Respect inline configs that happen to appear deep in AST

comments between top-level decls should be considered
for inline-config. But despite being placed between
top-level decls, occasionally they get connected
somewhere nested inside the AST of the first decl.
We fix this by extracting such comments in a
pre-processing step. The control flow was significantly
altered to allow for this;
before:
  parsing -> extract inline configs
          -> compute final config(s)
          -> split module into head/decls/comments/whitespace
          -> ... bridoc -> transformations -> printing
after:
  parsing -> split module into head/decl/comments/whitespace
          -> extract inline configs respecting comments that
             got extracted from decls in the previous step
          -> compute final config(s)
          -> ... bridoc -> transformations -> printing

brittany.cabal

@@ -170,6 +170,8 @@ test-suite brittany-test-suite
 
   build-depends:
     , hspec >= 2.8.3 && < 2.10
+    , HUnit >= 1.6.2 && < 1.7
+    , ansi-terminal >= 0.11.4 && < 0.12
     , parsec ^>= 3.1.14
     , these ^>= 1.1
   hs-source-dirs: source/test-suite

data/15-regressions.blt

@@ -329,7 +329,9 @@ func =
                                         foooooooooooooooooooooooooooooooo
 
 #test opapp-specialcasing-3
-func = fooooooooooooooooooooooooooooooooo + foooooooooooooooooooooooooooooooo
+func =
+  fooooooooooooooooooooooooooooooooo
+    + foooooooooooooooooooooooooooooooo
         [ foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
@@ -956,3 +958,43 @@ func = other $ meep
   [q|hello
      world|]
   (some other very long linnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnne)
+
+#test multiline-lambda-whitespace
+func =
+  Text.intercalate
+    "\n"
+    (   (\(abc, def) ->
+           abc ++ def ++ "lkajsdljkasdlkjasldjkljkasd" ++ asdasdasdasd
+        )
+    <$> mylist
+    )
+
+#test operator newline behaviour
+func =
+  fromIntegral aaaaaaaaaaaaaaaaaaa
+    / fromIntegral (aaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbb)
+
+#test multi-constructor associated data decl
+data POtfuggj
+instance BMGuwigoc POtfuggj where
+  data KVeeweknc POtfuggj r
+    = ILpieakli
+    | USilcnhkYaraposqu (WeyOoovf (Nubwlhtjd EculdW.QaeopznkAc r))
+    deriving stock (Lirylfj1, Jexr)
+    deriving anyclass Qart2.Vrzxuvcf
+
+#test bang-type
+data LabeledBool = LabeledBool !Int !Bool
+
+#test block-comment after let
+func = do
+  let cipInuihz = Vuozczdm.yhEfun tuhiuRasohy
+  let {- CAZEB mecwbd "Caa ||" -}
+      doeeRbaviceQzymin a b = olivhuwqbaq
+      iqnz biwomeJhhujy _ _ | biwomeJhhujy < volpoqAsizmHdwpl = pure 0
+  pure True
+
+#test comment-inside-decl
+func False = 0
+-- comment
+func True  = 1

data/30-tests-context-free.blt

@@ -1278,7 +1278,9 @@ func =
         foooooooooooooooooooooooooooooooo
 
 #test opapp-specialcasing-3
-func = fooooooooooooooooooooooooooooooooo + foooooooooooooooooooooooooooooooo
+func =
+  fooooooooooooooooooooooooooooooooo
+    + foooooooooooooooooooooooooooooooo
         [ foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo

source/library/Language/Haskell/Brittany/Internal.hs

@@ -10,6 +10,8 @@ module Language.Haskell.Brittany.Internal
    -- re-export from utils:
   , extractCommentConfigs
   , TraceFunc(TraceFunc)
+  , Splitting.splitModuleDecls
+  , Splitting.extractDeclMap
   )
 where
 
@@ -17,7 +19,6 @@ import           Control.Monad.Trans.Except
 import           Data.CZipWith
 import qualified Data.Text                     as Text
 import qualified Data.Text.Lazy                as TextL
-import qualified GHC                     hiding ( parseModule )
 import qualified GHC.Driver.Session            as GHC
 import           GHC.Hs
 import qualified GHC.LanguageExtensions.Type   as GHC
@@ -29,6 +30,8 @@ import           Language.Haskell.Brittany.Internal.S3_ToBriDocTools
 import           Language.Haskell.Brittany.Internal.Prelude
 import qualified Language.Haskell.Brittany.Internal.S1_Parsing
                                                as Parsing
+import qualified Language.Haskell.Brittany.Internal.S2_SplitModule
+                                               as Splitting
 import           Language.Haskell.Brittany.Internal.StepOrchestrate
                                                 ( processModule )
 import           Language.Haskell.Brittany.Internal.Types
@@ -79,9 +82,13 @@ parsePrintModule traceFunc configWithDebugs inputText = runExceptT $ do
     case parseResult of
       Left  err -> throwE [ErrorInput err]
       Right x   -> pure x
+  let moduleElementList = Splitting.splitModuleDecls parsedSource
   (inlineConf, perItemConf) <-
     mapExceptT (fmap $ bimap (\(a, b) -> [ErrorMacroConfig a b]) id)
-      $ extractCommentConfigs (useTraceFunc traceFunc) parsedSource
+      $ extractCommentConfigs
+        (useTraceFunc traceFunc)
+        (Splitting.extractDeclMap parsedSource)
+        moduleElementList
   let moduleConfig = cZipWith fromOptionIdentity config inlineConf
   let disableFormatting =
         moduleConfig & _conf_disable_formatting & confUnpack
@@ -96,11 +103,12 @@ parsePrintModule traceFunc configWithDebugs inputText = runExceptT $ do
                 & _econf_omit_output_valid_check
                 & confUnpack
         (ews, outRaw) <- if hasCPP || omitCheck
-          then lift $ processModule traceFunc moduleConfig perItemConf parsedSource
+          then lift
+            $ processModule traceFunc moduleConfig perItemConf moduleElementList
           else lift $ pPrintModuleAndCheck traceFunc
                                            moduleConfig
                                            perItemConf
-                                           parsedSource
+                                           moduleElementList
         let hackF s = fromMaybe s
               $ TextL.stripPrefix (TextL.pack "-- BRITANY_INCLUDE_HACK ") s
         pure $ if hackAroundIncludes
@@ -134,17 +142,17 @@ pPrintModuleAndCheck
   :: TraceFunc
   -> Config
   -> PerItemConfig
-  -> GHC.ParsedSource
+  -> FinalList ModuleElement p
   -> IO ([BrittanyError], TextL.Text)
-pPrintModuleAndCheck traceFunc conf inlineConf parsedModule = do
+pPrintModuleAndCheck traceFunc conf inlineConf moduleElementList = do
   let ghcOptions     = conf & _conf_forward & _options_ghc & runIdentity
-  (errs, output) <- processModule traceFunc conf inlineConf parsedModule
+  (errs, output) <- processModule traceFunc conf inlineConf moduleElementList
   parseResult <- Parsing.parseModuleFromString ghcOptions
                                                "output"
                                                (\_ -> return $ Right ())
                                                (TextL.unpack output)
   let errs' = errs ++ case parseResult of
-        Left{}  -> [ErrorOutputCheck]
+        Left x  -> [ErrorOutputCheck x]
         Right{} -> []
   return (errs', output)
 
@@ -162,10 +170,14 @@ parsePrintModuleTests conf filename input = do
   case parseResult of
     Left  err               -> return $ Left err
     Right (parsedModule, _) -> runExceptT $ do
+      let moduleElementList = Splitting.splitModuleDecls parsedModule
       (inlineConf, perItemConf) <-
         mapExceptT
           (fmap (bimap (\(a, _) -> "when parsing inline config: " ++ a) id))
-          $ extractCommentConfigs (\_ -> pure ()) parsedModule
+          $ extractCommentConfigs
+            (\_ -> pure ())
+            (Splitting.extractDeclMap parsedModule)
+            moduleElementList
       let moduleConf = cZipWith fromOptionIdentity conf inlineConf
       let omitCheck =
             conf
@@ -176,11 +188,11 @@ parsePrintModuleTests conf filename input = do
         then lift $ processModule (TraceFunc $ \_ -> pure ())
                                    moduleConf
                                    perItemConf
-                                   parsedModule
+                                   moduleElementList
         else lift $ pPrintModuleAndCheck (TraceFunc $ \_ -> pure ())
                                          moduleConf
                                          perItemConf
-                                         parsedModule
+                                         moduleElementList
       if null errs
         then pure $ TextL.toStrict $ ltext
         else throwE
@@ -195,7 +207,7 @@ parsePrintModuleTests conf filename input = do
     LayoutWarning str         -> str
     ErrorUnknownNode str _    -> str
     ErrorMacroConfig str _    -> "when parsing inline config: " ++ str
-    ErrorOutputCheck          -> "Output is not syntactically valid."
+    ErrorOutputCheck str      -> "Output is not syntactically valid: " ++ str
 -- this approach would for if there was a pure GHC.parseDynamicFilePragma.
 -- Unfortunately that does not exist yet, so we cannot provide a nominally
 -- pure interface.

source/library/Language/Haskell/Brittany/Internal/Components/Obfuscation.hs

@@ -64,6 +64,8 @@ keywords =
   , "proc"
   , "rec"
   , "family"
+  , "stock"
+  , "anyclass"
   ]
 
 extraKWs :: [String]

source/library/Language/Haskell/Brittany/Internal/Config/Config.hs

@@ -64,6 +64,7 @@ staticDefaultConfig = Config
     , _lconfig_fixityBasedAddAlignParens = coerce False
     , _lconfig_operatorParenthesisRefactorMode = coerce PRMKeep
     , _lconfig_operatorAllowUnqualify = coerce True
+    , _lconfig_allowSinglelineRecord = coerce True
     }
   , _conf_errorHandling = ErrorHandlingConfig
     { _econf_produceOutputOnErrors = coerce False
@@ -163,7 +164,7 @@ cmdlineConfigParser = do
       , _lconfig_allowSingleLineExportList = mempty
       , _lconfig_allowHangingQuasiQuotes = mempty
       , _lconfig_experimentalSemicolonNewlines = mempty
-      -- , _lconfig_allowSinglelineRecord     = mempty
+      , _lconfig_allowSinglelineRecord     = mempty
       , _lconfig_fixityAwareOps = mempty
       , _lconfig_fixityAwareTypeOps = mempty
       , _lconfig_fixityBasedAddAlignParens = mempty

source/library/Language/Haskell/Brittany/Internal/Config/InlineParsing.hs

@@ -26,7 +26,7 @@ import           Control.Monad.Trans.Except
 
 import           Language.Haskell.Brittany.Internal.Config.Config
 import           Language.Haskell.Brittany.Internal.Config.Types
-import Language.Haskell.Brittany.Internal.Util.AST
+import Language.Haskell.Brittany.Internal.Types
 import Language.Haskell.Brittany.Internal.Config.Types.Instances1 ()
 import Language.Haskell.Brittany.Internal.Config.Types.Instances2 ()
 -- import Language.Haskell.Brittany.Internal.Utils
@@ -44,46 +44,26 @@ data InlineConfigTarget
 
 extractCommentConfigs
   :: (String -> IO ())
-  -> GHC.ParsedSource
+  -> Map GHC.RealSrcSpan [String]
+  -> FinalList ModuleElement a
   -> ExceptT (String, String) IO (CConfig Maybe, PerItemConfig)
-extractCommentConfigs _putErrorLn modul = do
+extractCommentConfigs _putErrorLn declMap moduleElementList = do
-  let (L _ (GHC.HsModule modAnn _ _ _ _ decls _ _)) = modul
+  let comments = concatMapFinal (void moduleElementList) $ \case
-  let declMap :: Map GHC.RealSrcSpan [String]
+        MEExactModuleHead modul -> case GHC.hsmodAnn $ GHC.unLoc modul of
-      declMap = Map.fromList
-        [ ( case span of
-            GHC.RealSrcSpan s _ -> s
-            GHC.UnhelpfulSpan _ -> error "unexpected UnhelpfulSpan"
-          , getDeclBindingNames decl
-          )
-        | decl <- decls
-        , let (L (GHC.SrcSpanAnn _ span) _) = decl
-        ]
-  let epAnnComms = \case
           GHC.EpAnn _ _ (GHC.EpaComments prior) -> prior
           GHC.EpAnn _ _ (GHC.EpaCommentsBalanced prior following) ->
             prior ++ following
           GHC.EpAnnNotUsed -> []
-  let gatheredComments =
+        MEPrettyModuleHead{}   -> []
-        join
+        MEImportDecl{}         -> []
-          $ epAnnComms modAnn
+        MEDecl{}               -> []
-          : [ epAnnComms epAnn | L (GHC.SrcSpanAnn epAnn _) _x <- decls ]
+        MEComment (_, comment) -> [comment]
-  -- gatheredComments `forM_` \comm@(L anchor _) -> do
+        MEWhitespace{}         -> []
-  --   liftIO $ putErrorLn $ showOutputable comm
-  --   case Map.lookupLE (GHC.anchor anchor) declMap of
-  --     Nothing -> pure ()
-  --     Just (pos, le) -> do
-  --       liftIO $ putErrorLn $ "  le = " ++ show (toConstr le) ++ " at " ++ show
-  --         (ExactPrint.Utils.ss2deltaEnd pos (GHC.anchor anchor))
-  --   case Map.lookupGE (GHC.anchor anchor) declMap of
-  --     Nothing -> pure ()
-  --     Just (pos, ge) -> do
-  --       liftIO $ putErrorLn $ "  ge = " ++ show (toConstr ge) ++ " at " ++ show
-  --         (ExactPrint.Utils.ss2deltaStart (GHC.anchor anchor) pos)
   lineConfigs <- sequence
     [ case Butcher.runCmdParserSimpleString line2 parser of
         Left  err            -> throwE (err, line2)
         Right (target, conf) -> pure $ (GHC.anchor anchr, target, conf)
-    | L anchr (EpaComment comm _) <- gatheredComments
+    | L anchr (EpaComment comm _) <- comments
     , Just line1                  <- case comm of
       EpaLineComment l ->
         [ List.stripPrefix "-- BRITTANY" l

source/library/Language/Haskell/Brittany/Internal/Config/Types.hs

@@ -135,14 +135,14 @@ data CLayoutConfig f = LayoutConfig
     -- The implementation for this is a bit hacky and not tested; it might
     -- break output syntax or not work properly for every kind of brace. So
     -- far I have considered `do` and `case-of`.
-  -- , _lconfig_allowSinglelineRecord :: f (Last Bool)
+  , _lconfig_allowSinglelineRecord :: f (Last Bool)
-  --   -- if true, layouts record data decls as a single line when possible, e.g.
+    -- if true, layouts record data decls as a single line when possible, e.g.
-  --   -- > MyPoint { x :: Double, y :: Double }
+    -- > MyPoint { x :: Double, y :: Double }
-  --   -- if false, always use the multi-line layout
+    -- if false, always use the multi-line layout
-  --   -- > MyPoint
+    -- > MyPoint
-  --   -- >   { x :: Double
+    -- >   { x :: Double
-  --   -- >   , y :: Double
+    -- >   , y :: Double
-  --   -- >   }
+    -- >   }
   , _lconfig_fixityAwareOps :: f (Last Bool)
     -- enables fixity-based layouting, e.g.
     -- > foo =

source/library/Language/Haskell/Brittany/Internal/S2_SplitModule.hs

@@ -3,15 +3,17 @@
 -- TODO92
 
 module Language.Haskell.Brittany.Internal.S2_SplitModule
-  ( splitModule
+  ( extractDeclMap
-  )
+  , splitModuleDecls
-where
+  , splitModuleStart
+  ) where
 
 
 
 import           Language.Haskell.Brittany.Internal.Prelude
 
 import qualified Data.Generics                 as SYB
+import qualified Data.Map                      as Map
 import qualified GHC
 import           GHC                            ( AddEpAnn(AddEpAnn)
                                                 , Anchor(Anchor)
@@ -56,64 +58,49 @@ import           GHC.Parser.Annotation          ( DeltaPos
                                                   )
                                                 , EpaCommentTok(EpaEofComment)
                                                 )
-import           GHC.Types.SrcLoc               ( realSrcSpanEnd )
+import           GHC.Types.SrcLoc               ( realSrcSpanEnd
+                                                , realSrcSpanStart
+                                                )
 import qualified Language.Haskell.GHC.ExactPrint.Types
                                                as ExactPrint
 import qualified Language.Haskell.GHC.ExactPrint.Utils
                                                as ExactPrint
 import           Safe                           ( maximumMay )
+import qualified Control.Monad.Trans.Writer.Strict
+                                               as WriterS
 
 import           Language.Haskell.Brittany.Internal.Components.BriDoc
 import           Language.Haskell.Brittany.Internal.ToBriDoc.Module
 import           Language.Haskell.Brittany.Internal.Types
+import           Language.Haskell.Brittany.Internal.Util.AST
 
 
 
-splitModule
+extractDeclMap :: GHC.ParsedSource -> Map GHC.RealSrcSpan [String]
-  :: Bool
+extractDeclMap modul =
-  -> GHC.ParsedSource
+  Map.fromList
-  -> Maybe GHC.RealSrcLoc
+    [ ( case span of
-  -> FinalList ModuleElement ExactPrint.Pos
+          GHC.RealSrcSpan s _ -> s
-splitModule shouldReformatHead lmod posWhere = do
+          GHC.UnhelpfulSpan _ -> error "unexpected UnhelpfulSpan"
+      , getDeclBindingNames decl
+      )
+    | decl <- decls
+    , let (L (GHC.SrcSpanAnn _ span) _) = decl
+    ]
+  where (L _ (GHC.HsModule _ _ _ _ _ decls _ _)) = modul
+
+splitModuleDecls :: GHC.ParsedSource -> FinalList ModuleElement ExactPrint.Pos
+splitModuleDecls lmod = do
   let L moduleSpan modl          = lmod
-      HsModule _ _layout _name _exports imports decls _ _ = modl
+      HsModule _ _layout _name _exports _imports decls _ _ = modl
       (hsModAnn', finalComments) = case GHC.hsmodAnn modl of
         EpAnn a modAnns (EpaCommentsBalanced prior post) ->
           (EpAnn a modAnns (EpaCommentsBalanced prior []), post)
         _ -> (GHC.hsmodAnn modl, [])
-      moduleWithoutComments =
+      moduleWithoutComments = L moduleSpan modl { GHC.hsmodAnn   = hsModAnn'
-        L moduleSpan modl { GHC.hsmodAnn = hsModAnn', GHC.hsmodDecls = [] }
+                                                , GHC.hsmodDecls = []
-  lastSpan <- if shouldReformatHead
+                                                }
-    then do
+  lastSpan <- do
-      finalYield $ MEPrettyModuleHead moduleWithoutComments
-      let locBeforeImports =
-            maximumMay 
-              $  [ realSrcSpanEnd $ anchor a
-                 | L a _ <- case hsModAnn' of
-                   EpAnn _ _ (EpaComments cs             ) -> cs
-                   EpAnn _ _ (EpaCommentsBalanced cs1 cs2) -> cs1 ++ cs2
-                   EpAnnNotUsed -> error "unexpected EpAnnNotUsed"
-                 ]
-              ++ [ pos | Just pos <- [posWhere] ]
-      let (importLines, lastSpan) = finalToList $ transformToImportLine
-            ( maybe 0 srcLocLine locBeforeImports
-            , maybe 1 srcLocCol  locBeforeImports
-            )
-            imports
-      let commentedImports = groupifyImportLines importLines
-      sortCommentedImports commentedImports `forM_` \case
-        EmptyLines n ->
-          finalYield $ MEWhitespace $ DifferentLine n 1
-        SamelineComment{} ->
-          error "brittany internal error: splitModule SamelineComment"
-        NewlineComment  comm   -> finalYield $ MEComment comm
-        ImportStatement record -> do
-          forM_ (commentsBefore record) $ finalYield . MEComment
-          finalYield
-            $ MEImportDecl (importStatement record) (commentsSameline record)
-          forM_ (commentsAfter record) $ finalYield . MEComment
-      pure $ lastSpan
-    else do
     finalYield $ MEExactModuleHead moduleWithoutComments
     pure
       $  maybe (1, 1) (ExactPrint.ss2posEnd)
@@ -132,12 +119,43 @@ splitModule shouldReformatHead lmod posWhere = do
            EpAnnNotUsed                        -> []
          ]
       ++ [ span
-           | L (SrcSpanAnn _ (GHC.RealSrcSpan span _)) _ <- GHC.hsmodImports
+         | L (SrcSpanAnn _ (GHC.RealSrcSpan span _)) _ <- GHC.hsmodImports modl
-             modl
          ]
   spanAfterDecls <- enrichDecls lastSpan decls
   enrichComms spanAfterDecls finalComments
 
+splitModuleStart
+  :: GHC.ParsedSource
+  -> Maybe GHC.RealSrcLoc
+  -> FinalList ModuleElement ExactPrint.Pos
+splitModuleStart modul posWhere = do
+  finalYield $ MEPrettyModuleHead modul
+  let locBeforeImports =
+        maximumMay
+          $  [ realSrcSpanEnd $ anchor a
+             | L a _ <- case GHC.hsmodAnn $ unLoc modul of
+               EpAnn _ _ (EpaComments cs             ) -> cs
+               EpAnn _ _ (EpaCommentsBalanced cs1 cs2) -> cs1 ++ cs2
+               EpAnnNotUsed -> error "unexpected EpAnnNotUsed"
+             ]
+          ++ [ pos | Just pos <- [posWhere] ]
+  let (importLines, lastSpan) = finalToList $ transformToImportLine
+        ( maybe 0 srcLocLine locBeforeImports
+        , maybe 1 srcLocCol  locBeforeImports
+        )
+        (GHC.hsmodImports $ unLoc modul)
+  let commentedImports = groupifyImportLines importLines
+  sortCommentedImports commentedImports `forM_` \case
+    EmptyLines n -> finalYield $ MEWhitespace $ DifferentLine n 1
+    SamelineComment{} ->
+      error "brittany internal error: splitModuleStart SamelineComment"
+    NewlineComment  comm   -> finalYield $ MEComment comm
+    ImportStatement record -> do
+      forM_ (commentsBefore record) $ finalYield . MEComment
+      finalYield $ MEImportDecl (importStatement record)
+                                (commentsSameline record)
+      forM_ (commentsAfter record) $ finalYield . MEComment
+  pure $ lastSpan
 
 enrichComms
   :: ExactPrint.Pos -> [LEpaComment] -> FinalList ModuleElement ExactPrint.Pos
@@ -148,52 +166,57 @@ enrichComms lastSpanEnd = \case
       SameLine i        -> SameLine i
       DifferentLine l c -> DifferentLine (l - 1) c
     enrichComms (ExactPrint.ss2posEnd span) commRest
-  (L (Anchor span _) (EpaComment comm _) : commRest) -> do
+  lcomm@(L (Anchor span _) _) : commRest -> do
     case ExactPrint.ss2delta lastSpanEnd span of
       SameLine i -> do
-        finalYield $ MEComment (i, comm)
+        finalYield $ MEComment (i, lcomm)
       DifferentLine l c -> do
         finalYield $ MEWhitespace $ DifferentLine (l - 1) c
-        finalYield $ MEComment (0, comm)
+        finalYield $ MEComment (0, lcomm)
     enrichComms (ExactPrint.ss2posEnd span) commRest
 
 enrichDecls
   :: ExactPrint.Pos -> [LHsDecl GhcPs] -> FinalList ModuleElement ExactPrint.Pos
 enrichDecls lastSpanEnd = \case
   [] -> finalPure $ lastSpanEnd
-  (L (SrcSpanAnn dAnn rlspan@(GHC.RealSrcSpan span _)) decl : declRest) ->
+  ldecl@(L (SrcSpanAnn dAnn (GHC.RealSrcSpan span _)) _) : declRest ->
     case dAnn of
-      EpAnn dAnchor items (EpaComments dComments) -> do
+      EpAnn _dAnchor _items (EpaComments _dComments) -> do
         let
-          withoutComments =
+          commentExtract
-            (L (SrcSpanAnn (EpAnn dAnchor items (EpaComments [])) rlspan) decl)
+            :: [LEpaComment] -> WriterS.Writer [LEpaComment] [LEpaComment]
-          commentExtract = \case
+          commentExtract comms = do
-            L (GHC.Anchor anch _) EpaComment{} -> ExactPrint.ss2posEnd anch
+            let (innerComments, outerComments) =
-          -- It would be really nice if `ExactPrint.ss2posEnd span` was
+                  partition
-          -- sufficient. But for some reason the comments are not
+                    (\(L (Anchor anch _) _) ->
-          -- (consistently) included in the length of the anchor. I.e.
+                      (  realSrcSpanStart anch < realSrcSpanEnd span
-          -- there are cases where a syntax tree node has an anchor from
+                      && realSrcSpanEnd anch > realSrcSpanStart span
-          -- pos A -> pos B. But then somewhere _below_ that node is a
+                      )
-          -- comment that has an anchor pos B -> pos C.
+                    )
-          -- We simply detect this here.
+                    comms
-          -- We probably do some redundant `SYB.everything` lookups
+            WriterS.tell outerComments
-          -- throughout the code now. But optimizing it is not easy, and
+            pure innerComments
-          -- at worst it is larger constant factor on the size of the
+          (ldecl', extractedComments) = WriterS.runWriter
-          -- input, so it isn't _that_ bad.
+            $ SYB.everywhereM (SYB.mkM commentExtract) ldecl
-          fixedSpanEnd = SYB.everything
-            max
-            (SYB.mkQ (ExactPrint.ss2posEnd span) commentExtract)
-            decl
         case ExactPrint.ss2delta lastSpanEnd span of
           SameLine{} -> pure ()
           DifferentLine n _ ->
             finalYield $ MEWhitespace $ DifferentLine (n - 1) 1
-        let (afterComms, span2) = finalToList $ enrichComms fixedSpanEnd (reverse dComments)
+        let fixedSpanEnd = ExactPrint.ss2posEnd span
-        let (immediate, later) = List.span (\case
+        let (afterComms, span2) = finalToList
+              $ enrichComms fixedSpanEnd
+                            (List.sortOn (\(L l _) -> l) extractedComments)
+        let (immediate, later) =
+              List.span
+                (\case
                   MEComment{} -> True
                   _           -> False
-              ) afterComms
+                )
-        finalYield $ MEDecl withoutComments [ comm | MEComment comm <- immediate ]
+                afterComms
+        finalYield
+          $ MEDecl
+            ldecl'
+            [ (ind, GHC.ac_tok comm) | MEComment (ind, L _ comm) <- immediate ]
         later `forM_` finalYield
         enrichDecls span2 declRest
       EpAnn _anchor _items (EpaCommentsBalanced{}) ->
@@ -207,8 +230,8 @@ enrichDecls lastSpanEnd = \case
 
 data ImportLine
   = EmptyLines Int
-  | SamelineComment (Int, EpaCommentTok)
+  | SamelineComment (Int, LEpaComment)
-  | NewlineComment  (Int, EpaCommentTok) -- indentation and comment
+  | NewlineComment  (Int, LEpaComment) -- indentation and comment
   | ImportStatement ImportStatementRecord
 
 instance Show ImportLine where
@@ -221,10 +244,10 @@ instance Show ImportLine where
         (length $ commentsAfter r)
 
 data ImportStatementRecord = ImportStatementRecord
-  { commentsBefore   :: [(Int, EpaCommentTok)]
+  { commentsBefore   :: [(Int, LEpaComment)]
   , importStatement  :: LImportDecl GhcPs
   , commentsSameline :: [(Int, EpaCommentTok)]
-  , commentsAfter    :: [(Int, EpaCommentTok)]
+  , commentsAfter    :: [(Int, LEpaComment)]
   }
 
 instance Show ImportStatementRecord where
@@ -243,13 +266,13 @@ transformToImportLine startPos is =
       :: [LEpaComment] -> ExactPrint.Pos -> FinalList ImportLine ExactPrint.Pos
     flattenComms = \case
       [] -> finalPure
-      (L (Anchor span _) (EpaComment comm _) : commRest) -> \lastSpanEnd -> do
+      lcomm@(L (Anchor span _) _) : commRest -> \lastSpanEnd -> do
         case ExactPrint.ss2delta lastSpanEnd span of
           SameLine i -> do
-            finalYield $ SamelineComment (i, comm)
+            finalYield $ SamelineComment (i, lcomm)
           DifferentLine l c -> do
             finalYield $ EmptyLines (l - 1)
-            finalYield $ NewlineComment (c - 1, comm)
+            finalYield $ NewlineComment (c - 1, lcomm)
         flattenComms commRest (ExactPrint.ss2posEnd span)
     flattenDecls
       :: [LImportDecl GhcPs]
@@ -265,14 +288,12 @@ transformToImportLine startPos is =
                 EpAnn anch s (EpaCommentsBalanced cs1 cs2) ->
                   (reverse cs1, reverse cs2, EpAnn anch s (EpaComments []))
                 EpAnnNotUsed -> ([], [], EpAnnNotUsed)
-          in
+          in  do
-            do
                 span1 <- flattenComms commsBefore lastSpanEnd
                 let newlines = case ExactPrint.ss2delta span1 declSpan of
                       SameLine _        -> 0
                       DifferentLine i _ -> i - 1
-              finalYield
+                finalYield $ EmptyLines newlines
-                $ EmptyLines newlines
                 finalYield $ ImportStatement ImportStatementRecord
                   { commentsBefore   = []
                   , importStatement  = L (SrcSpanAnn cleanEpAnn srcSpan) decl
@@ -286,15 +307,15 @@ transformToImportLine startPos is =
   in
     flattenDecls is startPos
 
-data Partial = PartialCommsOnly [(Int, EpaCommentTok)]
+data Partial = PartialCommsOnly [(Int, LEpaComment)]
              | PartialImport ImportStatementRecord
 
 groupifyImportLines :: [ImportLine] -> [ImportLine]
 groupifyImportLines ls = finalToList_ $ go (PartialCommsOnly []) ls
  where
   go acc [] = case acc of
-    PartialCommsOnly comms ->
+    PartialCommsOnly comms -> reverse comms `forM_` \comm ->
-      reverse comms `forM_` \comm -> finalYield $ NewlineComment comm
+      finalYield $ NewlineComment comm
     PartialImport partialRecord ->
       finalYield $ ImportStatement $ unpartial partialRecord
   go acc (line1 : lineR) = do
@@ -307,8 +328,9 @@ groupifyImportLines ls = finalToList_ $ go (PartialCommsOnly []) ls
         SamelineComment comm -> do
           pure $ PartialCommsOnly (comm : comms)
         NewlineComment  comm   -> pure $ PartialCommsOnly (comm : comms)
-        ImportStatement record ->
+        ImportStatement record -> pure $ PartialImport $ record
-          pure $ PartialImport $ record { commentsBefore = comms }
+          { commentsBefore = comms
+          }
       PartialImport partialRecord -> case line1 of
         e@EmptyLines{} -> do
           finalYield $ ImportStatement $ unpartial partialRecord
@@ -317,7 +339,8 @@ groupifyImportLines ls = finalToList_ $ go (PartialCommsOnly []) ls
         SamelineComment comm -> do
           if (null $ commentsAfter partialRecord)
             then pure $ PartialImport partialRecord
-              { commentsSameline = comm : commentsSameline partialRecord
+              { commentsSameline = tokenOnly comm
+                                   : commentsSameline partialRecord
               }
             else pure $ PartialImport partialRecord
               { commentsAfter = comm : commentsAfter partialRecord
@@ -333,6 +356,8 @@ groupifyImportLines ls = finalToList_ $ go (PartialCommsOnly []) ls
           pure $ PartialImport $ record { commentsBefore = contestedComments }
             -- comments in between will stay connected to the following decl
     go newAcc lineR
+  tokenOnly :: (Int, LEpaComment) -> (Int, EpaCommentTok)
+  tokenOnly (ind, L _ (EpaComment tok _)) = (ind, tok)
   unpartial :: ImportStatementRecord -> ImportStatementRecord
   unpartial partialRecord = ImportStatementRecord
     { commentsBefore   = reverse (commentsBefore partialRecord)
@@ -361,8 +386,8 @@ sortCommentedImports =
     Left  x -> [x]
     Right y -> ImportStatement <$> y
   sortGroups :: [ImportStatementRecord] -> [ImportStatementRecord]
-  sortGroups =
+  sortGroups = List.sortOn
-    List.sortOn (moduleNameString . unLoc . ideclName . unLoc . importStatement)
+    (moduleNameString . unLoc . ideclName . unLoc . importStatement)
   groupify :: [ImportLine] -> [Either ImportLine [ImportStatementRecord]]
   groupify cs = go [] cs
    where

source/library/Language/Haskell/Brittany/Internal/S3_ToBriDocTools.hs

@@ -389,6 +389,9 @@ docSeq :: [ToBriDocM BriDocNumbered] -> ToBriDocM BriDocNumbered
 docSeq [] = docEmpty
 docSeq l = allocateNode . BDSeq =<< sequence l
 
+docSeqSep :: [ToBriDocM BriDocNumbered] -> ToBriDocM BriDocNumbered
+docSeqSep = docSeq . List.intersperse docSeparator
+
 docLines :: [ToBriDocM BriDocNumbered] -> ToBriDocM BriDocNumbered
 docLines l = allocateNode . BDLines =<< sequence l
 
@@ -720,6 +723,10 @@ instance DocFlushCommsPost (Maybe GHC.RealSrcSpan) (ToBriDocM BriDocNumbered) wh
       bd <- bdm
       pure (i1, BDFlushCommentsPost (GHC.realSrcSpanEnd loc) shouldMark bd)
 
+instance DocFlushCommsPost GHC.EpaLocation (ToBriDocM BriDocNumbered) where
+  docFlushCommsPost shouldMark epaLocation =
+    docFlushCommsPost shouldMark (Just $ GHC.epaLocationRealSrcSpan epaLocation)
+
 instance DocFlushCommsPost ann (ToBriDocM BriDocNumbered)
       => DocFlushCommsPost ann (ToBriDocM [BriDocNumbered]) where
   docFlushCommsPost shouldMark loc bdm = do

source/library/Language/Haskell/Brittany/Internal/S4_WriteBriDoc.hs

@@ -275,21 +275,53 @@ layoutBriDocM = \case
     layoutBriDocM bd
   BDFlushCommentsPrior loc bd -> do
     comms <- takeBefore loc
+    startCurY <- mGet <&> _lstate_curY
     printComments comms
     mModify (\s -> s + CommentCounter (length comms))
     mModify $ \s -> s
       { _lstate_markerForDelta = Nothing
-      , _lstate_plannedSpace = case _lstate_markerForDelta s of
+      , _lstate_plannedSpace =
+        case _lstate_markerForDelta s of
           Nothing -> _lstate_plannedSpace s
           Just m ->
             let p1 = (srcLocLine m, srcLocCol m)
                 p2 = (srcLocLine loc, srcLocCol loc)
-            -- traceShow (m, ExactPrint.pos2delta p1 p2) $ pure ()
+            in -- trace ("_lstate_plannedSpace = " ++ show (_lstate_plannedSpace s)
-            in case ExactPrint.pos2delta p1 p2 of
+               --   ++ ", _lstate_markerForDelta = " ++ show (_lstate_markerForDelta s)
-              SameLine{} -> _lstate_plannedSpace s
+               --   ++ ", _lstate_curY = " ++ show (_lstate_curY s)
+               --   ++ ", p1 = " ++ show p1
+               --   ++ ", p2 = " ++ show p2
+               --   ++ ", startCurY = " ++ show startCurY
+               --   -- ++ ", delta = " ++ show (ExactPrint.pos2delta p1 p2)
+               -- ) $
+              case ExactPrint.pos2delta p1 p2 of
+              SameLine iDelta -> case _lstate_plannedSpace s of
+                -- There is a delta after a marker. That should only happen
+                -- after a block-comment. And the marker-delta is SameLine,
+                -- so if layout doesn't force a newline we respect the marker
+                -- delta (i.e. respect whitespace immediately after a block
+                -- comment) or we just use the plan.
+                PlannedNone        -> PlannedSameline iDelta
+                PlannedSameline i  -> PlannedSameline (max (iDelta - 0) i)
+                p@PlannedNewline{} -> p
+                p@PlannedDelta{}   -> p
               DifferentLine n _ -> case _lstate_plannedSpace s of
-                PlannedNone       -> PlannedNone
+                -- Marker with DifferentLine delta means that we want to
-                PlannedSameline i -> PlannedDelta n (_lstate_curY s + i)
+                -- reproduce the newlines that were present in the input.
+                -- These will be emptylines in cases where it makes sense to
+                -- reproduce them, e.g. between statements in a do-block.
+                PlannedNone       -> PlannedDelta n startCurY
+                                     --             ^^^^^^^^^
+                                     --
+                                     -- after a block-comment, _lstate_curY
+                                     -- matches the end of the comment.
+                                     -- But to not break layout we need to
+                                     -- restore the original.
+                                     -- E.g. consider > let {-comm-}
+                                     --               >     x = 13
+                                     --
+                                     --             vvvvvvvvvvvvvvv
+                PlannedSameline i -> PlannedDelta n (startCurY + i)
                 PlannedNewline{}  -> PlannedNewline n
                 PlannedDelta _ i  -> PlannedDelta n i
       }

source/library/Language/Haskell/Brittany/Internal/StepOrchestrate.hs

@@ -1,9 +1,9 @@
 {-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE DataKinds #-}
 
 module Language.Haskell.Brittany.Internal.StepOrchestrate
   ( processModule
-  )
+  ) where
-where
 
 import           Language.Haskell.Brittany.Internal.Prelude
 
@@ -15,7 +15,8 @@ import qualified Data.Text.Lazy                as TextL
 import qualified Data.Text.Lazy.Builder        as TextL.Builder
 import qualified Data.Text.Lazy.Builder        as Text.Builder
 import qualified GHC
-import           GHC                            ( EpaCommentTok
+import           GHC                            ( EpaComment(EpaComment)
+                                                , EpaCommentTok
                                                   ( EpaBlockComment
                                                   , EpaEofComment
                                                   , EpaLineComment
@@ -36,7 +37,7 @@ import           Language.Haskell.Brittany.Internal.Config.Types
 import           Language.Haskell.Brittany.Internal.Config.Types.Instances2
                                                 ( )
 import           Language.Haskell.Brittany.Internal.S2_SplitModule
-                                                ( splitModule )
+                                                ( splitModuleStart )
 import           Language.Haskell.Brittany.Internal.S3_ToBriDocTools
 import           Language.Haskell.Brittany.Internal.S4_WriteBriDoc
                                                 ( ppBriDoc )
@@ -46,7 +47,8 @@ import           Language.Haskell.Brittany.Internal.ToBriDoc.Module
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.Util.AST
 import           Language.Haskell.Brittany.Internal.Utils
-import           Language.Haskell.Brittany.Internal.ToBriDoc (layouters)
+import           Language.Haskell.Brittany.Internal.ToBriDoc
+                                                ( layouters )
 
 
 
@@ -58,18 +60,10 @@ processModule
   :: TraceFunc
   -> Config
   -> PerItemConfig
-  -> GHC.ParsedSource
+  -> FinalList ModuleElement p
   -> IO ([BrittanyError], TextL.Text)
-processModule traceFunc conf inlineConf parsedModule = do
+processModule traceFunc conf inlineConf moduleElems = do
-  let shouldReformatHead =
+  let FinalList moduleElementsStream = moduleElems
-        conf & _conf_layout & _lconfig_reformatModulePreamble & confUnpack
-  let
-    wrapNonDeclToBriDoc = MultiRWSS.withMultiReader conf
-      . MultiRWSS.withMultiState_ (CommentCounter 0)
-    FinalList moduleElementsStream = splitModule
-      shouldReformatHead
-      parsedModule
-      (fmap GHC.realSrcSpanStart $ obtainAnnPos (GHC.hsmodAnn $ GHC.unLoc parsedModule) GHC.AnnWhere)
       ((out, errs), debugStrings) =
         runIdentity
           $ MultiRWSS.runMultiRWSTNil
@@ -79,59 +73,7 @@ processModule traceFunc conf inlineConf parsedModule = do
           $ MultiRWSS.withMultiReader traceFunc
           $ moduleElementsStream
               (\modElem cont -> do
-              case modElem of
+                processModuleElement modElem
-                MEExactModuleHead modHead -> wrapNonDeclToBriDoc $ do
-                  bdMay <- ppModuleHead modHead
-                  case bdMay of
-                    Nothing -> pure ()
-                    Just bd -> ppBriDoc bd True
-                MEPrettyModuleHead (L loc modHead) -> wrapNonDeclToBriDoc $ do
-                  case modHead of
-                    HsModule epAnn _layoutInfo Nothing Nothing _ _ _ _ -> do
-                      (bd, _) <-
-                        briDocMToPPM layouters
-                        $ maybe id
-                                docFlushRemaining
-                                (srcSpanFileName_maybe loc)
-                        $ docHandleComms epAnn docSeparator
-                      ppBriDoc bd True
-                    HsModule _ _layoutInfo Nothing Just{} _ _ _ _ -> error
-                      "brittany internal error: exports without module name"
-                    HsModule epAnn _layoutInfo (Just n) les _ _ _ _ -> do
-                      (bd, _) <-
-                        briDocMToPPM layouters
-                        $ maybe id
-                                docFlushRemaining
-                                (srcSpanFileName_maybe loc)
-                        $ moduleNameExportBridoc epAnn n les
-                      ppBriDoc bd True
-                MEImportDecl importDecl immediateAfterComms ->
-                  wrapNonDeclToBriDoc $ do
-                    (bd, _) <-
-                      briDocMToPPM layouters
-                        $ docSeq
-                            ( layoutImport importDecl
-                            : map commentToDoc immediateAfterComms
-                            )
-                    ppBriDoc bd False
-                MEDecl decl immediateAfterComms -> do
-                  let declConfig = getDeclConfig conf inlineConf decl
-                  MultiRWSS.withMultiReader declConfig
-                    $ MultiRWSS.withMultiState_ (CommentCounter 0)
-                    $ ppToplevelDecl decl immediateAfterComms
-                MEComment (ind, EpaLineComment str) -> do
-                  mTell $ TextL.Builder.fromString (replicate ind ' ' ++ str)
-                  mTell $ TextL.Builder.fromString "\n"
-                MEComment (ind, EpaBlockComment str) -> do
-                  mTell $ TextL.Builder.fromString (replicate ind ' ' ++ str)
-                  mTell $ TextL.Builder.fromString "\n"
-                MEComment (_, EpaEofComment) -> pure ()
-                MEComment _ ->
-                  mTell $ TextL.Builder.fromString "some other comment"
-                MEWhitespace dp -> do
-                  -- mTell $ TextL.Builder.fromString "B"
-                  -- mTell $ TextL.Builder.fromString ("whitespace " ++ show dp)
-                  ppmMoveToExactLoc dp
                 cont
               )
               (\x -> do
@@ -151,13 +93,94 @@ processModule traceFunc conf inlineConf parsedModule = do
   --       MEExactModuleHead{}  -> useTraceFunc traceFunc "MEExactModuleHead"
   --       MEPrettyModuleHead{} -> useTraceFunc traceFunc "MEPrettyModuleHead"
   --       MEImportDecl{}       -> useTraceFunc traceFunc "MEImportDecl"
-  --       MEDecl{}             -> useTraceFunc traceFunc "MEDecl"
+  --       MEDecl decl _ ->
-  --       MEComment{}          -> useTraceFunc traceFunc "MEComment"
+  --         useTraceFunc
+  --           traceFunc
+  --           ("MEDecl " ++ intercalate "," (getDeclBindingNames decl))
+  --       MEComment (y, L _ (EpaComment (EpaLineComment str) _)) ->
+  --         useTraceFunc traceFunc ("MEComment " ++ show y ++ " " ++ str)
+  --       MEComment (y, L _ (EpaComment (EpaBlockComment str) _)) ->
+  --         useTraceFunc traceFunc ("MEComment " ++ show y ++ " " ++ take 5 str)
+  --       MEComment (y, _) ->
+  --         useTraceFunc traceFunc ("MEComment " ++ show y ++ " _")
   --       MEWhitespace dp -> useTraceFunc traceFunc ("MEWhitespace " ++ show dp)
   --     rest
   --   )
   --   (\_ -> pure ())
   pure (errs, TextL.Builder.toLazyText out)
+ where
+  shouldReformatHead =
+    conf & _conf_layout & _lconfig_reformatModulePreamble & confUnpack
+  wrapNonDeclToBriDoc =
+    MultiRWSS.withMultiReader conf . MultiRWSS.withMultiState_
+      (CommentCounter 0)
+  processModuleElement
+    :: ModuleElement
+    -> MultiRWSS.MultiRWST
+         '[TraceFunc]
+         '[Text.Builder.Builder , [BrittanyError] , Seq String]
+         '[]
+         Identity
+         ()
+  processModuleElement = \case
+    MEExactModuleHead modHead -> if shouldReformatHead
+      then do
+        let FinalList startElems =
+              splitModuleStart
+                modHead
+                ( fmap GHC.realSrcSpanStart
+                $ obtainAnnPos (GHC.hsmodAnn $ GHC.unLoc modHead) GHC.AnnWhere
+                )
+        startElems
+          (\modElem cont -> do
+            processModuleElement modElem
+            cont
+          )
+          (\_ -> pure ())
+      else wrapNonDeclToBriDoc $ do
+        bdMay <- ppModuleHead modHead
+        case bdMay of
+          Nothing -> pure ()
+          Just bd -> do
+            ppBriDoc bd True
+        mTell $ Text.Builder.fromString "\n"
+    MEPrettyModuleHead (L loc modHead) -> wrapNonDeclToBriDoc $ do
+      case modHead of
+        HsModule epAnn _layoutInfo Nothing Nothing _ _ _ _ -> do
+          (bd, _) <-
+            briDocMToPPM layouters
+            $ maybe id docFlushRemaining (srcSpanFileName_maybe loc)
+            $ docHandleComms epAnn docSeparator
+          ppBriDoc bd True
+        HsModule _ _layoutInfo Nothing Just{} _ _ _ _ ->
+          error "brittany internal error: exports without module name"
+        HsModule epAnn _layoutInfo (Just n) les _ _ _ _ -> do
+          (bd, _) <-
+            briDocMToPPM layouters
+            $ maybe id docFlushRemaining (srcSpanFileName_maybe loc)
+            $ moduleNameExportBridoc epAnn n les
+          ppBriDoc bd True
+    MEImportDecl importDecl immediateAfterComms -> wrapNonDeclToBriDoc $ do
+      (bd, _) <- briDocMToPPM layouters $ docSeq
+        (layoutImport importDecl : map commentToDoc immediateAfterComms)
+      ppBriDoc bd False
+    MEDecl decl immediateAfterComms -> do
+      let declConfig = getDeclConfig conf inlineConf decl
+      MultiRWSS.withMultiReader declConfig
+        $ MultiRWSS.withMultiState_ (CommentCounter 0)
+        $ ppToplevelDecl decl immediateAfterComms
+    MEComment (ind, L _ (EpaComment (EpaLineComment str) _)) -> do
+      mTell $ TextL.Builder.fromString (replicate ind ' ' ++ str)
+      mTell $ TextL.Builder.fromString "\n"
+    MEComment (ind, L _ (EpaComment (EpaBlockComment str) _)) -> do
+      mTell $ TextL.Builder.fromString (replicate ind ' ' ++ str)
+      mTell $ TextL.Builder.fromString "\n"
+    MEComment (_, L _ (EpaComment EpaEofComment _)) -> pure ()
+    MEComment    _  -> mTell $ TextL.Builder.fromString "some other comment"
+    MEWhitespace dp -> do
+      -- mTell $ TextL.Builder.fromString "B"
+      -- mTell $ TextL.Builder.fromString ("whitespace " ++ show dp)
+      ppmMoveToExactLoc dp
 
 commentToDoc :: (Int, EpaCommentTok) -> ToBriDocM BriDocNumbered
 commentToDoc (indent, c) = case c of
@@ -197,17 +220,13 @@ processDefault x = do
     _    -> mTell $ Text.Builder.fromString $ List.dropWhileEnd ((==) '\n') str
 
 
-getDeclConfig
+getDeclConfig :: Config -> PerItemConfig -> GHC.LHsDecl GhcPs -> Config
-  :: Config
-  -> PerItemConfig
-  -> GHC.LHsDecl GhcPs
-  -> Config
 getDeclConfig config inlineConf decl = cZipWith fromOptionIdentity config
   $ mconcat (catMaybes (mBindingConfs ++ [mDeclConf]))
  where
   declBindingNames = getDeclBindingNames decl
-  mBindingConfs =
+  mBindingConfs    = declBindingNames <&> \n ->
-    declBindingNames <&> \n -> Map.lookup n $ _icd_perBinding inlineConf
+    Map.lookup n $ _icd_perBinding inlineConf
   mDeclConf = case GHC.locA $ GHC.getLoc decl of
     GHC.RealSrcSpan x _ -> Map.lookup x $ _icd_perAnchor inlineConf
     GHC.UnhelpfulSpan{} -> Nothing
@@ -217,16 +236,15 @@ ppToplevelDecl decl immediateAfterComms = do
   exactprintOnly <- mAsk <&> \declConfig ->
     declConfig & _conf_roundtrip_exactprint_only & confUnpack
   bd <- fmap fst $ if exactprintOnly
-    then briDocMToPPM layouters
+    then briDocMToPPM layouters $ docSeq
-      $ docSeq
       (briDocByExactNoComment decl : map commentToDoc immediateAfterComms)
     else do
       let innerDoc = case decl of
             L (SrcSpanAnn _ (GHC.RealSrcSpan s _)) _ ->
               docFlushRemaining (GHC.srcSpanFile s) $ layoutDecl decl
             _ -> layoutDecl decl
-      (r, errorCount) <- briDocMToPPM layouters
+      (r, errorCount) <- briDocMToPPM layouters $ docSeq
-        $ docSeq (innerDoc : map commentToDoc immediateAfterComms)
+        (innerDoc : map commentToDoc immediateAfterComms)
       if errorCount == 0
         then pure (r, 0)
         else briDocMToPPM layouters $ briDocByExactNoComment decl

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/DataDecl.hs

@@ -15,7 +15,7 @@ import Language.Haskell.Brittany.Internal.Components.BriDoc
 
 
 layoutDataDecl
-  :: LTyClDecl GhcPs
+  :: Maybe (LTyClDecl GhcPs)
   -> EpAnn [AddEpAnn]
   -> LIdP GhcPs
   -> LHsQTyVars GhcPs
@@ -35,7 +35,7 @@ layoutDataDecl ltycl declEpAnn name (HsQTvs _ bndrs) pats defn = case defn of
           then do
             nameStr <- lrdrNameToTextAnn name
             consNameStr <- lrdrNameToTextAnn consName
-            tyVarLine <- shareDoc $ createBndrDoc bndrs
+            tyVars <- mapM shareDoc $ createBndrDoc bndrs
             patDocs <- mapM shareDoc $ layoutHsTyPats pats
             -- headDoc     <- fmap return $ docSeq
             --   [ appSep $ docLitS "newtype")
@@ -43,29 +43,111 @@ layoutDataDecl ltycl declEpAnn name (HsQTvs _ bndrs) pats defn = case defn of
             --   , appSep tyVarLine
             --   ]
             rhsDoc <- return <$> createDetailsDoc consNameStr details
-            docHandleComms declEpAnn $ createDerivingPar mDerivs $ docSeq
+            docHandleComms declEpAnn $ createDerivingPar mDerivs $ docAlt
+              [ -- newtype Tagged s b = Tagged { unTagged :: b }
+                docSeq
                 [ appSep $ docLitS "newtype"
                 , appSep $ docLit nameStr
-              , appSep tyVarLine
+                , appSep (docSeqSep tyVars)
                 , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
                 , docSeparator
                 , docLitS "="
                 , docSeparator
+                , docForceParSpacing $ docHandleComms epAnn $ rhsDoc
+                ]
+              , -- newtype Tagged s b
+                --   = Tagged { unTagged :: b }
+                -- newtype Tagged s
+                --                b
+                --   = Tagged { unTagged :: b }
+                docAddBaseY BrIndentRegular $ docPar
+                  ( docSeq
+                    [ appSep $ docLitS "newtype"
+                    , appSep $ docLit nameStr
+                    , docAlt
+                      [ docForceSingleline $ docSeq
+                        [ appSep (docSeqSep tyVars)
+                        , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
+                        ]
+                      , docSetBaseY $ docLines
+                        $ map docForceSingleline $ tyVars ++ patDocs
+                      ]
+                    ]
+                  )
+                  ( docSeq
+                    [ docLitS "="
+                    , docSeparator
                     , docHandleComms epAnn $ rhsDoc
                     ]
-          else briDocByExactNoComment ltycl
+                  )
-      _ -> briDocByExactNoComment ltycl
+              , -- newtype Tagged
+                --   s
+                --   b
+                --   = Tagged { unTagged :: b }
+                docAddBaseY BrIndentRegular $ docPar
+                  ( docSeq
+                    [ appSep $ docLitS "newtype"
+                    , appSep $ docLit nameStr
+                    -- , appSep tyVarLine
+                    -- , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
+                    ]
+                  )
+                  ( docLines
+                    $  map (docEnsureIndent BrIndentRegular) tyVars
+                    ++ map (docEnsureIndent BrIndentRegular) patDocs
+                    ++ [ docSeq
+                         [ docLitS "="
+                         , docSeparator
+                         , docHandleComms epAnn $ rhsDoc
+                         ]
+                       ]
+                  )
+              ]
+          else maybe
+            (error
+            $  "Unsupported form of DataFamInstDecl:"
+            ++ " ConDeclH98 with context"
+            )
+            briDocByExactNoComment
+            ltycl
+      _ -> maybe
+            (error
+            $  "Unsupported form of DataFamInstDecl:"
+            ++ " ConDeclH98 with forall"
+            )
+            briDocByExactNoComment
+            ltycl
+  HsDataDefn NoExtField NewType _ _ Just{} _ _ -> maybe
+    (error $ "Unsupported form of DataFamInstDecl: NewType _ _ Just _ _")
+    briDocByExactNoComment
+    ltycl
+  HsDataDefn NoExtField NewType _ _ Nothing _ _ -> maybe
+    (error $ "Unsupported form of DataFamInstDecl: NewType _ _ Nothing _ _")
+    briDocByExactNoComment
+    ltycl
 
-
+  -- data MyData = MyData ..
-  -- data MyData a b
+  -- data MyData = MyData { .. }
-  -- (zero constructors)
+  HsDataDefn NoExtField DataType ctxMay _ctype Nothing conss mDerivs -> do
-  HsDataDefn NoExtField DataType ctxMay _ctype Nothing [] mDerivs -> do
     lhsContextDoc <- case ctxMay of
       Just (L _ lhsContext) -> shareDoc $ createContextDoc lhsContext
       Nothing -> pure docEmpty
     nameStr <- lrdrNameToTextAnn name
-    tyVarLine <- return <$> createBndrDoc bndrs
+    tyVarLine <- shareDoc $ docSeqSep $ createBndrDoc bndrs
     patDocs <- mapM shareDoc $ layoutHsTyPats pats
+    lhsDoc <- shareDoc $ docSeq
+      [ -- TOOD92 docNodeAnnKW ltycl (Just GHC.AnnData) $ 
+        appSep $ docLitS "data"
+      , docForceSingleline $ lhsContextDoc
+      , appSep $ docLit nameStr
+      , appSep tyVarLine
+      , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
+      ]
+    let prefixes = "=" : repeat "|"
+    layoutConssResult <- mapM layoutConDecl (zip prefixes conss)
+    case sequence layoutConssResult of
+      Left err -> maybe (error err) briDocByExactNoComment ltycl
+      Right [] -> do
         docHandleComms declEpAnn $ createDerivingPar mDerivs $ docSeq
           [ appSep $ docLitS "data"
           , lhsContextDoc
@@ -73,151 +155,140 @@ layoutDataDecl ltycl declEpAnn name (HsQTvs _ bndrs) pats defn = case defn of
           , appSep tyVarLine
           , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
           ]
-
+      Right [(consDocSl, consDocMl)] -> do
-  -- data MyData = MyData ..
-  -- data MyData = MyData { .. }
-  HsDataDefn NoExtField DataType ctxMay _ctype Nothing [cons] mDerivs ->
-    case cons of
-      (L _ (ConDeclH98 epAnn consName _hasExt qvars mRhsContext details _conDoc))
-        -> do
-          lhsContextDoc <- case ctxMay of
-            Just (L _ lhsContext) -> shareDoc $ createContextDoc lhsContext
-            Nothing -> pure docEmpty
-          nameStr <- lrdrNameToTextAnn name
-          consNameStr <- lrdrNameToTextAnn consName
-          tyVarLine <- return <$> createBndrDoc bndrs
-          patDocs <- mapM shareDoc $ layoutHsTyPats pats
-          forallDocMay <- case createForallDoc qvars of
-            Nothing -> pure Nothing
-            Just x -> Just . pure <$> x
-          rhsContextDocMay <- case mRhsContext of
-            Nothing -> pure Nothing
-            Just (L _ ctxt) -> Just . pure <$> createContextDoc ctxt
-          rhsDoc <- return <$> createDetailsDoc consNameStr details
-          let posEqual = obtainAnnPos epAnn AnnEqual
-          consDoc <-
-            shareDoc
-            $ docHandleComms epAnn
-            $ docHandleComms posEqual
-            $ docNonBottomSpacing
-            $ case (forallDocMay, rhsContextDocMay) of
-                (Just forallDoc, Just rhsContextDoc) -> docLines
-                  [ docSeq
-                    [docLitS "=", docSeparator, docForceSingleline forallDoc]
-                  , docSeq
-                    [ docLitS "."
-                    , docSeparator
-                    , docSetBaseY $ docLines [rhsContextDoc, docSetBaseY rhsDoc]
-                    ]
-                  ]
-                (Just forallDoc, Nothing) -> docLines
-                  [ docSeq
-                    [docLitS "=", docSeparator, docForceSingleline forallDoc]
-                  , docSeq [docLitS ".", docSeparator, rhsDoc]
-                  ]
-                (Nothing, Just rhsContextDoc) -> docSeq
-                  [ docLitS "="
-                  , docSeparator
-                  , docSetBaseY $ docLines [rhsContextDoc, docSetBaseY rhsDoc]
-                  ]
-                (Nothing, Nothing) ->
-                  docSeq [docLitS "=", docSeparator, rhsDoc]
         docHandleComms declEpAnn $ createDerivingPar mDerivs $ docAlt
           [ -- data D = forall a . Show a => D a
-              docSeq
+            docSeq [lhsDoc, consDocSl]
-              [ -- TOOD92 docNodeAnnKW ltycl (Just GHC.AnnData) $ 
-                docSeq
-                [ appSep $ docLitS "data"
-                , docForceSingleline $ lhsContextDoc
-                , appSep $ docLit nameStr
-                , appSep tyVarLine
-                , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
-                ]
-              , docHandleComms epAnn $ docHandleComms posEqual $ docLitS "="
-              , docSeparator
-              , docSetIndentLevel $ docSeq
-                [ case forallDocMay of
-                  Nothing -> docEmpty
-                  Just forallDoc ->
-                    docSeq
-                      [ docForceSingleline forallDoc
-                      , docSeparator
-                      , docLitS "."
-                      , docSeparator
-                      ]
-                , maybe docEmpty docForceSingleline rhsContextDocMay
-                , rhsDoc
-                ]
-              ]
           , -- data D
             --   = forall a . Show a => D a
-              docAddBaseY BrIndentRegular $ docPar
+            -- data D
-              ( -- TODO92 docNodeAnnKW ltycl (Just GHC.AnnData) $ 
-                docSeq
-                [ appSep $ docLitS "data"
-                , docForceSingleline lhsContextDoc
-                , appSep $ docLit nameStr
-                , tyVarLine
-                , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
-                ]
-              )
-              (docSeq
-                [ docHandleComms epAnn $ docHandleComms posEqual $ docLitS "="
-                , docSeparator
-                , docSetIndentLevel $ docSeq
-                  [ case forallDocMay of
-                    Nothing -> docEmpty
-                    Just forallDoc ->
-                      docSeq
-                        [ docForceSingleline forallDoc
-                        , docSeparator
-                        , docLitS "."
-                        , docSeparator
-                        ]
-                  , maybe docEmpty docForceSingleline rhsContextDocMay
-                  , rhsDoc
-                  ]
-                ]
-              )
-            , -- data D
             --   = forall a
             --   . Show a =>
             --     D a
-              docAddBaseY BrIndentRegular $ docPar
+            docAddBaseY BrIndentRegular
-              ( -- TODO92 docNodeAnnKW ltycl (Just GHC.AnnData) $ 
+            $ docPar lhsDoc
-                docSeq
+              (docNonBottomSpacing $ docAlt [consDocSl, consDocMl])
-                [ appSep $ docLitS "data"
-                , docForceSingleline lhsContextDoc
-                , appSep $ docLit nameStr
-                , tyVarLine
-                , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
-                ]
-              )
-              consDoc
           , -- data
             --   Show a =>
             --   D
-              --   = forall a
+            --   = rhsDoc
-              --   . Show a =>
-              --     D a
             -- This alternative is only for -XDatatypeContexts.
             -- But I think it is rather unlikely this will trigger without
             -- -XDataTypeContexts, especially with the `docNonBottomSpacing`
             -- above, so while not strictly necessary, this should not
             -- hurt.
             docAddBaseY BrIndentRegular $ docPar
-              (docLitS "data")
+            (-- TODO92 docNodeAnnKW ltycl (Just GHC.AnnData) $
+             docLitS "data")
             (docLines
               [ lhsContextDoc
-                , -- TODO92 docNodeAnnKW ltycl (Just GHC.AnnData) $
+              , docSeq
-                  docSeq [appSep $ docLit nameStr, tyVarLine, docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]]
+                [ appSep $ docLit nameStr
-                , consDoc
+                , tyVarLine
+                , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
+                ]
+              , consDocMl
               ]
             )
           ]
-      _ -> briDocByExactNoComment ltycl
+      Right consDocTuples -> do
+        docHandleComms declEpAnn
+          $ createDerivingPar mDerivs
+          $ docAddBaseY BrIndentRegular
+          $ docPar
+            (docAlt
+              [ -- data Show a => D a
+                lhsDoc
+              , -- data
+                --   Show a =>
+                --   D
+                -- This alternative is only for -XDatatypeContexts.
+                -- But I think it is rather unlikely this will trigger without
+                -- -XDataTypeContexts, especially with the `docNonBottomSpacing`
+                -- above, so while not strictly necessary, this should not
+                -- hurt.
+                docAddBaseY BrIndentRegular $ docPar
+                (-- TODO92 docNodeAnnKW ltycl (Just GHC.AnnData) $
+                 docLitS "data")
+                (docLines
+                  [ lhsContextDoc
+                  , docSeq
+                    [ appSep $ docLit nameStr
+                    , tyVarLine
+                    , docSeq $ [x | p <- patDocs, x <- [p, docSeparator]]
+                    ]
+                  ]
+                )
+              ]
+            )
+            (docLines $ [docAlt [sl, ml] | (sl, ml) <- consDocTuples])
+  
+  HsDataDefn NoExtField DataType _ _ Just{} _ _ -> maybe
+    (error $ "Unsupported form of DataFamInstDecl: DataType _ _ Just _ _")
+    briDocByExactNoComment
+    ltycl
+
+layoutConDecl
+  :: (String, LConDecl GhcPs)
+  -> ToBriDocM
+       (Either String (ToBriDocM BriDocNumbered, ToBriDocM BriDocNumbered))
+layoutConDecl (prefix, L _ con) = case con of
+  ConDeclH98 epAnn consName _hasExt qvars mRhsContext details _conDoc -> do
+    consNameStr  <- lrdrNameToTextAnn consName
+    forallDocMay <- case createForallDoc qvars of
+      Nothing -> pure Nothing
+      Just x  -> Just . pure <$> x
+    rhsContextDocMay <- case mRhsContext of
+      Nothing         -> pure Nothing
+      Just (L _ ctxt) -> Just . pure <$> createContextDoc ctxt
+    detailsDoc <- shareDoc $ createDetailsDoc consNameStr details
+    let posEqual = obtainAnnPos epAnn AnnEqual
+    pure $ Right
+      ( docSeq
+          [ docHandleComms epAnn $ docHandleComms posEqual $ docLitS prefix
+          , docSeparator
+          , docSetIndentLevel $ docSeq
+            [ case forallDocMay of
+              Nothing        -> docEmpty
+              Just forallDoc -> docSeq
+                [ docForceSingleline forallDoc
+                , docSeparator
+                , docLitS "."
+                , docSeparator
+                ]
+            , maybe docEmpty docForceSingleline rhsContextDocMay
+            , detailsDoc
+            ]
+          ]
+      , docHandleComms epAnn
+        $ docHandleComms posEqual
+        $ docNonBottomSpacing
+        $ case (forallDocMay, rhsContextDocMay) of
+            (Just forallDoc, Just rhsContextDoc) -> docLines
+              [ docSeq
+                [docLitS prefix, docSeparator, docForceSingleline forallDoc]
+              , docSeq
+                [ docLitS "."
+                , docSeparator
+                , docSetBaseY $ docLines [rhsContextDoc, docSetBaseY detailsDoc]
+                ]
+              ]
+            (Just forallDoc, Nothing) -> docLines
+              [ docSeq
+                [docLitS prefix, docSeparator, docForceSingleline forallDoc]
+              , docSeq [docLitS ".", docSeparator, detailsDoc]
+              ]
+            (Nothing, Just rhsContextDoc) -> docSeq
+              [ docLitS prefix
+              , docSeparator
+              , docSetBaseY $ docLines [rhsContextDoc, docSetBaseY detailsDoc]
+              ]
+            (Nothing, Nothing) -> docSeq
+              [docLitS prefix, docSeparator, detailsDoc]
+      )
+  ConDeclGADT{} -> pure
+    $ Left "Unsupported: ConDeclGADT inside DataFamInstDecl"
 
-  _ -> briDocByExactNoComment ltycl
 
 layoutHsTyPats
   :: [LHsTypeArg GhcPs] -> [ToBriDocM BriDocNumbered]
@@ -253,14 +324,13 @@ createContextDoc (t1 : tR) = do
       ]
     ]
 
-createBndrDoc :: [LHsTyVarBndr flag GhcPs] -> ToBriDocM BriDocNumbered
+createBndrDoc :: [LHsTyVarBndr flag GhcPs] -> [ToBriDocM BriDocNumbered]
-createBndrDoc bs = do
+createBndrDoc = map $ \x -> do
-  tyVarDocs <- bs `forM` \case
+  (vname, mKind) <- case x of
     (L _ (UserTyVar _ _ext vname)) -> return $ (lrdrNameToText vname, Nothing)
     (L _ (KindedTyVar _ _ext lrdrName kind)) -> do
       d <- shareDoc $ callLayouter layout_type kind
       return $ (lrdrNameToText lrdrName, Just $ d)
-  docSeq $ List.intersperse docSeparator $ tyVarDocs <&> \(vname, mKind) ->
   case mKind of
     Nothing -> docLit vname
     Just kind -> docSeq
@@ -385,8 +455,7 @@ createDetailsDoc consNameStr details = case details of
     let ((fName1, fType1), fDocR) = case mkFieldDocs fields of
           (doc1:docR) -> (doc1, docR)
           _ -> error "cannot happen (TM)"
-    -- allowSingleline <- mAsk <&> _conf_layout .> _lconfig_allowSinglelineRecord .> confUnpack
+    allowSingleline <- mAsk <&> _conf_layout .> _lconfig_allowSinglelineRecord .> confUnpack
-    let allowSingleline = False
     docAddBaseY BrIndentRegular $ runFilteredAlternative $ do
         -- single-line: { i :: Int, b :: Bool }
       addAlternativeCond allowSingleline $ docSeq
@@ -412,7 +481,7 @@ createDetailsDoc consNameStr details = case details of
         , docSeparator
         , docHandleComms posClose $ docLitS "}"
         ]
-      addAlternative $ docPar
+      addAlternative $ docSetParSpacing $ docPar
         (docLit consNameStr)
         (docNonBottomSpacingS $ docLines
           [ docAlt
@@ -468,7 +537,7 @@ createForallDoc
   :: [LHsTyVarBndr flag GhcPs] -> Maybe (ToBriDocM BriDocNumbered)
 createForallDoc [] = Nothing
 createForallDoc lhsTyVarBndrs =
-  Just $ docSeq [docLitS "forall ", createBndrDoc lhsTyVarBndrs]
+  Just $ docSeq [docLitS "forall ", docSeqSep $ createBndrDoc lhsTyVarBndrs]
 
 createNamesAndTypeDoc
   :: LConDeclField GhcPs

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/Decl.hs

@@ -238,7 +238,10 @@ layoutGrhs (L _ (GRHS epAnn guards body)) = do
   guardDocs <- case guards of
     [] -> pure []
     _  -> docFlushCommsPost False posArrow $ callLayouter layout_stmt `mapM` guards
-  bodyDoc <- callLayouter layout_expr body
+  let bodyEndPos = case locA $ getLoc body of
+        GHC.RealSrcSpan s _ -> Just s
+        GHC.UnhelpfulSpan{} -> Nothing
+  bodyDoc <- docFlushCommsPost True bodyEndPos $ callLayouter layout_expr body
   return (Just epAnn, guardDocs, bodyDoc)
 
 layoutPatternBind
@@ -260,7 +263,7 @@ layoutPatternBind funId binderDoc lmatch@(L _ match) = do
       let t' = fixPatternBindIdentifier match t
       docLit t'
     _ -> pure Nothing
-  patDoc <- docHandleComms lmatch $ case (mIdDoc, patDocs) of -- TODO92 we use lmatch twice here!
+  patDoc <- case (mIdDoc, patDocs) of
     (Just idDoc, p1 : p2 : pr) | isInfix -> if null pr
       then docCols
         ColPatternsFuncInfix
@@ -805,7 +808,7 @@ layoutTyCl ltycl@(L _loc tycl) = case tycl of
                        typeDoc
   DataDecl epAnn name tyVars _ dataDefn -> do
     layouters <- mAsk
-    layout_dataDecl layouters ltycl epAnn name tyVars [] dataDefn
+    layout_dataDecl layouters (Just ltycl) epAnn name tyVars [] dataDefn
   _ -> briDocByExactNoComment ltycl
 
 layoutTyVarBndr :: Bool -> ToBriDoc (HsTyVarBndr ())
@@ -973,7 +976,7 @@ layoutClsInst (L declLoc _) cid = do
         layouters <- mAsk
         layout_dataDecl
           layouters
-          (error "Unsupported form of DataFamInstDecl")
+          Nothing
           epAnn
           tycon
           (case bndrs of

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/Expr.hs

@@ -556,7 +556,10 @@ layoutExpr lexpr@(L _ expr) = do
       -- to making brittany idempotent, even though the result is non-optimal
       -- if "let" is moved horizontally as part of the transformation, as the
       -- comments before the first let item are moved horizontally with it.
-      letDoc  <- shareDoc $ wrapLet $ docLit $ Text.pack "let"
+      letDoc  <- shareDoc
+        $ docFlushCommsPost True spanLet
+        $ wrapLet
+        $ docLitS "let"
       inDoc   <- shareDoc $ wrapIn $ docLit $ Text.pack "in"
       docSetBaseAndIndent $ case fmap snd mBindDocs of
         Just [bindDoc] -> runFilteredAlternative $ do

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/OpTree.hs

@@ -198,6 +198,9 @@ layoutOpTree allowSinglelinePar = \case
           pure (pure op, subDoc)
     sharedOpsFlat <- flattenList docOps
     sharedOps     <- simpleTransform docOps
+    let lastWrap = if getPrec fixity <= 1
+          then docForceParSpacing
+          else docForceSingleline
     coreAlternative hasParen
                     locO
                     locC
@@ -205,11 +208,12 @@ layoutOpTree allowSinglelinePar = \case
                     docL
                     sharedOps
                     sharedOpsFlat
-                    docForceParSpacing
+                    lastWrap
   OpLeaf l -> pure l
  where
-  isPrec0 = \case
+  isPrec0 x = getPrec x == 0
-    Fixity _ prec _ -> prec == 0
+  getPrec = \case
+    Fixity _ prec _ -> prec
   coreAlternative
     :: Bool
     -> Maybe GHC.RealSrcLoc
@@ -223,7 +227,10 @@ layoutOpTree allowSinglelinePar = \case
   coreAlternative hasParen locO locC fixity docL sharedOps sharedOpsFlat lastWrap
     = do
       indentPolicy <- askLayoutConf _lconfig_indentPolicy
-      let wrapParenIfSl x inner = if x then wrapParenSl inner else docSetParSpacing inner
+      let zeroOps = null sharedOps
+          wrapParenIfSl x inner = if x
+            then wrapParenSl inner
+            else docSetParSpacing inner
           wrapParenSl inner = docAlt
             [ docSeq
               [ docLit $ Text.pack "("
@@ -241,7 +248,7 @@ layoutOpTree allowSinglelinePar = \case
           wrapParenMl innerHead innerLines = docSetBaseY $ docLines
             (  [ docCols
                    ColOpPrefix
-                   [ appSep $ docLit $ Text.pack "("
+                   [ (if zeroOps then id else appSep) $ docLit $ Text.pack "("
                    , docHandleComms locO $ innerHead
                    ]
                ]
@@ -268,7 +275,11 @@ layoutOpTree allowSinglelinePar = \case
               ([docForceSingleline docL] ++ case splitFirstLast sharedOpsFlat of
                 FirstLastEmpty -> []
                 FirstLastSingleton (od, ed) ->
-              [docSeparator, docForceSingleline od, docSeparator, lastWrap ed]
+                  [ docSeparator
+                  , docForceSingleline od
+                  , docSeparator
+                  , lastWrap ed
+                  ]
                 FirstLast (od1, ed1) ems (odN, edN) ->
                   (  [ docSeparator
                      , docForceSingleline od1
@@ -290,8 +301,6 @@ layoutOpTree allowSinglelinePar = \case
                      ]
                   )
               )
-        -- this case rather leads to some unfortunate layouting than to anything
-        -- useful; disabling for now. (it interfers with cols stuff.)
         -- one
         -- + two
         -- + three
@@ -311,8 +320,7 @@ layoutOpTree allowSinglelinePar = \case
           [(od, ed)] | curIsPrec0 ->
             addAlternativeCond (not hasParen && isSingleOp)
               $ docSetParSpacing
-              $ docPar
+              $ docPar (docHandleComms locO $ docForceSingleline $ docL)
-                (docHandleComms locO $ docForceSingleline $ docL)
                        (docSeq [od, docSeparator, singlelineUnlessFree ed])
           _ -> pure ()
         -- > ( one

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/Stmt.hs

@@ -47,18 +47,20 @@ layoutStmt lstmt@(L _ stmt) = do
           ]
         ]
     LetStmt epAnn binds -> docHandleComms epAnn $ do
+      let spanLet = obtainAnnPos epAnn AnnLet
+      letDoc <- shareDoc $ docFlushCommsPost True spanLet $ docLitS "let"
       let isFree = indentPolicy == IndentPolicyFree
       let indentFourPlus = indentAmount >= 4
       (wrapBinds, bindrDocsMay) <- callLayouter layout_localBinds binds
       case bindrDocsMay of
-        Nothing -> docLit $ Text.pack "let"
+        Nothing -> letDoc
           -- i just tested the above, and it is indeed allowed. heh.
-        Just (_, []) -> docLit $ Text.pack "let" -- this probably never happens
+        Just (_, []) -> letDoc -- this probably never happens
         Just (_, [bindDoc]) -> docAlt
           [ -- let bind = expr
             docCols
             ColDoLet
-            [ appSep $ docLit $ Text.pack "let"
+            [ appSep $ letDoc
             , let
                 f = case indentPolicy of
                   IndentPolicyFree -> docSetBaseAndIndent
@@ -71,7 +73,7 @@ layoutStmt lstmt@(L _ stmt) = do
           , -- let
             --   bind = expr
             docAddBaseY BrIndentRegular $ docPar
-            (docLit $ Text.pack "let")
+            letDoc
             (wrapBinds $ docSetBaseAndIndent $ return bindDoc)
           ]
         Just (_, bindDocs) -> runFilteredAlternative $ do
@@ -79,7 +81,7 @@ layoutStmt lstmt@(L _ stmt) = do
           --     bbb = exprb
           --     ccc = exprc
           addAlternativeCond (isFree || indentFourPlus) $ docSeq
-            [ appSep $ docLit $ Text.pack "let"
+            [ appSep $ letDoc
             , let
                 f = if indentFourPlus
                   then docEnsureIndent BrIndentRegular
@@ -93,7 +95,7 @@ layoutStmt lstmt@(L _ stmt) = do
           addAlternativeCond (not indentFourPlus)
             $ docAddBaseY BrIndentRegular
             $ docPar
-                (docLit $ Text.pack "let")
+                letDoc
                 (wrapBinds $ docSetBaseAndIndent $ docLines $ return <$> bindDocs)
     RecStmt epAnn (L _ stmts) _ _ _ _ _ ->
       docHandleComms epAnn $ runFilteredAlternative $ do

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/Type.hs

@@ -370,7 +370,9 @@ layoutType ltype@(L _ typ) = docHandleComms ltype $ case typ of
             ]
           )
       ]
-  HsBangTy{} -> -- TODO
+  HsBangTy epAnn (HsSrcBang NoSourceText NoSrcUnpack SrcStrict) innerTy -> do
+    docHandleComms epAnn $ docSeq [docLitS "!", layoutType innerTy]
+  HsBangTy {} ->
     briDocByExactInlineOnly "HsBangTy{}" ltype
   -- HsBangTy bang typ1 -> do
   --   let bangStr = case bang of

source/library/Language/Haskell/Brittany/Internal/Types.hs

@@ -24,6 +24,7 @@ import           GHC                            ( Anno
                                                 , ParsedSource
                                                 , XRec
                                                 , LImportDecl
+                                                , LEpaComment
                                                 )
 import GHC.Utils.Outputable(Outputable)
 import Language.Haskell.Brittany.Internal.Config.Types
@@ -52,7 +53,7 @@ data BrittanyError
   | forall ast . (Data.Data.Data (XRec GhcPs ast), Outputable (Anno ast)) => ErrorUnknownNode String (XRec GhcPs ast)
     -- ^ internal error: pretty-printing is not implemented for type of node
     --   in the syntax-tree
-  | ErrorOutputCheck
+  | ErrorOutputCheck String
     -- ^ checking the output for syntactic validity failed
 
 
@@ -89,6 +90,8 @@ finalToList_ :: FinalList a () -> [a]
 finalToList_ (FinalList l) = l (:) (\() -> [])
 finalToList :: FinalList a b -> ([a], b)
 finalToList (FinalList l) = l (\x (a, b) -> (x:a, b)) (\b -> ([], b))
+concatMapFinal :: FinalList a () -> (a -> [b]) -> [b]
+concatMapFinal (FinalList l) f = l (\x rest -> f x ++ rest) (\() -> [])
 
 instance Functor (FinalList a) where
   fmap = _finalRMap
@@ -119,7 +122,7 @@ data ModuleElement
     -- ^ an import decl, only occurs if pretty-printing the module head.
   | MEDecl (LHsDecl GhcPs) [(Int, EpaCommentTok)]
     -- ^ a top-level declaration
-  | MEComment (Int, EpaCommentTok)
+  | MEComment (Int, LEpaComment)
     -- ^ a top-level comment, i.e. a comment located between top-level elements
     --   (and not associated to some nested node, which might in theory happen).
     --   The Int carries the indentation of the comment.
@@ -236,7 +239,7 @@ data Layouters = Layouters
              )
          )
   , layout_dataDecl
-    :: GHC.LTyClDecl GhcPs
+    :: Maybe (GHC.LTyClDecl GhcPs)
     -> GHC.EpAnn [GHC.AddEpAnn]
     -> GHC.LIdP GhcPs
     -> GHC.LHsQTyVars GhcPs

source/library/Language/Haskell/Brittany/Internal/WriteBriDoc/Operators.hs

@@ -152,7 +152,7 @@ layoutWriteComment absolute isBlock dp commentLines s = do -- TODO92 we don't mo
   mSet state
     { _lstate_plannedSpace    = if isBlock
       then case _lstate_plannedSpace state of
-        PlannedNone         -> PlannedSameline 1
+        p@PlannedNone       -> p
         p@PlannedSameline{} -> p
         PlannedNewline l ->
           if l <= y then PlannedSameline 1 else PlannedNewline (l - y)

source/library/Language/Haskell/Brittany/Main.hs

@@ -381,9 +381,15 @@ coreIO putErrorLnIO config suppressOutput checkMode inputPathM outputPathM =
         putErrorLn left
         ExceptT.throwE 60
       Right (parsedSource, hasCPP) -> do
+        let moduleElementList = splitModuleDecls parsedSource
         (inlineConf, perItemConf) <- do
           resE <-
-            liftIO $ ExceptT.runExceptT $ extractCommentConfigs putErrorLnIO parsedSource
+            liftIO
+              $ ExceptT.runExceptT
+              $ extractCommentConfigs
+                putErrorLnIO
+                (extractDeclMap parsedSource)
+                moduleElementList
           case resE of
             Left (err, input) -> do
               putErrorLn $ "Error: parse error in inline configuration:"
@@ -414,9 +420,9 @@ coreIO putErrorLnIO config suppressOutput checkMode inputPathM outputPathM =
                     .> _econf_omit_output_valid_check
                     .> confUnpack
               (ews, outRaw) <- if hasCPP || omitCheck
-                then liftIO $ processModule (TraceFunc putErrorLnIO) moduleConf perItemConf parsedSource
+                then liftIO $ processModule (TraceFunc putErrorLnIO) moduleConf perItemConf moduleElementList
                 else liftIO
-                  $ pPrintModuleAndCheck (TraceFunc putErrorLnIO) moduleConf perItemConf parsedSource
+                  $ pPrintModuleAndCheck (TraceFunc putErrorLnIO) moduleConf perItemConf moduleElementList
               let
                 hackF s = fromMaybe s $ TextL.stripPrefix
                   (TextL.pack "-- BRITANY_INCLUDE_HACK ")

source/test-suite/Main.hs

@@ -15,6 +15,7 @@ import Language.Haskell.Brittany.Internal
 import Language.Haskell.Brittany.Internal.Config.Config
 import Language.Haskell.Brittany.Internal.Config.Types
 import Language.Haskell.Brittany.Internal.Prelude
+import Test.HUnit (assertEqual)
 import qualified System.Directory
 import System.FilePath ((</>))
 import System.Timeout (timeout)
@@ -22,6 +23,7 @@ import Test.Hspec
 import qualified Text.Parsec as Parsec
 import Text.Parsec.Text (Parser)
 import qualified Data.List.Extra
+import qualified System.Console.ANSI as ANSI
 
 hush :: Either a b -> Maybe b
 hush = either (const Nothing) Just
@@ -282,9 +284,15 @@ roundTripEqual c t =
     `shouldReturn` Right (PPTextWrapper t)
 
 goldenTest :: Config -> Text -> Text -> Expectation
-goldenTest c input expected =
+goldenTest c input expected = do
-  fmap (fmap PPTextWrapper) (parsePrintModuleTests c "TestFakeFileName.hs" input)
+  result <- parsePrintModuleTests c "TestFakeFileName.hs" input
-    `shouldReturn` Right (PPTextWrapper expected)
+  assertEqual
+    (  ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Dull ANSI.Red]
+    ++ "golden input: see test source!"
+    ++ ANSI.setSGRCode [ANSI.Reset]
+    )
+    (Right (PPTextWrapper expected))
+    (fmap PPTextWrapper result)
 
 newtype PPTextWrapper = PPTextWrapper Text
   deriving Eq
@@ -315,7 +323,7 @@ defaultTestConfig = Config
     , _lconfig_allowSingleLineExportList       = coerce True
     , _lconfig_allowHangingQuasiQuotes         = coerce True
     , _lconfig_experimentalSemicolonNewlines   = coerce False
-    -- , _lconfig_allowSinglelineRecord     = coerce False
+    , _lconfig_allowSinglelineRecord           = coerce False
     , _lconfig_fixityAwareOps                  = coerce True
     , _lconfig_fixityAwareTypeOps              = coerce True
     , _lconfig_fixityBasedAddAlignParens       = coerce False