diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,23 @@
+## Fourmolu 0.14.1.0
+
+* Fix `single-constraint-parens: never` for nested quantified constraints ([#374](https://github.com/fourmolu/fourmolu/issues/374))
+
+* Fix `column-limit` with `BlockArguments` ([#377](https://github.com/fourmolu/fourmolu/issues/377))
+
+* Fixed an issue where re-exporting a module with Haddock comments + `import-exports=leading` was indented too far ([#381](https://github.com/fourmolu/fourmolu/issues/381))
+
+### Upstream changes:
+
+#### Ormolu 0.7.3.0
+
+* Switched to `ghc-lib-parser-9.8`, with the following new syntactic features:
+  * `ExtendedLiterals`: `123#Int8` is a literal of type `Int8#`. (disabled by
+    default)
+  * `TypeAbstractions`: `@k`-binders in data type declarations (enabled by
+    default)
+  * GHC proposal [#134](https://github.com/ghc-proposals/ghc-proposals/blob/0b652bd70258e354dfe4a05940182007596f8bf7/proposals/0134-deprecating-exports-proposal.rst): deprecating/warning about exports
+  * GHC proposal [#541](https://github.com/ghc-proposals/ghc-proposals/blob/0b652bd70258e354dfe4a05940182007596f8bf7/proposals/0541-warning-pragmas-with-categories.rst): warning categories
+
 ## Fourmolu 0.14.0.0
 
 * Provide `resolvePrinterOpts` instead of `fillMissingPrinterOpts`
diff --git a/Setup.hs b/Setup.hs
deleted file mode 100644
--- a/Setup.hs
+++ /dev/null
@@ -1,6 +0,0 @@
-module Main (main) where
-
-import Distribution.Simple
-
-main :: IO ()
-main = defaultMain
diff --git a/data/examples/declaration/data/invisible-binders-four-out.hs b/data/examples/declaration/data/invisible-binders-four-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/data/invisible-binders-four-out.hs
@@ -0,0 +1,2 @@
+type T :: forall k. k -> forall j. j -> Type
+data T @k (a :: k) @(j :: Type) (b :: j)
diff --git a/data/examples/declaration/data/invisible-binders-out.hs b/data/examples/declaration/data/invisible-binders-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/data/invisible-binders-out.hs
@@ -0,0 +1,2 @@
+type T :: forall k. k -> forall j. j -> Type
+data T @k (a :: k) @(j :: Type) (b :: j)
diff --git a/data/examples/declaration/data/invisible-binders.hs b/data/examples/declaration/data/invisible-binders.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/data/invisible-binders.hs
@@ -0,0 +1,2 @@
+type T :: forall k. k -> forall j. j -> Type
+data T @k (a :: k) @(j :: Type) (b :: j)
diff --git a/data/examples/declaration/signature/fixity/infix-four-out.hs b/data/examples/declaration/signature/fixity/infix-four-out.hs
--- a/data/examples/declaration/signature/fixity/infix-four-out.hs
+++ b/data/examples/declaration/signature/fixity/infix-four-out.hs
@@ -1,2 +1,4 @@
 infix 0 <?>
 infix 9 <^-^>
+
+infix 2 ->
diff --git a/data/examples/declaration/signature/fixity/infix-out.hs b/data/examples/declaration/signature/fixity/infix-out.hs
--- a/data/examples/declaration/signature/fixity/infix-out.hs
+++ b/data/examples/declaration/signature/fixity/infix-out.hs
@@ -1,3 +1,5 @@
 infix 0 <?>
 
 infix 9 <^-^>
+
+infix 2 ->
diff --git a/data/examples/declaration/signature/fixity/infix.hs b/data/examples/declaration/signature/fixity/infix.hs
--- a/data/examples/declaration/signature/fixity/infix.hs
+++ b/data/examples/declaration/signature/fixity/infix.hs
@@ -1,2 +1,4 @@
 infix 0 <?>
 infix 9 <^-^>
+
+infix 2 ->
diff --git a/data/examples/declaration/value/function/primitive-literals-four-out.hs b/data/examples/declaration/value/function/primitive-literals-four-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/value/function/primitive-literals-four-out.hs
@@ -0,0 +1,10 @@
+{-# LANGUAGE ExtendedLiterals #-}
+{-# LANGUAGE MagicHash #-}
+
+foo = 1#
+
+bar = 2##
+
+baz = 3#Word32
+
+baz = 0b1010#Int64
diff --git a/data/examples/declaration/value/function/primitive-literals-out.hs b/data/examples/declaration/value/function/primitive-literals-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/value/function/primitive-literals-out.hs
@@ -0,0 +1,10 @@
+{-# LANGUAGE ExtendedLiterals #-}
+{-# LANGUAGE MagicHash #-}
+
+foo = 1#
+
+bar = 2##
+
+baz = 3#Word32
+
+baz = 0b1010#Int64
diff --git a/data/examples/declaration/value/function/primitive-literals.hs b/data/examples/declaration/value/function/primitive-literals.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/declaration/value/function/primitive-literals.hs
@@ -0,0 +1,9 @@
+{-# LANGUAGE ExtendedLiterals, MagicHash #-}
+
+foo = 1#
+
+bar = 2##
+
+baz = 3#Word32
+
+baz =  0b1010#Int64
diff --git a/data/examples/declaration/warning/warning-single-line-four-out.hs b/data/examples/declaration/warning/warning-single-line-four-out.hs
--- a/data/examples/declaration/warning/warning-single-line-four-out.hs
+++ b/data/examples/declaration/warning/warning-single-line-four-out.hs
@@ -11,3 +11,6 @@
 
 data Number = Number Dobule
 {-# DEPRECATED Number "Use Scientific instead." #-}
+
+head (a : _) = a
+{-# WARNING in "x-partial" head "This function is partial..." #-}
diff --git a/data/examples/declaration/warning/warning-single-line-out.hs b/data/examples/declaration/warning/warning-single-line-out.hs
--- a/data/examples/declaration/warning/warning-single-line-out.hs
+++ b/data/examples/declaration/warning/warning-single-line-out.hs
@@ -11,3 +11,6 @@
 
 data Number = Number Dobule
 {-# DEPRECATED Number "Use Scientific instead." #-}
+
+head (a : _) = a
+{-# WARNING in "x-partial" head "This function is partial..." #-}
diff --git a/data/examples/declaration/warning/warning-single-line.hs b/data/examples/declaration/warning/warning-single-line.hs
--- a/data/examples/declaration/warning/warning-single-line.hs
+++ b/data/examples/declaration/warning/warning-single-line.hs
@@ -13,3 +13,6 @@
 
 data Number = Number Dobule
 {-# DEPRECATED Number "Use Scientific instead." #-}
+
+head (a:_) = a
+{-# WARNING in "x-partial" head "This function is partial..." #-}
diff --git a/data/examples/import/deprecated-export-multi-line-four-out.hs b/data/examples/import/deprecated-export-multi-line-four-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-multi-line-four-out.hs
@@ -0,0 +1,6 @@
+module X (
+    {-# DEPRECATE D(D1) "D1 will not be exposed in a version 0.2 and later" #-}
+    D (D1, D2),
+) where
+
+data D = D1 | D2
diff --git a/data/examples/import/deprecated-export-multi-line-out.hs b/data/examples/import/deprecated-export-multi-line-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-multi-line-out.hs
@@ -0,0 +1,7 @@
+module X
+  ( {-# DEPRECATE D(D1) "D1 will not be exposed in a version 0.2 and later" #-}
+    D (D1, D2),
+  )
+where
+
+data D = D1 | D2
diff --git a/data/examples/import/deprecated-export-multi-line.hs b/data/examples/import/deprecated-export-multi-line.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-multi-line.hs
@@ -0,0 +1,5 @@
+module X
+    ( {-# DEPRECATE D(D1) "D1 will not be exposed in a version 0.2 and later" #-}
+      D(D1, D2)
+    ) where
+data D = D1 | D2
diff --git a/data/examples/import/deprecated-export-single-line-four-out.hs b/data/examples/import/deprecated-export-single-line-four-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-single-line-four-out.hs
@@ -0,0 +1,3 @@
+module A ({-# DEPRECATED "blah" #-} x) where
+
+x = True
diff --git a/data/examples/import/deprecated-export-single-line-out.hs b/data/examples/import/deprecated-export-single-line-out.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-single-line-out.hs
@@ -0,0 +1,3 @@
+module A ({-# DEPRECATED "blah" #-} x) where
+
+x = True
diff --git a/data/examples/import/deprecated-export-single-line.hs b/data/examples/import/deprecated-export-single-line.hs
new file mode 100644
--- /dev/null
+++ b/data/examples/import/deprecated-export-single-line.hs
@@ -0,0 +1,1 @@
+module A ( {-# DEPRECATED "blah" #-} x ) where { x = True }
diff --git a/data/fourmolu/column-limit/input-multi.hs b/data/fourmolu/column-limit/input-multi.hs
new file mode 100644
--- /dev/null
+++ b/data/fourmolu/column-limit/input-multi.hs
@@ -0,0 +1,91 @@
+-- Less than 80 characters
+import Data.List (head, isPrefixOf, tail)
+
+-- Over 80 characters, should break this line when column-limit is set to 80.
+import Data.Maybe (catMaybe, fromJust, fromMaybe, isJust, isNothing, listToMaybe, mapMaybe, maybe, maybeToList)
+
+-- For reference, this line had exactly 80 characters -------------------------|
+
+oneVeryLongLine :: [String]
+oneVeryLongLine = ["akjsndjklansdsad"] ++ ["jkanskdjnajsndjnasd"] ++ ["jknasdljknasdlnasdn"] ++ ["lajndljnasdlnasds"]
+
+oneVeryLongList :: [String]
+oneVeryLongList = ["akjsndjklansdsad", "jkanskdjnajsndjnasd", "jknasdljknasdlnasdn", "lajndljnasdlnasds"]
+
+data NewDataType = NewDataType {field1 :: String, field2 :: String, field3 :: String, field4 :: String}
+
+-- Test if the current line breaking still works normally, i.e. if the user
+-- breaks the line, fourmolu breaks and aligns the rest.
+data SecondDataType = SecondDataType {field1 :: String
+    , field2 :: String, field3 :: String, field4 :: String}
+
+data DataTypeWithAVeryLongName = DataTypeWithAVeryLongName String String String String String
+
+-- For reference, this line had exactly 80 characters -------------------------|
+
+{----- Long function signatures -----}
+
+longFunction0 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> [String]
+longFunction0 veryLongArg1 a b c d e f = ["a list", "of strings", "that will break the", "column limit"]
+
+longFunction1 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
+longFunction1
+    veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5 veryLongArg6 = undefined
+
+longFunction12 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5
+longFunction12 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> String
+    veryLongArg6 veryLongArg6 = undefined
+
+longFunction2 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
+longFunction2 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 a veryLongArg6 =
+    let aVeryLongLine = ["list one", "list one", "list one", "list one", "list one", "list one"]
+     in undefined
+
+longFunction3 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
+longFunction3 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5 veryLongArg6 = undefined
+
+-- For reference, this line had exactly 80 characters -------------------------|
+
+{-----  Known limitation: idempotence is broken -----}
+
+-- With the column-limit option set, fourmolu will not be idempotent in some
+-- cases. An example can be seen below, where the long line ends with a `do`.
+
+-- Original code
+testFund :: Maybe Int
+testFund =
+  firstTest oneFunctionArgument abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde $ do
+    result <- aRandomResult
+
+-- Will become this when formatted with column-limit set to 80.
+testFund :: Maybe Int
+testFund =
+    firstTest
+        oneFunctionArgument
+        abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde $ do
+        result <- aRandomResult
+
+-- Which, if formatted again, will become this:
+testFund :: Maybe Int
+testFund =
+    firstTest
+        oneFunctionArgument
+        abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde
+        $ do
+            result <- aRandomResult
+
+{- // -}
+
+{----- BlockArguments (https://github.com/fourmolu/fourmolu/issues/377) -----}
+
+
+{-# LANGUAGE BlockArguments #-}
+
+putThen :: String -> IO a -> IO a
+putThen s action =
+    putStrLn s >> action
+
+main :: IO ()
+main = do
+    putThen "012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789" do
+        putStrLn ""
diff --git a/data/fourmolu/column-limit/input.hs b/data/fourmolu/column-limit/input.hs
deleted file mode 100644
--- a/data/fourmolu/column-limit/input.hs
+++ /dev/null
@@ -1,82 +0,0 @@
-module ColumnLimitTest where
-
--- Less than 80 characters
-import Data.List (isPrefixOf, head, tail)
-
--- Over 80 characters, should break this line when column-limit is set to 80.
-import Data.Maybe (maybe, fromMaybe, fromJust, catMaybe, mapMaybe, isJust, isNothing, listToMaybe, maybeToList)
-
--- For reference, this line had exactly 80 characters -------------------------|
-
-oneVeryLongLine :: [String]
-oneVeryLongLine = ["akjsndjklansdsad"] ++ ["jkanskdjnajsndjnasd"] ++ ["jknasdljknasdlnasdn"] ++ ["lajndljnasdlnasds"]
-
-oneVeryLongList :: [String]
-oneVeryLongList = ["akjsndjklansdsad", "jkanskdjnajsndjnasd", "jknasdljknasdlnasdn", "lajndljnasdlnasds"]
-
-
-data NewDataType = NewDataType {field1 :: String, field2 :: String, field3 :: String, field4 :: String}
-
--- Test if the current line breaking still works normally, i.e. if the user
--- breaks the line, fourmolu breaks and aligns the rest.    
-data SecondDataType = SecondDataType {field1 :: String
-    , field2 :: String, field3 :: String, field4 :: String}
-
-data DataTypeWithAVeryLongName = DataTypeWithAVeryLongName String String String String String
-
-
--- Long function signatures
-
--- For reference, this line had exactly 80 characters -------------------------|
-
-longFunction0 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> [String]
-longFunction0 veryLongArg1 a b c d e f = ["a list", "of strings", "that will break the", "column limit"]
-
-longFunction1 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
-longFunction1 
-    veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5 veryLongArg6 = undefined
-
-longFunction12 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5 
-longFunction12 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> String
-    veryLongArg6 veryLongArg6 = undefined
-
-
-longFunction2 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
-longFunction2 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 a veryLongArg6 =
-    let aVeryLongLine = ["list one", "list one", "list one", "list one", "list one", "list one"]
-    in undefined
-
-longFunction3 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String
-longFunction3 veryLongArg1 veryLongArg2 veryLongArg3 veryLongArg4 veryLongArgument5 veryLongArg6 = undefined
-
-
--- For reference, this line had exactly 80 characters -------------------------|
-
--- ----------------  Known limitation: idempotence is broken ----------------
-
--- With the column-limit option set, fourmolu will not be idempotent in some
--- cases. An example can be seen below, where the long line ends with a `do`.
-
--- Original code
-testFund :: Maybe Int
-testFund = 
-  firstTest oneFunctionArgument abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde $ do
-    result <- aRandomResult
-
--- Will become this when formatted with column-limit set to 80.
-testFund :: Maybe Int
-testFund =
-    firstTest
-        oneFunctionArgument
-        abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde $ do
-        result <- aRandomResult
-
-
--- Which, if formatted again, will become this:
-testFund :: Maybe Int
-testFund =
-    firstTest
-        oneFunctionArgument
-        abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde
-        $ do
-            result <- aRandomResult
diff --git a/data/fourmolu/column-limit/output-limit=100.hs b/data/fourmolu/column-limit/output-limit=100.hs
--- a/data/fourmolu/column-limit/output-limit=100.hs
+++ b/data/fourmolu/column-limit/output-limit=100.hs
@@ -1,5 +1,3 @@
-module ColumnLimitTest where
-
 -- Less than 80 characters
 import Data.List (head, isPrefixOf, tail)
 
@@ -38,10 +36,10 @@
 
 data DataTypeWithAVeryLongName = DataTypeWithAVeryLongName String String String String String
 
--- Long function signatures
-
 -- For reference, this line had exactly 80 characters -------------------------|
 
+{----- Long function signatures -----}
+
 longFunction0 ::
     String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> [String]
 longFunction0 veryLongArg1 a b c d e f = ["a list", "of strings", "that will break the", "column limit"]
@@ -78,7 +76,7 @@
 
 -- For reference, this line had exactly 80 characters -------------------------|
 
--- ----------------  Known limitation: idempotence is broken ----------------
+{-----  Known limitation: idempotence is broken -----}
 
 -- With the column-limit option set, fourmolu will not be idempotent in some
 -- cases. An example can be seen below, where the long line ends with a `do`.
@@ -106,3 +104,19 @@
         abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde
         $ do
             result <- aRandomResult
+
+{- // -}
+
+{----- BlockArguments (https://github.com/fourmolu/fourmolu/issues/377) -----}
+{-# LANGUAGE BlockArguments #-}
+
+putThen :: String -> IO a -> IO a
+putThen s action =
+    putStrLn s >> action
+
+main :: IO ()
+main = do
+    putThen
+        "012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789"
+        do
+            putStrLn ""
diff --git a/data/fourmolu/column-limit/output-limit=80.hs b/data/fourmolu/column-limit/output-limit=80.hs
--- a/data/fourmolu/column-limit/output-limit=80.hs
+++ b/data/fourmolu/column-limit/output-limit=80.hs
@@ -1,5 +1,3 @@
-module ColumnLimitTest where
-
 -- Less than 80 characters
 import Data.List (head, isPrefixOf, tail)
 
@@ -48,10 +46,10 @@
 data DataTypeWithAVeryLongName
     = DataTypeWithAVeryLongName String String String String String
 
--- Long function signatures
-
 -- For reference, this line had exactly 80 characters -------------------------|
 
+{----- Long function signatures -----}
+
 longFunction0 ::
     String ->
     String ->
@@ -103,7 +101,7 @@
 
 -- For reference, this line had exactly 80 characters -------------------------|
 
--- ----------------  Known limitation: idempotence is broken ----------------
+{-----  Known limitation: idempotence is broken -----}
 
 -- With the column-limit option set, fourmolu will not be idempotent in some
 -- cases. An example can be seen below, where the long line ends with a `do`.
@@ -133,3 +131,19 @@
         abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde
         $ do
             result <- aRandomResult
+
+{- // -}
+
+{----- BlockArguments (https://github.com/fourmolu/fourmolu/issues/377) -----}
+{-# LANGUAGE BlockArguments #-}
+
+putThen :: String -> IO a -> IO a
+putThen s action =
+    putStrLn s >> action
+
+main :: IO ()
+main = do
+    putThen
+        "012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789"
+        do
+            putStrLn ""
diff --git a/data/fourmolu/column-limit/output-limit=none.hs b/data/fourmolu/column-limit/output-limit=none.hs
--- a/data/fourmolu/column-limit/output-limit=none.hs
+++ b/data/fourmolu/column-limit/output-limit=none.hs
@@ -1,5 +1,3 @@
-module ColumnLimitTest where
-
 -- Less than 80 characters
 import Data.List (head, isPrefixOf, tail)
 
@@ -27,10 +25,10 @@
 
 data DataTypeWithAVeryLongName = DataTypeWithAVeryLongName String String String String String
 
--- Long function signatures
-
 -- For reference, this line had exactly 80 characters -------------------------|
 
+{----- Long function signatures -----}
+
 longFunction0 :: String -> String -> String -> Maybe Int -> Maybe Int -> Maybe Int -> String -> [String]
 longFunction0 veryLongArg1 a b c d e f = ["a list", "of strings", "that will break the", "column limit"]
 
@@ -66,7 +64,7 @@
 
 -- For reference, this line had exactly 80 characters -------------------------|
 
--- ----------------  Known limitation: idempotence is broken ----------------
+{-----  Known limitation: idempotence is broken -----}
 
 -- With the column-limit option set, fourmolu will not be idempotent in some
 -- cases. An example can be seen below, where the long line ends with a `do`.
@@ -94,3 +92,17 @@
         abcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcdeabcde
         $ do
             result <- aRandomResult
+
+{- // -}
+
+{----- BlockArguments (https://github.com/fourmolu/fourmolu/issues/377) -----}
+{-# LANGUAGE BlockArguments #-}
+
+putThen :: String -> IO a -> IO a
+putThen s action =
+    putStrLn s >> action
+
+main :: IO ()
+main = do
+    putThen "012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789" do
+        putStrLn ""
diff --git a/data/fourmolu/import-export/input-multi.hs b/data/fourmolu/import-export/input-multi.hs
--- a/data/fourmolu/import-export/input-multi.hs
+++ b/data/fourmolu/import-export/input-multi.hs
@@ -40,3 +40,13 @@
   ( -- | asdf
     singleExport
   ) where
+
+{- // -}
+
+-- https://github.com/fourmolu/fourmolu/issues/381
+module Foo (
+    -- * Re-export of module
+    module X,
+    -- * Some other thing
+    Foo,
+) where
diff --git a/data/fourmolu/import-export/output-ImportExportDiffFriendly.hs b/data/fourmolu/import-export/output-ImportExportDiffFriendly.hs
--- a/data/fourmolu/import-export/output-ImportExportDiffFriendly.hs
+++ b/data/fourmolu/import-export/output-ImportExportDiffFriendly.hs
@@ -39,3 +39,14 @@
     -- | asdf
     singleExport,
 ) where
+
+{- // -}
+
+-- https://github.com/fourmolu/fourmolu/issues/381
+module Foo (
+    -- * Re-export of module
+    module X,
+
+    -- * Some other thing
+    Foo,
+) where
diff --git a/data/fourmolu/import-export/output-ImportExportLeading.hs b/data/fourmolu/import-export/output-ImportExportLeading.hs
--- a/data/fourmolu/import-export/output-ImportExportLeading.hs
+++ b/data/fourmolu/import-export/output-ImportExportLeading.hs
@@ -39,3 +39,14 @@
     ( -- | asdf
       singleExport
     ) where
+
+{- // -}
+
+-- https://github.com/fourmolu/fourmolu/issues/381
+module Foo
+    ( -- * Re-export of module
+      module X
+
+      -- * Some other thing
+    , Foo
+    ) where
diff --git a/data/fourmolu/import-export/output-ImportExportTrailing.hs b/data/fourmolu/import-export/output-ImportExportTrailing.hs
--- a/data/fourmolu/import-export/output-ImportExportTrailing.hs
+++ b/data/fourmolu/import-export/output-ImportExportTrailing.hs
@@ -39,3 +39,14 @@
     ( -- | asdf
       singleExport,
     ) where
+
+{- // -}
+
+-- https://github.com/fourmolu/fourmolu/issues/381
+module Foo
+    ( -- * Re-export of module
+      module X,
+
+      -- * Some other thing
+      Foo,
+    ) where
diff --git a/data/fourmolu/single-constraint-parens/input.hs b/data/fourmolu/single-constraint-parens/input.hs
--- a/data/fourmolu/single-constraint-parens/input.hs
+++ b/data/fourmolu/single-constraint-parens/input.hs
@@ -6,3 +6,6 @@
 
 -- https://github.com/fourmolu/fourmolu/issues/340
 quantifiedConstraint :: (forall a. Show a => Show (f a)) => f Int
+
+-- https://github.com/fourmolu/fourmolu/issues/374
+nestedConstraint :: ((c a, c b) => c (f a b)) => Is c a -> Is c b -> Is c (f a b)
diff --git a/data/fourmolu/single-constraint-parens/output-ConstraintAlways.hs b/data/fourmolu/single-constraint-parens/output-ConstraintAlways.hs
--- a/data/fourmolu/single-constraint-parens/output-ConstraintAlways.hs
+++ b/data/fourmolu/single-constraint-parens/output-ConstraintAlways.hs
@@ -5,3 +5,5 @@
 functionName2 :: (C a, D a) => a
 -- https://github.com/fourmolu/fourmolu/issues/340
 quantifiedConstraint :: (forall a. (Show a) => Show (f a)) => f Int
+-- https://github.com/fourmolu/fourmolu/issues/374
+nestedConstraint :: ((c a, c b) => c (f a b)) => Is c a -> Is c b -> Is c (f a b)
diff --git a/data/fourmolu/single-constraint-parens/output-ConstraintAuto.hs b/data/fourmolu/single-constraint-parens/output-ConstraintAuto.hs
--- a/data/fourmolu/single-constraint-parens/output-ConstraintAuto.hs
+++ b/data/fourmolu/single-constraint-parens/output-ConstraintAuto.hs
@@ -5,3 +5,5 @@
 functionName2 :: (C a, D a) => a
 -- https://github.com/fourmolu/fourmolu/issues/340
 quantifiedConstraint :: (forall a. Show a => Show (f a)) => f Int
+-- https://github.com/fourmolu/fourmolu/issues/374
+nestedConstraint :: ((c a, c b) => c (f a b)) => Is c a -> Is c b -> Is c (f a b)
diff --git a/data/fourmolu/single-constraint-parens/output-ConstraintNever.hs b/data/fourmolu/single-constraint-parens/output-ConstraintNever.hs
--- a/data/fourmolu/single-constraint-parens/output-ConstraintNever.hs
+++ b/data/fourmolu/single-constraint-parens/output-ConstraintNever.hs
@@ -5,3 +5,5 @@
 functionName2 :: (C a, D a) => a
 -- https://github.com/fourmolu/fourmolu/issues/340
 quantifiedConstraint :: (forall a. Show a => Show (f a)) => f Int
+-- https://github.com/fourmolu/fourmolu/issues/374
+nestedConstraint :: ((c a, c b) => c (f a b)) => Is c a -> Is c b -> Is c (f a b)
diff --git a/fourmolu.cabal b/fourmolu.cabal
--- a/fourmolu.cabal
+++ b/fourmolu.cabal
@@ -1,13 +1,13 @@
 cabal-version:      2.4
 name:               fourmolu
-version:            0.14.0.0
+version:            0.14.1.0
 license:            BSD-3-Clause
 license-file:       LICENSE.md
 maintainer:
     Matt Parsons <parsonsmatt@gmail.com>
     George Thomas <georgefsthomas@gmail.com>
     Brandon Chinn <brandonchinn178@gmail.com>
-tested-with:        ghc ==9.2.8 ghc ==9.4.5 ghc ==9.6.2
+tested-with:        ghc ==9.4.7 ghc ==9.6.3 ghc ==9.8.1
 homepage:           https://github.com/fourmolu/fourmolu
 bug-reports:        https://github.com/fourmolu/fourmolu/issues
 synopsis:           A formatter for Haskell source code
@@ -106,23 +106,23 @@
     default-language: GHC2021
     build-depends:
         Cabal-syntax >=3.10 && <3.11,
-        Diff >=0.4 && <1.0,
+        Diff >=0.4 && <1,
         MemoTrie >=0.6 && <0.7,
         ansi-terminal >=0.10 && <1.1,
         array >=0.5 && <0.6,
-        base >=4.14 && <5.0,
+        base >=4.14 && <5,
         binary >=0.8 && <0.9,
         bytestring >=0.2 && <0.13,
-        containers >=0.5 && <0.7,
+        containers >=0.5 && <0.8,
         deepseq >=1.4 && <1.6,
         directory ^>=1.3,
         file-embed >=0.0.15 && <0.1,
         filepath >=1.2 && <1.5,
-        ghc-lib-parser >=9.6 && <9.7,
-        megaparsec >=9.0,
-        mtl >=2.0 && <3.0,
+        ghc-lib-parser >=9.8 && <9.9,
+        megaparsec >=9,
+        mtl >=2 && <3,
         syb >=0.7 && <0.8,
-        text >=2.0 && <3.0,
+        text >=2 && <3,
         -- fourmolu-only deps
         aeson >=1.0 && <3.0,
         scientific >=0.3.2 && <1,
@@ -147,13 +147,13 @@
     default-language: GHC2021
     build-depends:
         Cabal-syntax >=3.10 && <3.11,
-        base >=4.12 && <5.0,
+        base >=4.12 && <5,
         containers >=0.5 && <0.7,
         directory ^>=1.3,
         filepath >=1.2 && <1.5,
-        ghc-lib-parser >=9.6 && <9.7,
+        ghc-lib-parser >=9.8 && <9.9,
         optparse-applicative >=0.14 && <0.19,
-        text >=2.0 && <3.0,
+        text >=2 && <3,
         th-env >=0.1.1 && <0.2,
         -- fourmolu-only deps
         directory >=1.3.3 && <1.4,
@@ -171,7 +171,7 @@
 test-suite tests
     type:               exitcode-stdio-1.0
     main-is:            Spec.hs
-    build-tool-depends: hspec-discover:hspec-discover >=2.0 && <3.0
+    build-tool-depends: hspec-discover:hspec-discover >=2 && <3
     hs-source-dirs:     tests
     other-modules:
         Ormolu.CabalInfoSpec
@@ -189,18 +189,18 @@
     build-depends:
         Cabal-syntax >=3.10 && <3.11,
         QuickCheck >=2.14,
-        base >=4.14 && <5.0,
+        base >=4.14 && <5,
         containers >=0.5 && <0.7,
         directory ^>=1.3,
         filepath >=1.2 && <1.5,
-        ghc-lib-parser >=9.6 && <9.7,
-        hspec >=2.0 && <3.0,
+        ghc-lib-parser >=9.8 && <9.9,
+        hspec >=2 && <3,
         hspec-megaparsec >=2.2,
-        megaparsec >=9.0,
+        megaparsec >=9,
         path >=0.6 && <0.10,
-        path-io >=1.4.2 && <2.0,
+        path-io >=1.4.2 && <2,
         temporary ^>=1.3,
-        text >=2.0 && <3.0
+        text >=2 && <3
 
     -- specific to fourmolu tests
     other-modules:
diff --git a/src/Ormolu.hs b/src/Ormolu.hs
--- a/src/Ormolu.hs
+++ b/src/Ormolu.hs
@@ -53,8 +53,10 @@
 import Data.Text (Text)
 import Data.Text qualified as T
 import Debug.Trace
-import GHC.Driver.CmdLine qualified as GHC
+import GHC.Driver.Errors.Types
+import GHC.Types.Error
 import GHC.Types.SrcLoc
+import GHC.Utils.Error
 import Ormolu.Config
 import Ormolu.Diff.ParseResult
 import Ormolu.Diff.Text
@@ -102,8 +104,9 @@
   (warnings, result0) <-
     parseModule' cfg fixityMap OrmoluParsingFailed path originalInput
   when (cfgDebug cfg) $ do
-    forM_ warnings $ \(GHC.Warn reason (L loc msg)) ->
-      traceM $ unwords ["*** WARNING ***", showOutputable loc, msg, showOutputable reason]
+    forM_ warnings $ \driverMsg -> do
+      let driverMsgSDoc = formatBulleted $ diagnosticMessage defaultOpts driverMsg
+      traceM $ unwords ["*** WARNING ***", showOutputable driverMsgSDoc]
     forM_ result0 $ \case
       ParsedSnippet r -> do
         let CommentStream comments = prCommentStream r
@@ -250,7 +253,7 @@
   FilePath ->
   -- | Actual input for the parser
   Text ->
-  m ([GHC.Warn], [SourceSnippet])
+  m (DriverMessages, [SourceSnippet])
 parseModule' cfg fixityMap mkException path str = do
   (warnings, r) <- parseModule cfg fixityMap path str
   case r of
diff --git a/src/Ormolu/Fixity/Imports.hs b/src/Ormolu/Fixity/Imports.hs
--- a/src/Ormolu/Fixity/Imports.hs
+++ b/src/Ormolu/Fixity/Imports.hs
@@ -16,7 +16,7 @@
 import Distribution.ModuleName (ModuleName)
 import Distribution.Types.PackageName
 import GHC.Data.FastString qualified as GHC
-import GHC.Hs hiding (ModuleName)
+import GHC.Hs hiding (ModuleName, OpName)
 import GHC.Types.Name.Occurrence
 import GHC.Types.PkgQual (RawPkgQual (..))
 import GHC.Types.SourceText (StringLiteral (..))
diff --git a/src/Ormolu/Imports.hs b/src/Ormolu/Imports.hs
--- a/src/Ormolu/Imports.hs
+++ b/src/Ormolu/Imports.hs
@@ -133,7 +133,7 @@
     isPrelude = moduleNameString moduleName == "Prelude"
     moduleName = unLoc ideclName
 
--- | Normalize a collection of import\/export items.
+-- | Normalize a collection of import items.
 normalizeLies :: [LIE GhcPs] -> [LIE GhcPs]
 normalizeLies = sortOn (getIewn . unLoc) . M.elems . foldl' combine M.empty
   where
@@ -149,21 +149,21 @@
             Nothing -> Just . L new_l $
               case new of
                 IEThingWith _ n wildcard g ->
-                  IEThingWith EpAnnNotUsed n wildcard (normalizeWNames g)
+                  IEThingWith (Nothing, EpAnnNotUsed) n wildcard (normalizeWNames g)
                 other -> other
             Just old ->
               let f = \case
-                    IEVar _ n -> IEVar NoExtField n
+                    IEVar _ n -> IEVar Nothing n
                     IEThingAbs _ _ -> new
-                    IEThingAll _ n -> IEThingAll EpAnnNotUsed n
+                    IEThingAll _ n -> IEThingAll (Nothing, EpAnnNotUsed) n
                     IEThingWith _ n wildcard g ->
                       case new of
-                        IEVar NoExtField _ ->
+                        IEVar _ _ ->
                           error "Ormolu.Imports broken presupposition"
                         IEThingAbs _ _ ->
-                          IEThingWith EpAnnNotUsed n wildcard g
+                          IEThingWith (Nothing, EpAnnNotUsed) n wildcard g
                         IEThingAll _ n' ->
-                          IEThingAll EpAnnNotUsed n'
+                          IEThingAll (Nothing, EpAnnNotUsed) n'
                         IEThingWith _ n' wildcard' g' ->
                           let combinedWildcard =
                                 case (wildcard, wildcard') of
@@ -171,7 +171,7 @@
                                   (_, IEWildcard _) -> IEWildcard 0
                                   _ -> NoIEWildcard
                            in IEThingWith
-                                EpAnnNotUsed
+                                (Nothing, EpAnnNotUsed)
                                 n'
                                 combinedWildcard
                                 (normalizeWNames (g <> g'))
@@ -197,7 +197,7 @@
 -- | Project @'IEWrappedName' 'GhcPs'@ from @'IE' 'GhcPs'@.
 getIewn :: IE GhcPs -> IEWrappedNameOrd
 getIewn = \case
-  IEVar NoExtField x -> IEWrappedNameOrd (unLoc x)
+  IEVar _ x -> IEWrappedNameOrd (unLoc x)
   IEThingAbs _ x -> IEWrappedNameOrd (unLoc x)
   IEThingAll _ x -> IEWrappedNameOrd (unLoc x)
   IEThingWith _ x _ _ -> IEWrappedNameOrd (unLoc x)
diff --git a/src/Ormolu/Parser.hs b/src/Ormolu/Parser.hs
--- a/src/Ormolu/Parser.hs
+++ b/src/Ormolu/Parser.hs
@@ -30,7 +30,6 @@
 import GHC.Data.FastString qualified as GHC
 import GHC.Data.Maybe (orElse)
 import GHC.Data.StringBuffer (StringBuffer)
-import GHC.Driver.CmdLine qualified as GHC
 import GHC.Driver.Config.Parser (initParserOpts)
 import GHC.Driver.Errors.Types qualified as GHC
 import GHC.Driver.Session as GHC
@@ -46,7 +45,6 @@
 import GHC.Types.SrcLoc
 import GHC.Utils.Error
 import GHC.Utils.Exception (ExceptionMonad)
-import GHC.Utils.Outputable (defaultSDocContext)
 import GHC.Utils.Panic qualified as GHC
 import Ormolu.Config
 import Ormolu.Config.Gen (SingleConstraintParens (..))
@@ -72,7 +70,7 @@
   -- | Input for parser
   Text ->
   m
-    ( [GHC.Warn],
+    ( GHC.DriverMessages,
       Either (SrcSpan, String) [SourceSnippet]
     )
 parseModule config@Config {..} packageFixityMap path rawInput = liftIO $ do
@@ -136,7 +134,7 @@
                   Nothing -> ""
                 msg =
                   showOutputable
-                    . formatBulleted defaultSDocContext
+                    . formatBulleted
                     . diagnosticMessage GHC.NoDiagnosticOpts
                     $ err
          in case L.sortOn (rateSeverity . errMsgSeverity) errs of
@@ -217,6 +215,7 @@
     patchContext = fmap $ \case
       [x@(L _ (HsParTy _ inner))]
         | L _ HsForAllTy {} <- inner -> [x]
+        | L _ HsQualTy {} <- inner -> [x]
         | ConstraintNever <- constraintParens -> [inner]
         | otherwise -> [x]
       [x@(L lx _)]
@@ -262,7 +261,8 @@
     LinearTypes, -- steals the (%) type operator in some cases
     OverloadedRecordDot, -- f.g parses differently
     OverloadedRecordUpdate, -- qualified fields are not supported
-    OverloadedLabels -- a#b is parsed differently
+    OverloadedLabels, -- a#b is parsed differently
+    ExtendedLiterals -- 1#Word32 is parsed differently
   ]
 
 -- | Run a 'GHC.P' computation.
@@ -297,7 +297,7 @@
   FilePath ->
   -- | Input for parser
   StringBuffer ->
-  IO (Either String ([GHC.Warn], DynFlags))
+  IO (Either String (GHC.DriverMessages, DynFlags))
 parsePragmasIntoDynFlags flags extraOpts filepath input =
   catchGhcErrors $ do
     let (_warnings, fileOpts) =
diff --git a/src/Ormolu/Printer/Combinators.hs b/src/Ormolu/Printer/Combinators.hs
--- a/src/Ormolu/Printer/Combinators.hs
+++ b/src/Ormolu/Printer/Combinators.hs
@@ -32,6 +32,7 @@
     located',
     switchLayout,
     switchLayoutNoLimit,
+    spansLayout,
     Layout (..),
     vlayout,
     getLayout,
@@ -97,7 +98,7 @@
 import Data.Text (Text)
 import GHC.Data.Strict qualified as Strict
 import GHC.LanguageExtensions.Type
-import GHC.Types.SrcLoc
+import GHC.Types.SrcLoc hiding (spans)
 import Ormolu.Config
 import Ormolu.Printer.Comments
 import Ormolu.Printer.Internal
@@ -168,48 +169,44 @@
 -- provided by GHC AST. It is relatively rare that this one is needed.
 --
 -- Given empty list this function will set layout to single line.
-switchLayout' ::
-  -- | Should enforce column limit, if one is set
-  Bool ->
+switchLayout ::
   -- | Span that controls layout
   [SrcSpan] ->
   -- | Computation to run with changed layout
   R () ->
   R ()
-switchLayout' useColLimit spans' r = do
-  columnLimit <-
-    if useColLimit then getPrinterOpt poColumnLimit else pure NoLimit
-  enterLayout (spansLayout columnLimit spans') r
-
-switchLayout :: [SrcSpan] -> R () -> R ()
-switchLayout = switchLayout' True
+switchLayout spans r = do
+  layout <- spansLayout spans
+  enterLayout layout r
 
--- | Switch layout version that disregards the column limit.
+-- | Same as 'switchLayout', except disregards the column limit.
+--
 -- It should be used for the argument list in function definitions because
 -- the column limit can't be enforced there without changing the AST.
 switchLayoutNoLimit :: [SrcSpan] -> R () -> R ()
-switchLayoutNoLimit = switchLayout' False
+switchLayoutNoLimit spans = enterLayout (spansLayoutWithLimit NoLimit spans)
 
 -- | Which layout combined spans result in?
-spansLayout :: ColumnLimit -> [SrcSpan] -> Layout
-spansLayout colLimit = \case
+spansLayout :: [SrcSpan] -> R Layout
+spansLayout spans = do
+  colLimit <- getPrinterOpt poColumnLimit
+  pure $ spansLayoutWithLimit colLimit spans
+
+spansLayoutWithLimit :: ColumnLimit -> [SrcSpan] -> Layout
+spansLayoutWithLimit colLimit = \case
   [] -> SingleLine
   (x : xs) ->
-    if isOneLineSpan combinedSpan && not (shouldBreakSingleLine combinedSpan)
-      then SingleLine
-      else MultiLine
-    where
-      combinedSpan = foldr combineSrcSpans x xs
-
-      shouldBreakSingleLine :: SrcSpan -> Bool
-      shouldBreakSingleLine (RealSrcSpan rs _) =
-        case colLimit of
-          ColumnLimit maxLineLength ->
-            spanLineLength > fromIntegral maxLineLength
-          NoLimit -> False
-        where
-          spanLineLength = srcSpanEndCol rs - srcSpanStartCol rs
-      shouldBreakSingleLine _ = False
+    let combinedSpan = foldr combineSrcSpans x xs
+     in if isOneLineSpan combinedSpan && not (shouldBreakSingleLine combinedSpan)
+          then SingleLine
+          else MultiLine
+  where
+    shouldBreakSingleLine srcSpan =
+      case (srcSpan, colLimit) of
+        (RealSrcSpan rs _, ColumnLimit maxLineLength) ->
+          let spanLineLength = srcSpanEndCol rs - srcSpanStartCol rs
+           in spanLineLength > fromIntegral maxLineLength
+        _ -> False
 
 -- | Insert a space if enclosing layout is single-line, or newline if it's
 -- multiline.
diff --git a/src/Ormolu/Printer/Meat/Common.hs b/src/Ormolu/Printer/Meat/Common.hs
--- a/src/Ormolu/Printer/Meat/Common.hs
+++ b/src/Ormolu/Printer/Meat/Common.hs
@@ -19,6 +19,7 @@
 import Control.Monad
 import Data.Foldable (traverse_)
 import Data.Text qualified as T
+import GHC.Data.FastString
 import GHC.Hs.Doc
 import GHC.Hs.Extension (GhcPs)
 import GHC.Hs.ImpExp
@@ -72,6 +73,8 @@
           NameAnn {nann_adornment = NameParens} ->
             parens N . handleUnboxedSumsAndHashInteraction
           NameAnn {nann_adornment = NameBackquotes} -> backticks
+          -- whether the `->` identifier is parenthesized
+          NameAnnRArrow {nann_mopen = Just _} -> parens N
           -- special case for unboxed unit tuples
           NameAnnOnly {nann_adornment = NameParensHash} -> const $ txt "(# #)"
           _ -> id
@@ -248,4 +251,4 @@
 p_sourceText :: SourceText -> R ()
 p_sourceText = \case
   NoSourceText -> pure ()
-  SourceText s -> txt (T.pack s)
+  SourceText s -> atom @FastString s
diff --git a/src/Ormolu/Printer/Meat/Declaration.hs b/src/Ormolu/Printer/Meat/Declaration.hs
--- a/src/Ormolu/Printer/Meat/Declaration.hs
+++ b/src/Ormolu/Printer/Meat/Declaration.hs
@@ -139,7 +139,9 @@
     p_dataDecl
       Associated
       tcdLName
-      (tyVarsToTyPats tcdTyVars)
+      (hsq_explicit tcdTyVars)
+      getLocA
+      (located' p_hsTyVarBndr)
       tcdFixity
       tcdDataDefn
   ClassDecl {..} ->
diff --git a/src/Ormolu/Printer/Meat/Declaration/Data.hs b/src/Ormolu/Printer/Meat/Declaration/Data.hs
--- a/src/Ormolu/Printer/Meat/Declaration/Data.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/Data.hs
@@ -26,21 +26,25 @@
 import Ormolu.Printer.Combinators
 import Ormolu.Printer.Meat.Common
 import Ormolu.Printer.Meat.Type
-import Ormolu.Utils (matchAddEpAnn)
+import Ormolu.Utils
 
 p_dataDecl ::
   -- | Whether to format as data family
   FamilyStyle ->
   -- | Type constructor
   LocatedN RdrName ->
-  -- | Type patterns
-  HsTyPats GhcPs ->
+  -- | Type variables
+  [tyVar] ->
+  -- | Get location information for type variables
+  (tyVar -> SrcSpan) ->
+  -- | How to print type variables
+  (tyVar -> R ()) ->
   -- | Lexical fixity
   LexicalFixity ->
   -- | Data definition
   HsDataDefn GhcPs ->
   R ()
-p_dataDecl style name tpats fixity HsDataDefn {..} = do
+p_dataDecl style name tyVars getTyVarLoc p_tyVar fixity HsDataDefn {..} = do
   txt $ case dd_cons of
     NewTypeCon _ -> "newtype"
     DataTypeCons False _ -> "data"
@@ -59,7 +63,7 @@
       space
       p_sourceText type_
       txt " #-}"
-  let constructorSpans = getLocA name : fmap lhsTypeArgSrcSpan tpats
+  let constructorSpans = getLocA name : fmap getTyVarLoc tyVars
       sigSpans = maybeToList . fmap getLocA $ dd_kindSig
       declHeaderSpans =
         maybeToList (getLocA <$> dd_ctxt) ++ constructorSpans ++ sigSpans
@@ -78,7 +82,7 @@
           (isInfix fixity)
           True
           (p_rdrName name)
-          (p_lhsTypeArg <$> tpats)
+          (p_tyVar <$> tyVars)
       forM_ dd_kindSig $ \k -> do
         space
         token'dcolon
diff --git a/src/Ormolu/Printer/Meat/Declaration/Instance.hs b/src/Ormolu/Printer/Meat/Declaration/Instance.hs
--- a/src/Ormolu/Printer/Meat/Declaration/Instance.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/Instance.hs
@@ -97,7 +97,14 @@
 
 p_dataFamInstDecl :: FamilyStyle -> DataFamInstDecl GhcPs -> R ()
 p_dataFamInstDecl style (DataFamInstDecl {dfid_eqn = FamEqn {..}}) =
-  p_dataDecl style feqn_tycon feqn_pats feqn_fixity feqn_rhs
+  p_dataDecl
+    style
+    feqn_tycon
+    feqn_pats
+    lhsTypeArgSrcSpan
+    p_lhsTypeArg
+    feqn_fixity
+    feqn_rhs
 
 match_overlap_mode :: Maybe (LocatedP OverlapMode) -> R () -> R ()
 match_overlap_mode overlap_mode layoutStrategy =
diff --git a/src/Ormolu/Printer/Meat/Declaration/OpTree.hs b/src/Ormolu/Printer/Meat/Declaration/OpTree.hs
--- a/src/Ormolu/Printer/Meat/Declaration/OpTree.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/OpTree.hs
@@ -15,6 +15,8 @@
 where
 
 import Data.Functor ((<&>))
+import Data.List.NonEmpty (NonEmpty (..))
+import Data.List.NonEmpty qualified as NE
 import GHC.Hs
 import GHC.Types.Fixity
 import GHC.Types.Name (occNameString)
@@ -82,7 +84,7 @@
 -- | Convert a 'LHsExpr' containing an operator tree to the 'OpTree'
 -- intermediate representation.
 exprOpTree :: LHsExpr GhcPs -> OpTree (LHsExpr GhcPs) (LHsExpr GhcPs)
-exprOpTree (L _ (OpApp _ x op y)) = OpBranches [exprOpTree x, exprOpTree y] [op]
+exprOpTree (L _ (OpApp _ x op y)) = BinaryOpBranches (exprOpTree x) op (exprOpTree y)
 exprOpTree n = OpNode n
 
 -- | Print an operator tree where leaves are values.
@@ -94,17 +96,15 @@
   OpTree (LHsExpr GhcPs) (OpInfo (LHsExpr GhcPs)) ->
   R ()
 p_exprOpTree s (OpNode x) = located x (p_hsExpr' NotApplicand s)
-p_exprOpTree s t@(OpBranches exprs ops) = do
-  let firstExpr = head exprs
-      otherExprs = tail exprs
-      placement =
+p_exprOpTree s t@(OpBranches exprs@(firstExpr :| otherExprs) ops) = do
+  let placement =
         opBranchPlacement
           exprPlacement
           firstExpr
           (last otherExprs)
       rightMostNode = \case
         n@(OpNode _) -> n
-        OpBranches exprs'' _ -> rightMostNode (last exprs'')
+        OpBranches exprs'' _ -> rightMostNode (NE.last exprs'')
       isDoBlock = \case
         OpNode (L _ (HsDo _ ctx _)) -> case ctx of
           DoExpr _ -> True
@@ -128,7 +128,7 @@
           && not (isDoBlock $ rightMostNode prevExpr)
       -- If all operators at the current level match the conditions to be
       -- trailing, then put them in a trailing position
-      isTrailing = all couldBeTrailing $ zip exprs ops
+      isTrailing = all couldBeTrailing $ zip (NE.toList exprs) ops
   ub <- if isTrailing then return useBraces else opBranchBraceStyle placement
   indent <- getPrinterOpt poIndentation
   let p_x = ub $ p_exprOpTree s firstExpr
@@ -183,7 +183,7 @@
 cmdOpTree :: LHsCmdTop GhcPs -> OpTree (LHsCmdTop GhcPs) (LHsExpr GhcPs)
 cmdOpTree = \case
   (L _ (HsCmdTop _ (L _ (HsCmdArrForm _ op Infix _ [x, y])))) ->
-    OpBranches [cmdOpTree x, cmdOpTree y] [op]
+    BinaryOpBranches (cmdOpTree x) op (cmdOpTree y)
   n -> OpNode n
 
 -- | Print an operator tree where leaves are commands.
@@ -195,10 +195,8 @@
   OpTree (LHsCmdTop GhcPs) (OpInfo (LHsExpr GhcPs)) ->
   R ()
 p_cmdOpTree s (OpNode x) = located x (p_hsCmdTop s)
-p_cmdOpTree s t@(OpBranches exprs ops) = do
-  let firstExpr = head exprs
-      otherExprs = tail exprs
-      placement =
+p_cmdOpTree s t@(OpBranches (firstExpr :| otherExprs) ops) = do
+  let placement =
         opBranchPlacement
           cmdTopPlacement
           firstExpr
@@ -230,7 +228,7 @@
 -- intermediate representation.
 tyOpTree :: LHsType GhcPs -> OpTree (LHsType GhcPs) (LocatedN RdrName)
 tyOpTree (L _ (HsOpTy _ _ l op r)) =
-  OpBranches [tyOpTree l, tyOpTree r] [op]
+  BinaryOpBranches (tyOpTree l) op (tyOpTree r)
 tyOpTree n = OpNode n
 
 -- | Print an operator tree where leaves are types.
@@ -240,10 +238,8 @@
   OpTree (LHsType GhcPs) (OpInfo (LocatedN RdrName)) ->
   R ()
 p_tyOpTree (OpNode n) = located n p_hsType
-p_tyOpTree t@(OpBranches exprs ops) = do
-  let firstExpr = head exprs
-      otherExprs = tail exprs
-      placement =
+p_tyOpTree t@(OpBranches (firstExpr :| otherExprs) ops) = do
+  let placement =
         opBranchPlacement
           tyOpPlacement
           firstExpr
diff --git a/src/Ormolu/Printer/Meat/Declaration/Value.hs b/src/Ormolu/Printer/Meat/Declaration/Value.hs
--- a/src/Ormolu/Printer/Meat/Declaration/Value.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/Value.hs
@@ -34,6 +34,7 @@
 import Data.Text qualified as Text
 import Data.Void
 import GHC.Data.Bag (bagToList)
+import GHC.Data.FastString
 import GHC.Data.Strict qualified as Strict
 import GHC.Hs
 import GHC.LanguageExtensions.Type (Extension (NegativeLiterals))
@@ -352,7 +353,7 @@
       inci (sequence_ (intersperse breakpoint (located' (p_hsCmdTop N) <$> cmds)))
   HsCmdArrForm _ form Infix _ [left, right] -> do
     modFixityMap <- askModuleFixityMap
-    let opTree = OpBranches [cmdOpTree left, cmdOpTree right] [form]
+    let opTree = BinaryOpBranches (cmdOpTree left) form (cmdOpTree right)
     p_cmdOpTree
       s
       (reassociateOpTree (getOpName . unLoc) modFixityMap opTree)
@@ -643,12 +644,11 @@
         initSpan =
           combineSrcSpans' $
             getLocA f :| [(srcLocSpan . srcSpanStart . getLocA) lastp]
-        -- Hang the last argument only if the initial arguments span one
-        -- line.
-        placement =
-          if isOneLineSpan initSpan
-            then exprPlacement (unLoc lastp)
-            else Normal
+    -- Hang the last argument only if the initial arguments span one line.
+    placement <-
+      spansLayout [initSpan] <&> \case
+        SingleLine -> exprPlacement (unLoc lastp)
+        MultiLine -> Normal
     -- If the last argument is not hanging, just separate every argument as
     -- usual. If it is hanging, print the initial arguments and hang the
     -- last one. Also, use braces around the every argument except the last
@@ -699,7 +699,7 @@
       located (hswc_body a) p_hsType
   OpApp _ x op y -> do
     modFixityMap <- askModuleFixityMap
-    let opTree = OpBranches [exprOpTree x, exprOpTree y] [op]
+    let opTree = BinaryOpBranches (exprOpTree x) op (exprOpTree y)
     p_exprOpTree
       s
       (reassociateOpTree (getOpName . unLoc) modFixityMap opTree)
@@ -812,11 +812,11 @@
               Ambiguous NoExtField n -> n
         p_recFields p_lbl =
           sep commaDel (sitcc . located' (p_hsFieldBind p_lbl))
-    inci . braces N $
-      either
-        (p_recFields p_updLbl)
-        (p_recFields $ located' $ coerce p_ldotFieldOccs)
-        rupd_flds
+    inci . braces N $ case rupd_flds of
+      RegularRecUpdFields {..} ->
+        p_recFields p_updLbl recUpdFields
+      OverloadedRecUpdFields {..} ->
+        p_recFields (located' (coerce p_ldotFieldOccs)) olRecUpdFields
   HsGetField {..} -> do
     located gf_expr p_hsExpr
     txt "."
@@ -1284,9 +1284,9 @@
           _ -> False
 
 -- | Print the source text of a string literal while indenting gaps correctly.
-p_stringLit :: String -> R ()
+p_stringLit :: FastString -> R ()
 p_stringLit src =
-  let s = splitGaps src
+  let s = splitGaps (unpackFS src)
       singleLine =
         txt $ Text.pack (mconcat s)
       multiLine =
@@ -1321,11 +1321,7 @@
     -- Attaches previous and next items to each list element
     zipPrevNext :: [a] -> [(Maybe a, a, Maybe a)]
     zipPrevNext xs =
-      let z =
-            zip
-              (zip (Nothing : map Just xs) xs)
-              (map Just (tail xs) ++ repeat Nothing)
-       in map (\((p, x), n) -> (p, x, n)) z
+      zip3 (Nothing : map Just xs) xs (map Just (drop 1 xs) ++ [Nothing])
     orig (_, x, _) = x
 
 ----------------------------------------------------------------------------
diff --git a/src/Ormolu/Printer/Meat/Declaration/Value.hs-boot b/src/Ormolu/Printer/Meat/Declaration/Value.hs-boot
--- a/src/Ormolu/Printer/Meat/Declaration/Value.hs-boot
+++ b/src/Ormolu/Printer/Meat/Declaration/Value.hs-boot
@@ -11,6 +11,7 @@
   )
 where
 
+import GHC.Data.FastString
 import GHC.Hs
 import Ormolu.Printer.Combinators
 
@@ -18,7 +19,7 @@
 p_pat :: Pat GhcPs -> R ()
 p_hsExpr :: HsExpr GhcPs -> R ()
 p_hsUntypedSplice :: SpliceDecoration -> HsUntypedSplice GhcPs -> R ()
-p_stringLit :: String -> R ()
+p_stringLit :: FastString -> R ()
 
 data IsApplicand
 
diff --git a/src/Ormolu/Printer/Meat/Declaration/Warning.hs b/src/Ormolu/Printer/Meat/Declaration/Warning.hs
--- a/src/Ormolu/Printer/Meat/Declaration/Warning.hs
+++ b/src/Ormolu/Printer/Meat/Declaration/Warning.hs
@@ -1,14 +1,16 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RecordWildCards #-}
 
 module Ormolu.Printer.Meat.Declaration.Warning
   ( p_warnDecls,
-    p_moduleWarning,
+    p_warningTxt,
   )
 where
 
 import Data.Foldable
 import Data.Text (Text)
+import Data.Text qualified as T
 import GHC.Hs
 import GHC.Types.Name.Reader
 import GHC.Types.SourceText
@@ -16,6 +18,7 @@
 import GHC.Unit.Module.Warnings
 import Ormolu.Printer.Combinators
 import Ormolu.Printer.Meat.Common
+import Ormolu.Utils
 
 p_warnDecls :: WarnDecls GhcPs -> R ()
 p_warnDecls (Warnings _ warnings) =
@@ -25,8 +28,8 @@
 p_warnDecl (Warning _ functions warningTxt) =
   p_topLevelWarning functions warningTxt
 
-p_moduleWarning :: WarningTxt GhcPs -> R ()
-p_moduleWarning wtxt = do
+p_warningTxt :: WarningTxt GhcPs -> R ()
+p_warningTxt wtxt = do
   let (pragmaText, lits) = warningText wtxt
   inci $ pragma pragmaText $ inci $ p_lits lits
 
@@ -41,7 +44,12 @@
 
 warningText :: WarningTxt GhcPs -> (Text, [Located StringLiteral])
 warningText = \case
-  WarningTxt _ lits -> ("WARNING", fmap hsDocString <$> lits)
+  WarningTxt mcat _ lits -> ("WARNING" <> T.pack cat, fmap hsDocString <$> lits)
+    where
+      cat = case unLoc <$> mcat of
+        Just InWarningCategory {..} ->
+          " in " <> show (showOutputable @WarningCategory (unLoc iwc_wc))
+        Nothing -> ""
   DeprecatedTxt _ lits -> ("DEPRECATED", fmap hsDocString <$> lits)
 
 p_lits :: [Located StringLiteral] -> R ()
diff --git a/src/Ormolu/Printer/Meat/ImportExport.hs b/src/Ormolu/Printer/Meat/ImportExport.hs
--- a/src/Ormolu/Printer/Meat/ImportExport.hs
+++ b/src/Ormolu/Printer/Meat/ImportExport.hs
@@ -10,6 +10,7 @@
 where
 
 import Control.Monad
+import Data.Foldable (for_)
 import Data.List (inits)
 import Data.Text qualified as T
 import GHC.Hs
@@ -19,6 +20,7 @@
 import Ormolu.Config
 import Ormolu.Printer.Combinators
 import Ormolu.Printer.Meat.Common
+import Ormolu.Printer.Meat.Declaration.Warning
 import Ormolu.Utils (RelativePos (..), attachRelativePos)
 
 p_hsmodExports :: [LIE GhcPs] -> R ()
@@ -77,7 +79,10 @@
 
 p_lie :: Layout -> Bool -> RelativePos -> IE GhcPs -> R ()
 p_lie encLayout isAllPrevDoc relativePos = \case
-  IEVar NoExtField l1 ->
+  IEVar mwarn l1 -> do
+    for_ mwarn $ \warnTxt -> do
+      located warnTxt p_warningTxt
+      breakpoint
     withComma $
       located l1 p_ieWrappedName
   IEThingAbs _ l1 ->
@@ -99,8 +104,9 @@
           IEWildcard n ->
             let (before, after) = splitAt n names
              in before ++ [txt ".."] ++ after
-  IEModuleContents _ l1 -> withComma $ do
-    indentDoc $ located l1 p_hsmodName
+  IEModuleContents _ l1 ->
+    withComma $
+      located l1 p_hsmodName
   IEGroup NoExtField n str -> do
     case relativePos of
       SinglePos -> return ()
diff --git a/src/Ormolu/Printer/Meat/Module.hs b/src/Ormolu/Printer/Meat/Module.hs
--- a/src/Ormolu/Printer/Meat/Module.hs
+++ b/src/Ormolu/Printer/Meat/Module.hs
@@ -70,7 +70,7 @@
 
   forM_ hsmodDeprecMessage $ \w -> do
     breakpoint
-    located' p_moduleWarning w
+    located' p_warningTxt w
 
   isRespectful <- getPrinterOpt poRespectful
   isDiffFriendly <- (== ImportExportDiffFriendly) <$> getPrinterOpt poImportExportStyle
diff --git a/src/Ormolu/Printer/Meat/Type.hs b/src/Ormolu/Printer/Meat/Type.hs
--- a/src/Ormolu/Printer/Meat/Type.hs
+++ b/src/Ormolu/Printer/Meat/Type.hs
@@ -16,7 +16,6 @@
     p_conDeclFields,
     p_lhsTypeArg,
     p_hsSigType,
-    tyVarsToTyPats,
     hsOuterTyVarBndrsToHsType,
     lhsTypeToSigType,
   )
@@ -85,7 +84,7 @@
       breakpoint
       inci $
         sep breakpoint (located' p_hsType) args
-  HsAppKindTy _ ty kd -> sitcc $ do
+  HsAppKindTy _ ty _ kd -> sitcc $ do
     -- The first argument is the location of the "@..." part. Not 100% sure,
     -- but I think we can ignore it as long as we use 'located' on both the
     -- type and the kind.
@@ -122,7 +121,7 @@
       sep (space >> txt "|" >> breakpoint) (sitcc . located' p_hsType) xs
   HsOpTy _ _ x op y -> do
     modFixityMap <- askModuleFixityMap
-    let opTree = OpBranches [tyOpTree x, tyOpTree y] [op]
+    let opTree = BinaryOpBranches (tyOpTree x) op (tyOpTree y)
     p_tyOpTree
       (reassociateOpTree (Just . unLoc) modFixityMap opTree)
   HsParTy _ t ->
@@ -263,24 +262,35 @@
   [x] -> located x p_hsType
   xs -> parens N $ sep commaDel (sitcc . located' p_hsType) xs
 
-class IsInferredTyVarBndr flag where
+class IsTyVarBndrFlag flag where
   isInferred :: flag -> Bool
+  p_tyVarBndrFlag :: flag -> R ()
+  p_tyVarBndrFlag _ = pure ()
 
-instance IsInferredTyVarBndr () where
+instance IsTyVarBndrFlag () where
   isInferred () = False
 
-instance IsInferredTyVarBndr Specificity where
+instance IsTyVarBndrFlag Specificity where
   isInferred = \case
     InferredSpec -> True
     SpecifiedSpec -> False
 
-p_hsTyVarBndr :: (IsInferredTyVarBndr flag) => HsTyVarBndr flag GhcPs -> R ()
+instance IsTyVarBndrFlag (HsBndrVis GhcPs) where
+  isInferred _ = False
+  p_tyVarBndrFlag = \case
+    HsBndrRequired -> pure ()
+    HsBndrInvisible _ -> txt "@"
+
+p_hsTyVarBndr :: (IsTyVarBndrFlag flag) => HsTyVarBndr flag GhcPs -> R ()
 p_hsTyVarBndr = \case
-  UserTyVar _ flag x ->
+  UserTyVar _ flag x -> do
+    p_tyVarBndrFlag flag
     (if isInferred flag then braces N else id) $ p_rdrName x
-  KindedTyVar _ flag l k -> (if isInferred flag then braces else parens) N . sitcc $ do
-    located l atom
-    inci $ startTypeAnnotation k p_hsType
+  KindedTyVar _ flag l k -> do
+    p_tyVarBndrFlag flag
+    (if isInferred flag then braces else parens) N . sitcc $ do
+      located l atom
+      inci $ startTypeAnnotation k p_hsType
 
 data ForAllVisibility = ForAllInvis | ForAllVis
 
@@ -356,21 +366,6 @@
 
 ----------------------------------------------------------------------------
 -- Conversion functions
-
-tyVarToType :: HsTyVarBndr () GhcPs -> HsType GhcPs
-tyVarToType = \case
-  UserTyVar _ () tvar -> HsTyVar EpAnnNotUsed NotPromoted tvar
-  KindedTyVar _ () tvar kind ->
-    -- Note: we always add parentheses because for whatever reason GHC does
-    -- not use HsParTy for left-hand sides of declarations. Please see
-    -- <https://gitlab.haskell.org/ghc/ghc/issues/17404>. This is fine as
-    -- long as 'tyVarToType' does not get applied to right-hand sides of
-    -- declarations.
-    HsParTy EpAnnNotUsed . noLocA $
-      HsKindSig EpAnnNotUsed (noLocA (HsTyVar EpAnnNotUsed NotPromoted tvar)) kind
-
-tyVarsToTyPats :: LHsQTyVars GhcPs -> HsTyPats GhcPs
-tyVarsToTyPats HsQTvs {..} = HsValArg . fmap tyVarToType <$> hsq_explicit
 
 -- could be generalized to also handle () instead of Specificity
 hsOuterTyVarBndrsToHsType ::
diff --git a/src/Ormolu/Printer/Operators.hs b/src/Ormolu/Printer/Operators.hs
--- a/src/Ormolu/Printer/Operators.hs
+++ b/src/Ormolu/Printer/Operators.hs
@@ -1,9 +1,11 @@
 {-# LANGUAGE MultiWayIf #-}
+{-# LANGUAGE PatternSynonyms #-}
 
 -- | This module helps handle operator chains composed of different
 -- operators that may have different precedence and fixities.
 module Ormolu.Printer.Operators
   ( OpTree (..),
+    pattern BinaryOpBranches,
     OpInfo (..),
     opTreeLoc,
     reassociateOpTree,
@@ -11,6 +13,7 @@
   )
 where
 
+import Data.List.NonEmpty (NonEmpty (..))
 import Data.List.NonEmpty qualified as NE
 import GHC.Types.Name.Reader
 import GHC.Types.SrcLoc
@@ -31,9 +34,12 @@
   | -- | A subtree of operator application(s); the invariant is: @length
     -- exprs == length ops + 1@. @OpBranches [x, y, z] [op1, op2]@
     -- represents the expression @x op1 y op2 z@.
-    OpBranches [OpTree ty op] [op]
+    OpBranches (NonEmpty (OpTree ty op)) [op]
   deriving (Eq, Show)
 
+pattern BinaryOpBranches :: OpTree ty op -> op -> OpTree ty op -> OpTree ty op
+pattern BinaryOpBranches x op y = OpBranches (x :| [y]) [op]
+
 -- | Wrapper for an operator, carrying information about its name and
 -- fixity.
 data OpInfo op = OpInfo
@@ -78,7 +84,7 @@
 opTreeLoc :: (HasSrcSpan l) => OpTree (GenLocated l a) b -> SrcSpan
 opTreeLoc (OpNode n) = getLoc' n
 opTreeLoc (OpBranches exprs _) =
-  combineSrcSpans' . NE.fromList . fmap opTreeLoc $ exprs
+  combineSrcSpans' . fmap opTreeLoc $ exprs
 
 -- | Re-associate an 'OpTree' taking into account precedence of operators.
 -- Users are expected to first construct an initial 'OpTree', then
@@ -129,11 +135,11 @@
   OpBranches rExprs rOps
   where
     makeFlatOpTree' expr = case makeFlatOpTree expr of
-      OpNode n -> ([OpNode n], [])
+      OpNode n -> (NE.singleton (OpNode n), [])
       OpBranches noptExprs noptOps -> (noptExprs, noptOps)
     flattenedSubTrees = makeFlatOpTree' <$> exprs
-    rExprs = concatMap fst flattenedSubTrees
-    rOps = concat $ interleave (snd <$> flattenedSubTrees) (pure <$> ops)
+    rExprs = fst =<< flattenedSubTrees
+    rOps = concat $ interleave (snd <$> NE.toList flattenedSubTrees) (pure <$> ops)
     interleave (x : xs) (y : ys) = x : y : interleave xs ys
     interleave [] ys = ys
     interleave xs [] = xs
@@ -239,7 +245,7 @@
     --   [ex0 op0 ex1 op1 ex2 op2 ex3 op3 ex4 op4 ex5 op5 ex6 op6 ex7]
     -- into
     --   [ex0 op0 [ex1 op1 ex2] op2 [ex3 op3 ex4 op4 ex5] op5 [ex6 op6 ex7]]
-    splitTree nExprs nOps indices = go nExprs nOps indices 0 [] [] [] []
+    splitTree nExprs nOps indices = go (NE.toList nExprs) nOps indices 0 [] [] [] []
       where
         go ::
           -- Remaining exprs to look up
@@ -267,15 +273,15 @@
           -- expr in the subExprs bag, so we build a subtree (if necessary)
           -- with sub-bags, add the node/subtree to the result bag, and then
           -- emit the result tree
-          let resExpr = buildFromSub subExprs subOps
-           in OpBranches (reverse (resExpr : resExprs)) (reverse resOps)
+          let resExpr = buildFromSub (NE.fromList subExprs) subOps
+           in OpBranches (NE.reverse (resExpr :| resExprs)) (reverse resOps)
         go (x : xs) (o : os) (idx : idxs) i subExprs subOps resExprs resOps
           | i == idx =
               -- The op we are looking at is one on which we need to split.
               -- So we build a subtree from the sub-bags and the current
               -- expr, append it to the result exprs, and continue with
               -- cleared sub-bags
-              let resExpr = buildFromSub (x : subExprs) subOps
+              let resExpr = buildFromSub (x :| subExprs) subOps
                in go xs os idxs (i + 1) [] [] (resExpr : resExprs) (o : resOps)
         go (x : xs) ops idxs i subExprs subOps resExprs resOps =
           -- Either there is no op left, or the op we are looking at is not
@@ -288,7 +294,7 @@
     --   [ex0 op0 ex1 op1 ex2 op2 ex3 op3 ex4 op4 ex5 op5 ex6 op6 ex7]
     -- into
     --   [[ex0 op0 ex1 op1 ex2] op2 ex3 op3 [ex4 op4 ex5] op5 ex6 op6 ex7]
-    groupTree nExprs nOps indices = go nExprs nOps indices 0 [] [] [] []
+    groupTree nExprs nOps indices = go (NE.toList nExprs) nOps indices 0 [] [] [] []
       where
         go ::
           -- remaining exprs to look up
@@ -316,11 +322,10 @@
           -- empty. If it is not, we build a subtree (if necessary) with
           -- sub-bags and add the resulting node/subtree to the result bag.
           -- In any case, we then emit the result tree
-          let resExprs' =
-                if null subExprs
-                  then resExprs
-                  else buildFromSub subExprs subOps : resExprs
-           in OpBranches (reverse resExprs') (reverse resOps)
+          let resExprs' = case NE.nonEmpty subExprs of
+                Nothing -> NE.fromList resExprs
+                Just subExprs' -> buildFromSub subExprs' subOps :| resExprs
+           in OpBranches (NE.reverse resExprs') (reverse resOps)
         go (x : xs) (o : os) (idx : idxs) i subExprs subOps resExprs resOps
           | i == idx =
               -- The op we are looking at is one on which we need to group.
@@ -333,7 +338,7 @@
           -- the current expr, to form a subtree which is then added to the
           -- result bag.
           let (ops', resOps') = moveOneIfPossible ops resOps
-              resExpr = buildFromSub (x : subExprs) subOps
+              resExpr = buildFromSub (x :| subExprs) subOps
            in go xs ops' idxs (i + 1) [] [] (resExpr : resExprs) resOps'
         go (x : xs) ops idxs i [] subOps resExprs resOps =
           -- Either there is no op left, or the op we are looking at is not
@@ -349,8 +354,8 @@
     buildFromSub subExprs subOps = reassociateFlatOpTree $ case subExprs of
       -- Do not build a subtree when the potential subtree would have
       -- 1 expr(s) and 0 op(s)
-      [x] -> x
-      _ -> OpBranches (reverse subExprs) (reverse subOps)
+      x :| [] -> x
+      _ -> OpBranches (NE.reverse subExprs) (reverse subOps)
 
 -- | Indicate if an operator has @'InfixR' 0@ fixity. We special-case this
 -- class of operators because they often have, like ('$'), a specific
diff --git a/tests/Ormolu/Config/PrinterOptsSpec.hs b/tests/Ormolu/Config/PrinterOptsSpec.hs
--- a/tests/Ormolu/Config/PrinterOptsSpec.hs
+++ b/tests/Ormolu/Config/PrinterOptsSpec.hs
@@ -86,7 +86,7 @@
         },
       TestGroup
         { label = "column-limit",
-          isMulti = False,
+          isMulti = True,
           testCases = [NoLimit, ColumnLimit 80, ColumnLimit 100],
           updateConfig = \columnLimit opts -> opts {poColumnLimit = pure columnLimit},
           showTestCase = show,
diff --git a/tests/Ormolu/OpTreeSpec.hs b/tests/Ormolu/OpTreeSpec.hs
--- a/tests/Ormolu/OpTreeSpec.hs
+++ b/tests/Ormolu/OpTreeSpec.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE OverloadedLists #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 module Ormolu.OpTreeSpec (spec) where