diff --git a/.travis.yml b/.travis.yml
index 55adf2e..46b2763 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -73,9 +73,12 @@ matrix:
   - env: BUILD=cabal GHCVER=8.0.2 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
     compiler: ": #cabal 8.0.2"
     addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
-  - env: BUILD=cabal GHCVER=8.2.1 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
-    compiler: ": #cabal 8.2.1"
-    addons: {apt: {packages: [cabal-install-1.24,ghc-8.2.1,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+  - env: BUILD=cabal GHCVER=8.2.2 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #cabal 8.2.2"
+    addons: {apt: {packages: [cabal-install-1.24,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+  - env: BUILD=cabal GHCVER=8.4.1 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #cabal 8.4.1"
+    addons: {apt: {packages: [cabal-install-1.24,ghc-8.4.1,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
   # Build with the newest GHC and cabal-install. This is an accepted failure,
   # see below.
@@ -85,15 +88,15 @@ matrix:
 
   ##### CABAL DIST CHECK
 
-  - env: BUILD=cabaldist GHCVER=8.2.1 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
-    compiler: ": #cabal 8.2.1 dist"
-    addons: {apt: {packages: [cabal-install-1.24,ghc-8.2.1,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+  - env: BUILD=cabaldist GHCVER=8.2.2 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #cabal 8.2.2 dist"
+    addons: {apt: {packages: [cabal-install-1.24,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
   ##### CANEW #####
 
-  - env: BUILD=canew GHCVER=8.2.1 CABALVER=2.0 HAPPYVER=1.19.5 ALEXVER=3.1.7
-    compiler: ": #cabal new 8.2.1"
-    addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.1,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+  - env: BUILD=canew GHCVER=8.2.2 CABALVER=2.0 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #cabal new 8.2.2"
+    addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
   ##### STACK #####
 
@@ -118,6 +121,9 @@ matrix:
   - env: BUILD=stack ARGS="--stack-yaml stack-8.0.2.yaml"
     compiler: ": #stack 8.0.2"
     addons: {apt: {packages: [libgmp-dev]}}
+  - env: BUILD=stack ARGS="--stack-yaml stack-8.2.2.yaml"
+    compiler: ": #stack 8.2.2"
+    addons: {apt: {packages: [libgmp-dev]}}
 
   # Nightly builds are allowed to fail
   - env: BUILD=stack ARGS="--resolver nightly"
@@ -148,6 +154,7 @@ matrix:
   allow_failures:
   #- env: BUILD=cabal GHCVER=head  CABALVER=head HAPPYVER=1.19.5 ALEXVER=3.1.7
   - env: BUILD=stack ARGS="--resolver nightly"
+  - env: BUILD=stack ARGS=""
 
 before_install:
 # Using compiler above sets CC to an invalid value, so unset it
diff --git a/brittany.cabal b/brittany.cabal
index 4d99213..0d172c8 100644
--- a/brittany.cabal
+++ b/brittany.cabal
@@ -83,8 +83,8 @@ library {
     -j
   }
   build-depends:
-    { base >=4.9 && <4.11
-    , ghc >=8.0.1 && <8.3
+    { base >=4.9 && <4.12
+    , ghc >=8.0.1 && <8.5
     , ghc-paths >=0.1.0.9 && <0.2
     , ghc-exactprint >=0.5.6.0 && <0.5.7
     , transformers >=0.5.2.0 && <0.6
@@ -111,7 +111,7 @@ library {
     , semigroups >=0.18.2 && <0.19
     , cmdargs >=0.10.14 && <0.11
     , czipwith >=1.0.1.0 && <1.1
-    , ghc-boot-th >=8.0.1 && <8.3
+    , ghc-boot-th >=8.0.1 && <8.5
     , filepath >=1.4.1.0 && <1.5
     }
   default-extensions: {
diff --git a/src/Language/Haskell/Brittany/Internal.hs b/src/Language/Haskell/Brittany/Internal.hs
index b4a4525..d839fa3 100644
--- a/src/Language/Haskell/Brittany/Internal.hs
+++ b/src/Language/Haskell/Brittany/Internal.hs
@@ -52,7 +52,6 @@ import           Language.Haskell.Brittany.Internal.Transformations.Indent
 
 import qualified GHC as GHC hiding (parseModule)
 import           ApiAnnotation ( AnnKeywordId(..) )
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
 import           SrcLoc ( SrcSpan )
 import           HsSyn
@@ -436,7 +435,7 @@ toLocal conf anns m = do
   MultiRWSS.mGetRawW >>= \w -> MultiRWSS.mPutRawW (w <> write)
   pure x
 
-ppModule :: GenLocated SrcSpan (HsModule RdrName) -> PPM ()
+ppModule :: GenLocated SrcSpan (HsModule GhcPs) -> PPM ()
 ppModule lmod@(L _loc _m@(HsModule _name _exports _ decls _ _)) = do
   post <- ppPreamble lmod
   decls `forM_` \decl -> do
@@ -503,7 +502,7 @@ getDeclBindingNames (L _ decl) = case decl of
   _ -> []
 
 
-ppDecl :: LHsDecl RdrName -> PPMLocal ()
+ppDecl :: LHsDecl GhcPs -> PPMLocal ()
 ppDecl d@(L loc decl) = case decl of
   SigD sig -> -- trace (_sigHead sig) $
               withTransformedAnns d $ do
@@ -523,7 +522,7 @@ ppDecl d@(L loc decl) = case decl of
 
 -- Prints the information associated with the module annotation
 -- This includes the imports
-ppPreamble :: GenLocated SrcSpan (HsModule RdrName)
+ppPreamble :: GenLocated SrcSpan (HsModule GhcPs)
            -> PPM [(ExactPrint.KeywordId, ExactPrint.DeltaPos)]
 ppPreamble lmod@(L loc m@(HsModule _ _ _ _ _ _)) = do
   filteredAnns <- mAsk <&> \annMap ->
@@ -589,13 +588,13 @@ ppPreamble lmod@(L loc m@(HsModule _ _ _ _ _ _)) = do
       in  MultiRWSS.withMultiReader filteredAnns' $ processDefault emptyModule
   return post
 
-_sigHead :: Sig RdrName -> String
+_sigHead :: Sig GhcPs -> String
 _sigHead = \case
   TypeSig names _ ->
     "TypeSig " ++ intercalate "," (Text.unpack . lrdrNameToText <$> names)
   _ -> "unknown sig"
 
-_bindHead :: HsBind RdrName -> String
+_bindHead :: HsBind GhcPs -> String
 _bindHead = \case
   FunBind fId _ _ _ [] -> "FunBind " ++ (Text.unpack $ lrdrNameToText $ fId)
   PatBind _pat _ _ _ ([], []) -> "PatBind smth"
diff --git a/src/Language/Haskell/Brittany/Internal/Config.hs b/src/Language/Haskell/Brittany/Internal/Config.hs
index 6e87813..4c3d312 100644
--- a/src/Language/Haskell/Brittany/Internal/Config.hs
+++ b/src/Language/Haskell/Brittany/Internal/Config.hs
@@ -38,6 +38,7 @@ import           Language.Haskell.Brittany.Internal.Config.Types.Instances
 import           Language.Haskell.Brittany.Internal.Utils
 
 import           Data.Coerce ( Coercible, coerce )
+import qualified Data.List.NonEmpty as NonEmpty
 
 import qualified System.Directory as Directory
 import qualified System.FilePath.Posix as FilePath
@@ -272,7 +273,7 @@ readConfigs
   -> MaybeT IO Config
 readConfigs cmdlineConfig configPaths = do
   configs <- readConfig `mapM` configPaths
-  let merged = Semigroup.mconcat $ reverse (cmdlineConfig:catMaybes configs)
+  let merged = Semigroup.sconcat $ NonEmpty.reverse (cmdlineConfig :| catMaybes configs)
   return $ cZipWith fromOptionIdentity staticDefaultConfig merged
 
 -- | Reads provided configs
diff --git a/src/Language/Haskell/Brittany/Internal/ExactPrintUtils.hs b/src/Language/Haskell/Brittany/Internal/ExactPrintUtils.hs
index 749804c..19bc835 100644
--- a/src/Language/Haskell/Brittany/Internal/ExactPrintUtils.hs
+++ b/src/Language/Haskell/Brittany/Internal/ExactPrintUtils.hs
@@ -29,10 +29,9 @@ import qualified GHC           as GHC hiding (parseModule)
 import qualified Lexer         as GHC
 import qualified StringBuffer  as GHC
 import qualified Outputable    as GHC
-import           RdrName ( RdrName(..) )
+import qualified CmdLineParser as GHC
 import           HsSyn
 import           SrcLoc ( SrcSpan, Located )
-import           RdrName ( RdrName(..) )
 
 
 import qualified Language.Haskell.GHC.ExactPrint            as ExactPrint
@@ -79,7 +78,7 @@ parseModuleWithCpp cpp opts args fp dynCheck =
     when (not $ null warnings)
       $  ExceptT.throwE
       $  "when parsing ghc flags: encountered warnings: "
-      ++ show (warnings <&> \(L _ s) -> s)
+      ++ show (warnings <&> warnExtractorCompat)
     x   <- ExceptT.ExceptT $ liftIO $ dynCheck dflags2
     res <- lift $ ExactPrint.parseModuleApiAnnsWithCppInternal cpp dflags2 fp
     either (\(span, err) -> ExceptT.throwE $ show span ++ ": " ++ err)
@@ -111,7 +110,7 @@ parseModuleFromString args fp dynCheck str =
     when (not $ null warnings)
       $  ExceptT.throwE
       $  "when parsing ghc flags: encountered warnings: "
-      ++ show (warnings <&> \(L _ s) -> s)
+      ++ show (warnings <&> warnExtractorCompat)
     dynCheckRes <- ExceptT.ExceptT $ liftIO $ dynCheck dflags1
     let res = ExactPrint.parseModuleFromStringInternal dflags1 fp str
     case res of
@@ -187,7 +186,7 @@ commentAnnFixTransform modul = SYB.everything (>>) genF modul
  where
   genF :: Data.Data.Data a => a -> ExactPrint.Transform ()
   genF = (\_ -> return ()) `SYB.extQ` exprF
-  exprF :: Located (HsExpr RdrName) -> ExactPrint.Transform ()
+  exprF :: Located (HsExpr GhcPs) -> ExactPrint.Transform ()
   exprF lexpr@(L _ expr) = case expr of
     RecordCon _lname _ _ (HsRecFields fs@(_:_) Nothing) ->
       moveTrailingComments lexpr (List.last fs)
@@ -226,7 +225,7 @@ moveTrailingComments astFrom astTo = do
 -- elements to the relevant annotations. Avoids quadratic behaviour a trivial
 -- implementation would have.
 extractToplevelAnns
-  :: Located (HsModule RdrName)
+  :: Located (HsModule GhcPs)
   -> ExactPrint.Anns
   -> Map ExactPrint.AnnKey ExactPrint.Anns
 extractToplevelAnns lmod anns = output
@@ -265,3 +264,12 @@ foldedAnnKeys ast = SYB.everything
   )
   ast
   where locTyCon = SYB.typeRepTyCon (SYB.typeOf (L () ()))
+
+
+#if MIN_VERSION_ghc(8,4,0) /* ghc-8.4 */
+warnExtractorCompat :: GHC.Warn -> String
+warnExtractorCompat (GHC.Warn _ (L _ s)) = s
+#else /* ghc-8.0 && ghc-8.2 */
+warnExtractorCompat :: GenLocated l String -> String
+warnExtractorCompat (L _ s) = s
+#endif
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
index babcab1..53f58b7 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs
@@ -20,7 +20,6 @@ import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
 import           SrcLoc ( SrcSpan )
 import           HsSyn
@@ -88,11 +87,7 @@ layoutSig lsig@(L _loc sig) = case sig of
   InlineSig name (InlinePragma _ spec _arity phaseAct conlike) ->
     docWrapNode lsig $ do
       nameStr <- lrdrNameToTextAnn name
-      let specStr = case spec of
-            Inline          -> "INLINE "
-            Inlinable       -> "INLINABLE "
-            NoInline        -> "NOINLINE "
-            EmptyInlineSpec -> "" -- i have no idea if this is correct.
+      specStr <- specStringCompat lsig spec
       let phaseStr = case phaseAct of
             NeverActive      -> "" -- not [] - for NOINLINE NeverActive is
                                    -- in fact the default
@@ -108,7 +103,23 @@ layoutSig lsig@(L _loc sig) = case sig of
         <> Text.pack " #-}"
   _ -> briDocByExactNoComment lsig -- TODO
 
-layoutGuardLStmt :: ToBriDoc' (Stmt RdrName (LHsExpr RdrName))
+specStringCompat
+  :: MonadMultiWriter [BrittanyError] m => LSig GhcPs -> InlineSpec -> m String
+#if MIN_VERSION_ghc(8,4,0)
+specStringCompat ast = \case
+  NoUserInline    -> mTell [ErrorUnknownNode "NoUserInline" ast] $> ""
+  Inline          -> pure "INLINE "
+  Inlinable       -> pure "INLINABLE "
+  NoInline        -> pure "NOINLINE "
+#else
+specStringCompat _ = \case
+  Inline          -> pure "INLINE "
+  Inlinable       -> pure "INLINABLE "
+  NoInline        -> pure "NOINLINE "
+  EmptyInlineSpec -> pure ""
+#endif
+
+layoutGuardLStmt :: ToBriDoc' (Stmt GhcPs (LHsExpr GhcPs))
 layoutGuardLStmt lgstmt@(L _ stmtLR) = docWrapNode lgstmt $ case stmtLR of
   BodyStmt body _ _ _      -> layoutExpr body
   BindStmt lPat expr _ _ _ -> do
@@ -122,7 +133,7 @@ layoutGuardLStmt lgstmt@(L _ stmtLR) = docWrapNode lgstmt $ case stmtLR of
 
 layoutBind
   :: ToBriDocC
-       (HsBindLR RdrName RdrName)
+       (HsBindLR GhcPs GhcPs)
        (Either [BriDocNumbered] BriDocNumbered)
 layoutBind lbind@(L _ bind) = case bind of
   FunBind fId (MG lmatches@(L _ matches) _ _ _) _ _ [] -> do
@@ -148,15 +159,15 @@ layoutBind lbind@(L _ bind) = case bind of
                                                             hasComments
   _ -> Right <$> unknownNodeError "" lbind
 
-data BagBindOrSig = BagBind (LHsBindLR RdrName RdrName)
-                  | BagSig (LSig RdrName)
+data BagBindOrSig = BagBind (LHsBindLR GhcPs GhcPs)
+                  | BagSig (LSig GhcPs)
 
 bindOrSigtoSrcSpan :: BagBindOrSig -> SrcSpan
 bindOrSigtoSrcSpan (BagBind (L l _)) = l
 bindOrSigtoSrcSpan (BagSig  (L l _)) = l
 
 layoutLocalBinds
-  :: ToBriDocC (HsLocalBindsLR RdrName RdrName) (Maybe [BriDocNumbered])
+  :: ToBriDocC (HsLocalBindsLR GhcPs GhcPs) (Maybe [BriDocNumbered])
 layoutLocalBinds lbinds@(L _ binds) = case binds of
   -- HsValBinds (ValBindsIn lhsBindsLR []) ->
   --   Just . (>>= either id return) . Data.Foldable.toList <$> mapBagM layoutBind lhsBindsLR -- TODO: fix ordering
@@ -178,11 +189,11 @@ layoutLocalBinds lbinds@(L _ binds) = case binds of
   x@(HsIPBinds _ipBinds) -> Just . (:[]) <$> unknownNodeError "HsIPBinds" x
   EmptyLocalBinds        -> return $ Nothing
 
--- TODO: we don't need the `LHsExpr RdrName` anymore, now that there is
+-- TODO: we don't need the `LHsExpr GhcPs` anymore, now that there is
 -- parSpacing stuff.B
 layoutGrhs
-  :: LGRHS RdrName (LHsExpr RdrName)
-  -> ToBriDocM ([BriDocNumbered], BriDocNumbered, LHsExpr RdrName)
+  :: LGRHS GhcPs (LHsExpr GhcPs)
+  -> ToBriDocM ([BriDocNumbered], BriDocNumbered, LHsExpr GhcPs)
 layoutGrhs lgrhs@(L _ (GRHS guards body)) = do
   guardDocs <- docWrapNode lgrhs $ layoutStmt `mapM` guards
   bodyDoc   <- layoutExpr body
@@ -191,12 +202,14 @@ layoutGrhs lgrhs@(L _ (GRHS guards body)) = do
 layoutPatternBind
   :: Maybe Text
   -> BriDocNumbered
-  -> LMatch RdrName (LHsExpr RdrName)
+  -> LMatch GhcPs (LHsExpr GhcPs)
   -> ToBriDocM BriDocNumbered
-layoutPatternBind mIdStr binderDoc lmatch@(L _ match@(Match fixityOrCtx pats _ (GRHSs grhss whereBinds))) = do
+layoutPatternBind mIdStr binderDoc lmatch@(L _ match) = do
+  let pats                     = m_pats match
+  let (GRHSs grhss whereBinds) = m_grhss match
   patDocs <- pats `forM` \p -> fmap return $ colsWrapPat =<< layoutPat p
   let isInfix = isInfixMatch match
-  let mIdStr' = fixPatternBindIdentifier fixityOrCtx <$> mIdStr
+  let mIdStr' = fixPatternBindIdentifier match <$> mIdStr
   patDoc <- docWrapNodePrior lmatch $ case (mIdStr', patDocs) of
     (Just idStr, p1 : pr) | isInfix -> docCols
       ColPatternsFuncInfix
@@ -222,25 +235,26 @@ layoutPatternBind mIdStr binderDoc lmatch@(L _ match@(Match fixityOrCtx pats _ (
                          mWhereDocs
                          hasComments
 
-#if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */
+#if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 && ghc-8.4 */
 fixPatternBindIdentifier
-  :: HsMatchContext (NameOrRdrName RdrName) -> Text -> Text
-fixPatternBindIdentifier ctx idStr = case ctx of
-  (FunRhs _ _ SrcLazy    ) -> Text.cons '~' idStr
-  (FunRhs _ _ SrcStrict  ) -> Text.cons '!' idStr
-  (FunRhs _ _ NoSrcStrict) -> idStr
-  (StmtCtxt ctx1         ) -> fixPatternBindIdentifier' ctx1
-  _                        -> idStr
+  :: Match GhcPs (LHsExpr GhcPs) -> Text -> Text
+fixPatternBindIdentifier match idStr = go $ m_ctxt match
  where
+  go = \case
+    (FunRhs _ _ SrcLazy    ) -> Text.cons '~' idStr
+    (FunRhs _ _ SrcStrict  ) -> Text.cons '!' idStr
+    (FunRhs _ _ NoSrcStrict) -> idStr
+    (StmtCtxt ctx1         ) -> goInner ctx1
+    _                        -> idStr
   -- I have really no idea if this path ever occurs, but better safe than
   -- risking another "drop bangpatterns" bugs.
-  fixPatternBindIdentifier' = \case
-    (PatGuard      ctx1) -> fixPatternBindIdentifier ctx1 idStr
-    (ParStmtCtxt   ctx1) -> fixPatternBindIdentifier' ctx1
-    (TransStmtCtxt ctx1) -> fixPatternBindIdentifier' ctx1
+  goInner = \case
+    (PatGuard      ctx1) -> go ctx1
+    (ParStmtCtxt   ctx1) -> goInner ctx1
+    (TransStmtCtxt ctx1) -> goInner ctx1
     _                    -> idStr
-#else                      /* ghc-8.0 */
-fixPatternBindIdentifier :: MatchFixity RdrName -> Text -> Text
+#else                       /* ghc-8.0 */
+fixPatternBindIdentifier :: Match GhcPs (LHsExpr GhcPs) -> Text -> Text
 fixPatternBindIdentifier _ x = x
 #endif
 
@@ -248,7 +262,7 @@ layoutPatternBindFinal
   :: Maybe Text
   -> BriDocNumbered
   -> Maybe BriDocNumbered
-  -> [([BriDocNumbered], BriDocNumbered, LHsExpr RdrName)]
+  -> [([BriDocNumbered], BriDocNumbered, LHsExpr GhcPs)]
   -> Maybe [BriDocNumbered]
   -> Bool
   -> ToBriDocM BriDocNumbered
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs
index 9116c79..93a06ac 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs
@@ -15,8 +15,7 @@ import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName ( RdrName(..) )
-import           GHC ( runGhc, GenLocated(L), moduleNameString, AnnKeywordId(..) )
+import           GHC ( runGhc, GenLocated(L), moduleNameString, AnnKeywordId(..), RdrName(..) )
 import           HsSyn
 import           Name
 import qualified FastString
@@ -56,7 +55,12 @@ layoutExpr lexpr@(L _ expr) = do
       allocateNode $ overLitValBriDoc olit
     HsLit lit -> do
       allocateNode $ litBriDoc lit
-    HsLam (MG (L _ [lmatch@(L _ (Match _ pats _ (GRHSs [lgrhs@(L _ (GRHS [] body))] (L _ EmptyLocalBinds))))]) _ _ _) -> do
+    HsLam (MG (L _ [lmatch@(L _ match)]) _ _ _)
+      |  pats                  <- m_pats match
+      ,  GRHSs [lgrhs] llocals <- m_grhss match
+      ,  L _ EmptyLocalBinds   <- llocals
+      ,  L _ (GRHS [] body)    <- lgrhs
+      -> do
       patDocs <- pats `forM` \p -> fmap return $ colsWrapPat =<< layoutPat p
       bodyDoc <- docAddBaseY BrIndentRegular <$> docSharedWrapper layoutExpr body
       let funcPatternPartLine =
@@ -112,7 +116,7 @@ layoutExpr lexpr@(L _ expr) = do
         (docLit $ Text.pack "\\case")
         (docSetBaseAndIndent $ docNonBottomSpacing $ docLines $ return <$> funcPatDocs)
     HsApp exp1@(L _ HsApp{}) exp2 -> do
-      let gather :: [LHsExpr RdrName] -> LHsExpr RdrName -> (LHsExpr RdrName, [LHsExpr RdrName])
+      let gather :: [LHsExpr GhcPs] -> LHsExpr GhcPs -> (LHsExpr GhcPs, [LHsExpr GhcPs])
           gather list = \case
             L _ (HsApp l r) -> gather (r:list) l
             x               -> (x, list)
@@ -220,7 +224,7 @@ layoutExpr lexpr@(L _ expr) = do
       -- TODO
       briDocByExactInlineOnly "HsAppTypeOut{}" lexpr
     OpApp expLeft@(L _ OpApp{}) expOp _ expRight -> do
-      let gather :: [(LHsExpr RdrName, LHsExpr RdrName)] -> LHsExpr RdrName -> (LHsExpr RdrName, [(LHsExpr RdrName, LHsExpr RdrName)])
+      let gather :: [(LHsExpr GhcPs, LHsExpr GhcPs)] -> LHsExpr GhcPs -> (LHsExpr GhcPs, [(LHsExpr GhcPs, LHsExpr GhcPs)])
           gather opExprList = \case
             (L _ (OpApp l1 op1 _ r1)) -> gather ((op1, r1): opExprList) l1
             final -> (final, opExprList)
@@ -1077,7 +1081,31 @@ layoutExpr lexpr@(L _ expr) = do
 #endif
 
 
-#if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */
+#if MIN_VERSION_ghc(8,4,0) /* ghc-8.4 */
+litBriDoc :: HsLit GhcPs -> BriDocFInt
+litBriDoc = \case
+  HsChar       (SourceText t) _c                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ ['\'', c, '\'']
+  HsCharPrim   (SourceText t) _c                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ ['\'', c, '\'']
+  HsString     (SourceText t) _fastString                -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ FastString.unpackFS fastString
+  HsStringPrim (SourceText t) _byteString                -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ Data.ByteString.Char8.unpack byteString
+  HsInt        _              (IL (SourceText t) _ _)    -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsIntPrim    (SourceText t) _i                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsWordPrim   (SourceText t) _i                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsInt64Prim  (SourceText t) _i                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsWord64Prim (SourceText t) _i                         -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsInteger (SourceText t) _i                      _type -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ show i
+  HsRat     _              (FL (SourceText t) _ _) _type -> BDFLit $ Text.pack t
+  HsFloatPrim  _ (FL (SourceText t) _ _)                 -> BDFLit $ Text.pack t
+  HsDoublePrim _ (FL (SourceText t) _ _)                 -> BDFLit $ Text.pack t
+  _ -> error "litBriDoc: literal with no SourceText"
+
+overLitValBriDoc :: OverLitVal -> BriDocFInt
+overLitValBriDoc = \case
+  HsIntegral   (IL (SourceText t) _ _) -> BDFLit $ Text.pack t
+  HsFractional (FL (SourceText t) _ _) -> BDFLit $ Text.pack t
+  HsIsString (SourceText t) _ -> BDFLit $ Text.pack t
+  _ -> error "overLitValBriDoc: literal with no SourceText"
+#elif MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */
 litBriDoc :: HsLit -> BriDocFInt
 litBriDoc = \case
   HsChar       (SourceText t) _c          -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ ['\'', c, '\'']
@@ -1101,7 +1129,7 @@ overLitValBriDoc = \case
   HsFractional (FL t _) -> BDFLit $ Text.pack t
   HsIsString (SourceText t) _        -> BDFLit $ Text.pack t
   _ -> error "overLitValBriDoc: literal with no SourceText"
-#else
+#else                        /* ghc-8.0 */
 litBriDoc :: HsLit -> BriDocFInt
 litBriDoc = \case
   HsChar       t _c          -> BDFLit $ Text.pack t -- BDFLit $ Text.pack $ ['\'', c, '\'']
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs-boot b/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs-boot
index 0d01034..1f76032 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs-boot
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs-boot
@@ -14,7 +14,6 @@ where
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
 import           HsSyn
 import           Name
@@ -23,8 +22,12 @@ import           Name
 
 layoutExpr :: ToBriDoc HsExpr
 
--- layoutStmt :: ToBriDoc' (StmtLR RdrName RdrName (LHsExpr RdrName))
+-- layoutStmt :: ToBriDoc' (StmtLR GhcPs GhcPs (LHsExpr GhcPs))
 
+#if   MIN_VERSION_ghc(8,4,0) /* ghc-8.4 */
+litBriDoc :: HsLit GhcPs -> BriDocFInt
+#else /* ghc-8.0 && ghc-8.2 */
 litBriDoc :: HsLit -> BriDocFInt
+#endif
 
 overLitValBriDoc :: OverLitVal -> BriDocFInt
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/IE.hs b/src/Language/Haskell/Brittany/Internal/Layouters/IE.hs
index 2ba66a0..4e5af9f 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/IE.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/IE.hs
@@ -11,7 +11,6 @@ import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName (RdrName(..))
 import           GHC     ( unLoc
                          , runGhc
                          , GenLocated(L)
@@ -89,7 +88,7 @@ layoutIE lie@(L _ ie) = docWrapNode lie $ case ie of
 -- handling of the resulting list. Adding parens is
 -- left to the caller since that is context sensitive
 layoutAnnAndSepLLIEs
-  :: Located [LIE RdrName] -> ToBriDocM [ToBriDocM BriDocNumbered]
+  :: Located [LIE GhcPs] -> ToBriDocM [ToBriDocM BriDocNumbered]
 layoutAnnAndSepLLIEs llies@(L _ lies) = do
   let makeIENode ie = docSeq [docCommaSep, ie]
   let ieDocs = layoutIE <$> lies
@@ -114,7 +113,7 @@ layoutAnnAndSepLLIEs llies@(L _ lies) = do
 -- () -- no comments
 -- ( -- a comment
 -- )
-layoutLLIEs :: Bool -> Located [LIE RdrName] -> ToBriDocM BriDocNumbered
+layoutLLIEs :: Bool -> Located [LIE GhcPs] -> ToBriDocM BriDocNumbered
 layoutLLIEs enableSingleline llies = do
   ieDs        <- layoutAnnAndSepLLIEs llies
   hasComments <- hasAnyCommentsBelow llies
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Import.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Import.hs
index 7eb3e27..3f56dcd 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Import.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Import.hs
@@ -7,7 +7,6 @@ import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Layouters.IE
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName                                  ( RdrName(..) )
 import           GHC                                      ( unLoc
                                                           , GenLocated(L)
                                                           , moduleNameString
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Module.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Module.hs
index 1b7918d..2eebd20 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Module.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Module.hs
@@ -8,7 +8,6 @@ import           Language.Haskell.Brittany.Internal.Layouters.IE
 import           Language.Haskell.Brittany.Internal.Layouters.Import
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName (RdrName(..))
 import GHC (unLoc, runGhc, GenLocated(L), moduleNameString, AnnKeywordId(..))
 import           HsSyn
 import           Name
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Pattern.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Pattern.hs
index bf09e52..c65b357 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Pattern.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Pattern.hs
@@ -13,7 +13,6 @@ where
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 
-import           RdrName ( RdrName(..) )
 import           GHC ( Located, runGhc, GenLocated(L), moduleNameString )
 import           HsSyn
 import           Name
@@ -34,7 +33,7 @@ import           Language.Haskell.Brittany.Internal.Layouters.Type
 --        ^^^^^^^^^^ this part
 -- We will use `case .. of` as the imagined prefix to the examples used in
 -- the different cases below.
-layoutPat :: ToBriDocC (Pat RdrName) (Seq BriDocNumbered)
+layoutPat :: ToBriDocC (Pat GhcPs) (Seq BriDocNumbered)
 layoutPat lpat@(L _ pat) = docWrapNode lpat $ case pat of
   WildPat _  -> fmap Seq.singleton $ docLit $ Text.pack "_"
     -- _ -> expr
@@ -199,7 +198,7 @@ colsWrapPat :: Seq BriDocNumbered -> ToBriDocM BriDocNumbered
 colsWrapPat = docCols ColPatterns . fmap return . Foldable.toList
 
 wrapPatPrepend
-  :: Located (Pat RdrName)
+  :: Located (Pat GhcPs)
   -> ToBriDocM BriDocNumbered
   -> ToBriDocM (Seq BriDocNumbered)
 wrapPatPrepend pat prepElem = do
@@ -211,7 +210,7 @@ wrapPatPrepend pat prepElem = do
       return $ x1' Seq.<| xR
 
 wrapPatListy
-  :: [Located (Pat RdrName)]
+  :: [Located (Pat GhcPs)]
   -> String
   -> String
   -> ToBriDocM (Seq BriDocNumbered)
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
index 4128aea..70daf6c 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
@@ -13,7 +13,6 @@ import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
 import           HsSyn
 import           Name
@@ -26,7 +25,7 @@ import {-# SOURCE #-} Language.Haskell.Brittany.Internal.Layouters.Expr
 
 
 
-layoutStmt :: ToBriDoc' (StmtLR RdrName RdrName (LHsExpr RdrName))
+layoutStmt :: ToBriDoc' (StmtLR GhcPs GhcPs (LHsExpr GhcPs))
 layoutStmt lstmt@(L _ stmt) = do
   indentPolicy <- mAsk <&> _conf_layout .> _lconfig_indentPolicy .> confUnpack
   docWrapNode lstmt $ case stmt of
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs-boot b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs-boot
index 0cb46be..faf583a 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs-boot
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs-boot
@@ -12,7 +12,6 @@ where
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
 import           HsSyn
 import           Name
@@ -21,4 +20,4 @@ import           BasicTypes
 
 
 
-layoutStmt :: ToBriDoc' (StmtLR RdrName RdrName (LHsExpr RdrName))
+layoutStmt :: ToBriDoc' (StmtLR GhcPs GhcPs (LHsExpr GhcPs))
diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Type.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Type.hs
index 646f986..dfde7f5 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Type.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Type.hs
@@ -13,7 +13,6 @@ import           Language.Haskell.Brittany.Internal.Config.Types
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 
-import           RdrName ( RdrName(..) )
 import           GHC ( runGhc
                      , GenLocated(L)
                      , moduleNameString
diff --git a/src/Language/Haskell/Brittany/Internal/Prelude.hs b/src/Language/Haskell/Brittany/Internal/Prelude.hs
index dbd4b52..2d8a038 100644
--- a/src/Language/Haskell/Brittany/Internal/Prelude.hs
+++ b/src/Language/Haskell/Brittany/Internal/Prelude.hs
@@ -1,8 +1,24 @@
-module Language.Haskell.Brittany.Internal.Prelude (module E)
+module Language.Haskell.Brittany.Internal.Prelude
+  ( module E
+  , module Language.Haskell.Brittany.Internal.Prelude
+  )
 where
 
 
 
+-- rather project-specific stuff:
+---------------------------------
+#if MIN_VERSION_ghc(8,4,0) /* ghc-8.4 */
+import HsExtension                    as E ( GhcPs )
+#endif
+
+import RdrName                        as E ( RdrName )
+
+
+
+-- more general:
+----------------
+
 import Data.Functor.Identity         as E ( Identity(..) )
 import Control.Concurrent.Chan       as E ( Chan )
 import Control.Concurrent.MVar       as E ( MVar )
@@ -379,3 +395,10 @@ import Control.Monad.Trans.Maybe     as E ( MaybeT (..)
 import Data.Data                     as E ( toConstr
                                           )
 
+todo :: a
+todo = error "todo"
+
+
+#if !MIN_VERSION_ghc(8,4,0) /* ghc-8.0, ghc-8.2 */
+type GhcPs = RdrName
+#endif
diff --git a/src/Language/Haskell/Brittany/Internal/Types.hs b/src/Language/Haskell/Brittany/Internal/Types.hs
index a0716da..a28f940 100644
--- a/src/Language/Haskell/Brittany/Internal/Types.hs
+++ b/src/Language/Haskell/Brittany/Internal/Types.hs
@@ -17,7 +17,6 @@ import qualified Language.Haskell.GHC.ExactPrint.Types as ExactPrint.Types
 
 import qualified Data.Text.Lazy.Builder as Text.Builder
 
-import           RdrName ( RdrName(..) )
 import           GHC ( Located, runGhc, GenLocated(L), moduleNameString, AnnKeywordId )
 
 import           Language.Haskell.GHC.ExactPrint ( AnnKey, Comment )
@@ -205,9 +204,9 @@ data BrIndent = BrIndentNone
 
 type ToBriDocM = MultiRWSS.MultiRWS '[Config, Anns] '[[BrittanyError], Seq String] '[NodeAllocIndex]
 
-type ToBriDoc (sym :: * -> *) = Located (sym RdrName) -> ToBriDocM BriDocNumbered
-type ToBriDoc' sym            = Located sym           -> ToBriDocM BriDocNumbered
-type ToBriDocC sym c          = Located sym           -> ToBriDocM c
+type ToBriDoc (sym :: * -> *) = Located (sym GhcPs) -> ToBriDocM BriDocNumbered
+type ToBriDoc' sym            = Located sym         -> ToBriDocM BriDocNumbered
+type ToBriDocC sym c          = Located sym         -> ToBriDocM c
 
 data DocMultiLine
   = MultiLineNo