) =>
   -- | Foo
   Int ->
   Int
 foo ::
-  Foo a =>
+  (Foo a) =>
   -- | Foo
   Int ->
   Int

data/examples/other/cpp/separation-0a-out.hs

@@ -1,6 +1,6 @@
 {-# LANGUAGE CPP #-}
 
-instance Stream s => Monad (ParsecT e s m) where
+instance (Stream s) => Monad (ParsecT e s m) where
   return = pure
   (>>=) = pBind
 #if !(MIN_VERSION_base(4,13,0))

data/examples/other/cpp/separation-0b-out.hs

@@ -1,6 +1,6 @@
 {-# LANGUAGE CPP #-}
 
-instance Stream s => Monad (ParsecT e s m) where
+instance (Stream s) => Monad (ParsecT e s m) where
   return = pure
   (>>=) = pBind
 #if !(MIN_VERSION_base(4,13,0))

expected-failures/pipes.txt

@@ -201,7 +201,8 @@ src/Pipes/Core.hs
 + --    * ('Control.Monad.>=>'): sequence proxies
 
   -- | Run a self-contained 'Effect', converting it back to the base monad
-  runEffect :: Monad m => Effect m r -> m r
+- runEffect :: Monad m => Effect m r -> m r
++ runEffect :: (Monad m) => Effect m r -> m r
   runEffect = go
     where
       go p = case p of
@@ -509,11 +510,12 @@ src/Pipes/Core.hs
 
 -     'respond' is the identity of the respond category.
 - -}
+- respond :: Functor m => a -> Proxy x' x a' a m a'
 + -- | Send a value of type @a@ downstream and block waiting for a reply of type
 + --    @a'@
 + --
 + --    'respond' is the identity of the respond category.
-  respond :: Functor m => a -> Proxy x' x a' a m a'
++ respond :: (Functor m) => a -> Proxy x' x a' a m a'
   respond a = Respond a Pure
 - {-# INLINABLE [1] respond #-}
 -
@@ -542,7 +544,7 @@ src/Pipes/Core.hs
 + --
 + --    ('/>/') is the composition operator of the respond category.
 + (/>/) ::
-+   Functor m =>
++   (Functor m) =>
 +   (a -> Proxy x' x b' b m a') ->
 +   (b -> Proxy x' x c' c m b') ->
 +   (a -> Proxy x' x c' c m a')
@@ -566,7 +568,7 @@ src/Pipes/Core.hs
 + --
 + --    Point-ful version of ('/>/')
 + (//>) ::
-+   Functor m =>
++   (Functor m) =>
 +   Proxy x' x b' b m a' ->
 +   (b -> Proxy x' x c' c m b') ->
 +   Proxy x' x c' c m a'
@@ -754,10 +756,11 @@ src/Pipes/Core.hs
 
 -     'request' is the identity of the request category.
 - -}
+- request :: Functor m => a' -> Proxy a' a y' y m a
 + -- | Send a value of type @a'@ upstream and block waiting for a reply of type @a@
 + --
 + --    'request' is the identity of the request category.
-  request :: Functor m => a' -> Proxy a' a y' y m a
++ request :: (Functor m) => a' -> Proxy a' a y' y m a
   request a' = Request a' Pure
 - {-# INLINABLE [1] request #-}
 -
@@ -786,7 +789,7 @@ src/Pipes/Core.hs
 + --
 + --    ('\>\') is the composition operator of the request category.
 + (\>\) ::
-+   Functor m =>
++   (Functor m) =>
 +   (b' -> Proxy a' a y' y m b) ->
 +   (c' -> Proxy b' b y' y m c) ->
 +   (c' -> Proxy a' a y' y m c)
@@ -810,7 +813,7 @@ src/Pipes/Core.hs
 + --
 + --    Point-ful version of ('\>\')
 + (>\\) ::
-+   Functor m =>
++   (Functor m) =>
 +   (b' -> Proxy a' a y' y m b) ->
 +   Proxy b' b y' y m c ->
 +   Proxy a' a y' y m c
@@ -965,14 +968,15 @@ src/Pipes/Core.hs
 
 -     'push' is the identity of the push category.
 - -}
+- push :: Functor m => a -> Proxy a' a a' a m r
 + -- | Forward responses followed by requests
 + --
 + -- @
 + -- 'push' = 'respond' 'Control.Monad.>=>' 'request' 'Control.Monad.>=>' 'push'
 + -- @
 + --
 + --    'push' is the identity of the push category.
-  push :: Functor m => a -> Proxy a' a a' a m r
++ push :: (Functor m) => a -> Proxy a' a a' a m r
   push = go
     where
       go a = Respond a (\a' -> Request a' go)
@@ -1005,7 +1009,7 @@ src/Pipes/Core.hs
 + --
 + --    ('>~>') is the composition operator of the push category.
 + (>~>) ::
-+   Functor m =>
++   (Functor m) =>
 +   (_a -> Proxy a' a b' b m r) ->
 +   (b -> Proxy b' b c' c m r) ->
 +   (_a -> Proxy a' a c' c m r)
@@ -1029,7 +1033,7 @@ src/Pipes/Core.hs
 + --
 + --    Point-ful version of ('>~>')
 + (>>~) ::
-+   Functor m =>
++   (Functor m) =>
 +   Proxy a' a b' b m r ->
 +   (b -> Proxy b' b c' c m r) ->
 +   Proxy a' a c' c m r
@@ -1163,14 +1167,15 @@ src/Pipes/Core.hs
 
 -     'pull' is the identity of the pull category.
 - -}
+- pull :: Functor m => a' -> Proxy a' a a' a m r
 + -- | Forward requests followed by responses:
 + --
 + -- @
 + -- 'pull' = 'request' 'Control.Monad.>=>' 'respond' 'Control.Monad.>=>' 'pull'
 + -- @
 + --
 + --    'pull' is the identity of the pull category.
-  pull :: Functor m => a' -> Proxy a' a a' a m r
++ pull :: (Functor m) => a' -> Proxy a' a a' a m r
   pull = go
     where
       go a' = Request a' (\a -> Respond a go)
@@ -1203,7 +1208,7 @@ src/Pipes/Core.hs
 + --
 + --    ('>+>') is the composition operator of the pull category.
 + (>+>) ::
-+   Functor m =>
++   (Functor m) =>
 +   (b' -> Proxy a' a b' b m r) ->
 +   (_c' -> Proxy b' b c' c m r) ->
 +   (_c' -> Proxy a' a c' c m r)
@@ -1227,7 +1232,7 @@ src/Pipes/Core.hs
 + --
 + --    Point-ful version of ('>+>')
 + (+>>) ::
-+   Functor m =>
++   (Functor m) =>
 +   (b' -> Proxy a' a b' b m r) ->
 +   Proxy b' b c' c m r ->
 +   Proxy a' a c' c m r
@@ -1306,7 +1311,8 @@ src/Pipes/Core.hs
 + -- @
 
   -- | Switch the upstream and downstream ends
-  reflect :: Functor m => Proxy a' a b' b m r -> Proxy b b' a a' m r
+- reflect :: Functor m => Proxy a' a b' b m r -> Proxy b b' a a' m r
++ reflect :: (Functor m) => Proxy a' a b' b m r -> Proxy b b' a a' m r
   reflect = go
     where
       go p = case p of

extract-hackage-info/src/Main.hs

@@ -73,10 +73,10 @@ exitWithMsg t = do
   TIO.hPutStrLn stderr t
   exitWith (ExitFailure 1)
 
-showT :: Show a => a -> Text
+showT :: (Show a) => a -> Text
 showT = T.pack . show
 
-readT :: Read a => Text -> a
+readT :: (Read a) => Text -> a
 readT = read . T.unpack
 
 indentLines :: [Text] -> [Text]
@@ -390,7 +390,7 @@ extractHackageInfo filePath = do
   return result
 
 -- | Limit the number of items in a map.
-limitMap :: Ord k => Int -> Map k v -> Map k v
+limitMap :: (Ord k) => Int -> Map k v -> Map k v
 limitMap n = Map.fromList . take n . Map.toList
 
 data Config = Config

src/Ormolu.hs

@@ -54,7 +54,7 @@ import System.FilePath
 -- the 'cfgSourceType' field. Autodetection of source type won't happen
 -- here, see 'detectSourceType'.
 ormolu ::
-  MonadIO m =>
+  (MonadIO m) =>
   -- | Ormolu configuration
   Config RegionIndices ->
   -- | Location of source file
@@ -124,7 +124,7 @@ ormolu cfgWithIndices path originalInput = do
 -- the 'cfgSourceType' field. Autodetection of source type won't happen
 -- here, see 'detectSourceType'.
 ormoluFile ::
-  MonadIO m =>
+  (MonadIO m) =>
   -- | Ormolu configuration
   Config RegionIndices ->
   -- | Location of source file
@@ -140,7 +140,7 @@ ormoluFile cfg path =
 -- the 'cfgSourceType' field. Autodetection of source type won't happen
 -- here, see 'detectSourceType'.
 ormoluStdin ::
-  MonadIO m =>
+  (MonadIO m) =>
   -- | Ormolu configuration
   Config RegionIndices ->
   -- | Resulting rendition
@@ -153,7 +153,7 @@ ormoluStdin cfg =
 
 -- | A wrapper around 'parseModule'.
 parseModule' ::
-  MonadIO m =>
+  (MonadIO m) =>
   -- | Ormolu configuration
   Config RegionDeltas ->
   -- | Fixity Map for operators

src/Ormolu/Diff/ParseResult.hs

@@ -74,7 +74,7 @@ diffCommentStream (CommentStream cs) (CommentStream cs')
 --     * LayoutInfo (brace style) in extension fields
 --     * Empty contexts in type classes
 --     * Parens around derived type classes
-matchIgnoringSrcSpans :: Data a => a -> a -> ParseResultDiff
+matchIgnoringSrcSpans :: (Data a) => a -> a -> ParseResultDiff
 matchIgnoringSrcSpans a = genericQuery a
   where
     genericQuery :: GenericQ (GenericQ ParseResultDiff)
@@ -150,7 +150,7 @@ matchIgnoringSrcSpans a = genericQuery a
     unicodeArrowStyleEq (HsLinearArrow _) (castArrow -> Just (HsLinearArrow _)) = Same
     unicodeArrowStyleEq (HsExplicitMult _ _ t) (castArrow -> Just (HsExplicitMult _ _ t')) = genericQuery t t'
     unicodeArrowStyleEq _ _ = Different []
-    castArrow :: Typeable a => a -> Maybe (HsArrow GhcPs)
+    castArrow :: (Typeable a) => a -> Maybe (HsArrow GhcPs)
     castArrow = cast
     -- LayoutInfo ~ XClassDecl GhcPs tracks brace information
     layoutInfoEq :: LayoutInfo -> GenericQ ParseResultDiff

src/Ormolu/Fixity.hs

@@ -223,7 +223,7 @@ mergeFixityMaps popularityMap threshold packageMaps =
       Map.map
         (flip Map.singleton (packageName :| []))
         opsMap
-    maxWith :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
+    maxWith :: (Ord b) => (a -> b) -> NonEmpty a -> NonEmpty a
     maxWith f xs = snd $ foldl' comp (f h, h :| []) t
       where
         h :| t = xs