diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index a5647ae..4b8343e 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -8,9 +8,9 @@
 #
 # For more information, see https://github.com/haskell-CI/haskell-ci
 #
-# version: 0.12
+# version: 0.13.20211030
 #
-# REGENDATA ("0.12",["github","cabal.project"])
+# REGENDATA ("0.13.20211030",["github","cabal.project"])
 #
 name: Haskell-CI
 on:
@@ -35,50 +35,96 @@ jobs:
     strategy:
       matrix:
         include:
+          - compiler: ghc-9.2.1
+            compilerKind: ghc
+            compilerVersion: 9.2.1
+            setup-method: ghcup
+            allow-failure: false
           - compiler: ghc-9.0.1
+            compilerKind: ghc
+            compilerVersion: 9.0.1
+            setup-method: hvr-ppa
             allow-failure: false
             upload: true
           - compiler: ghc-8.10.4
+            compilerKind: ghc
+            compilerVersion: 8.10.4
+            setup-method: hvr-ppa
             allow-failure: false
           - compiler: ghc-8.8.4
+            compilerKind: ghc
+            compilerVersion: 8.8.4
+            setup-method: hvr-ppa
             allow-failure: false
           - compiler: ghc-8.6.5
+            compilerKind: ghc
+            compilerVersion: 8.6.5
+            setup-method: hvr-ppa
             allow-failure: false
           - compiler: ghc-8.4.4
+            compilerKind: ghc
+            compilerVersion: 8.4.4
+            setup-method: hvr-ppa
             allow-failure: false
       fail-fast: false
     steps:
       - name: apt
         run: |
           apt-get update
-          apt-get install -y --no-install-recommends gnupg ca-certificates dirmngr curl git software-properties-common
-          apt-add-repository -y 'ppa:hvr/ghc'
-          apt-get update
-          apt-get install -y $CC cabal-install-3.4 libx11-dev libxext-dev libxinerama-dev libxrandr-dev libxss-dev
+          apt-get install -y --no-install-recommends gnupg ca-certificates dirmngr curl git software-properties-common libtinfo5
+          if [ "${{ matrix.setup-method }}" = ghcup ]; then
+            mkdir -p "$HOME/.ghcup/bin"
+            curl -sL https://downloads.haskell.org/ghcup/0.1.17.3/x86_64-linux-ghcup-0.1.17.3 > "$HOME/.ghcup/bin/ghcup"
+            chmod a+x "$HOME/.ghcup/bin/ghcup"
+            "$HOME/.ghcup/bin/ghcup" install ghc "$HCVER"
+            "$HOME/.ghcup/bin/ghcup" install cabal 3.6.2.0
+            apt-get update
+            apt-get install -y libx11-dev libxext-dev libxinerama-dev libxrandr-dev libxss-dev
+          else
+            apt-add-repository -y 'ppa:hvr/ghc'
+            apt-get update
+            apt-get install -y "$HCNAME" libx11-dev libxext-dev libxinerama-dev libxrandr-dev libxss-dev
+            mkdir -p "$HOME/.ghcup/bin"
+            curl -sL https://downloads.haskell.org/ghcup/0.1.17.3/x86_64-linux-ghcup-0.1.17.3 > "$HOME/.ghcup/bin/ghcup"
+            chmod a+x "$HOME/.ghcup/bin/ghcup"
+            "$HOME/.ghcup/bin/ghcup" install cabal 3.6.2.0
+          fi
         env:
-          CC: ${{ matrix.compiler }}
+          HCKIND: ${{ matrix.compilerKind }}
+          HCNAME: ${{ matrix.compiler }}
+          HCVER: ${{ matrix.compilerVersion }}
       - name: Set PATH and environment variables
         run: |
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
-          echo "LANG=C.UTF-8" >> $GITHUB_ENV
-          echo "CABAL_DIR=$HOME/.cabal" >> $GITHUB_ENV
-          echo "CABAL_CONFIG=$HOME/.cabal/config" >> $GITHUB_ENV
-          HCDIR=$(echo "/opt/$CC" | sed 's/-/\//')
-          HCNAME=ghc
-          HC=$HCDIR/bin/$HCNAME
-          echo "HC=$HC" >> $GITHUB_ENV
-          echo "HCPKG=$HCDIR/bin/$HCNAME-pkg" >> $GITHUB_ENV
-          echo "HADDOCK=$HCDIR/bin/haddock" >> $GITHUB_ENV
-          echo "CABAL=/opt/cabal/3.4/bin/cabal -vnormal+nowrap" >> $GITHUB_ENV
+          echo "LANG=C.UTF-8" >> "$GITHUB_ENV"
+          echo "CABAL_DIR=$HOME/.cabal" >> "$GITHUB_ENV"
+          echo "CABAL_CONFIG=$HOME/.cabal/config" >> "$GITHUB_ENV"
+          HCDIR=/opt/$HCKIND/$HCVER
+          if [ "${{ matrix.setup-method }}" = ghcup ]; then
+            HC=$HOME/.ghcup/bin/$HCKIND-$HCVER
+            echo "HC=$HC" >> "$GITHUB_ENV"
+            echo "HCPKG=$HOME/.ghcup/bin/$HCKIND-pkg-$HCVER" >> "$GITHUB_ENV"
+            echo "HADDOCK=$HOME/.ghcup/bin/haddock-$HCVER" >> "$GITHUB_ENV"
+            echo "CABAL=$HOME/.ghcup/bin/cabal-3.6.2.0 -vnormal+nowrap" >> "$GITHUB_ENV"
+          else
+            HC=$HCDIR/bin/$HCKIND
+            echo "HC=$HC" >> "$GITHUB_ENV"
+            echo "HCPKG=$HCDIR/bin/$HCKIND-pkg" >> "$GITHUB_ENV"
+            echo "HADDOCK=$HCDIR/bin/haddock" >> "$GITHUB_ENV"
+            echo "CABAL=$HOME/.ghcup/bin/cabal-3.6.2.0 -vnormal+nowrap" >> "$GITHUB_ENV"
+          fi
+
           HCNUMVER=$(${HC} --numeric-version|perl -ne '/^(\d+)\.(\d+)\.(\d+)(\.(\d+))?$/; print(10000 * $1 + 100 * $2 + ($3 == 0 ? $5 != 1 : $3))')
-          echo "HCNUMVER=$HCNUMVER" >> $GITHUB_ENV
-          echo "ARG_TESTS=--enable-tests" >> $GITHUB_ENV
-          echo "ARG_BENCH=--enable-benchmarks" >> $GITHUB_ENV
-          echo "HEADHACKAGE=false" >> $GITHUB_ENV
-          echo "ARG_COMPILER=--$HCNAME --with-compiler=$HC" >> $GITHUB_ENV
-          echo "GHCJSARITH=0" >> $GITHUB_ENV
+          echo "HCNUMVER=$HCNUMVER" >> "$GITHUB_ENV"
+          echo "ARG_TESTS=--enable-tests" >> "$GITHUB_ENV"
+          echo "ARG_BENCH=--enable-benchmarks" >> "$GITHUB_ENV"
+          echo "HEADHACKAGE=false" >> "$GITHUB_ENV"
+          echo "ARG_COMPILER=--$HCKIND --with-compiler=$HC" >> "$GITHUB_ENV"
+          echo "GHCJSARITH=0" >> "$GITHUB_ENV"
         env:
-          CC: ${{ matrix.compiler }}
+          HCKIND: ${{ matrix.compilerKind }}
+          HCNAME: ${{ matrix.compiler }}
+          HCVER: ${{ matrix.compilerVersion }}
       - name: env
         run: |
           env
@@ -139,7 +185,8 @@ jobs:
       - name: generate cabal.project
         run: |
           PKGDIR_xmonad="$(find "$GITHUB_WORKSPACE/unpacked" -maxdepth 1 -type d -regex '.*/xmonad-[0-9.]*')"
-          echo "PKGDIR_xmonad=${PKGDIR_xmonad}" >> $GITHUB_ENV
+          echo "PKGDIR_xmonad=${PKGDIR_xmonad}" >> "$GITHUB_ENV"
+          rm -f cabal.project cabal.project.local
           touch cabal.project
           touch cabal.project.local
           echo "packages: ${PKGDIR_xmonad}" >> cabal.project
diff --git a/src/XMonad/Core.hs b/src/XMonad/Core.hs
index 46a0939..f02081e 100644
--- a/src/XMonad/Core.hs
+++ b/src/XMonad/Core.hs
@@ -156,18 +156,13 @@ newtype ScreenDetail = SD { screenRect :: Rectangle }
 -- instantiated on 'XConf' and 'XState' automatically.
 --
 newtype X a = X (ReaderT XConf (StateT XState IO) a)
-    deriving (Functor, Monad, MonadFail, MonadIO, MonadState XState, MonadReader XConf)
-
-instance Applicative X where
-  pure = return
-  (<*>) = ap
+    deriving (Functor, Applicative, Monad, MonadFail, MonadIO, MonadState XState, MonadReader XConf)
 
 instance Semigroup a => Semigroup (X a) where
     (<>) = liftM2 (<>)
 
 instance (Monoid a) => Monoid (X a) where
-    mempty  = return mempty
-    mappend = liftM2 mappend
+    mempty = pure mempty
 
 instance Default a => Default (X a) where
     def = return def
@@ -183,8 +178,7 @@ instance Semigroup a => Semigroup (Query a) where
     (<>) = liftM2 (<>)
 
 instance Monoid a => Monoid (Query a) where
-    mempty  = return mempty
-    mappend = liftM2 mappend
+    mempty = pure mempty
 
 instance Default a => Default (Query a) where
     def = return def
diff --git a/src/XMonad/Main.hs b/src/XMonad/Main.hs
index 75a388d..da1d1f7 100644
--- a/src/XMonad/Main.hs
+++ b/src/XMonad/Main.hs
@@ -193,12 +193,12 @@ launch initxmc drs = do
 
     xinesc <- getCleanedScreenInfo dpy
 
-    nbc    <- do v            <- initColor dpy $ normalBorderColor  xmc
-                 ~(Just nbc_) <- initColor dpy $ normalBorderColor Default.def
+    nbc    <- do v         <- initColor dpy $ normalBorderColor  xmc
+                 Just nbc_ <- initColor dpy $ normalBorderColor Default.def
                  return (fromMaybe nbc_ v)
 
     fbc    <- do v <- initColor dpy $ focusedBorderColor xmc
-                 ~(Just fbc_)  <- initColor dpy $ focusedBorderColor Default.def
+                 Just fbc_ <- initColor dpy $ focusedBorderColor Default.def
                  return (fromMaybe fbc_ v)
 
     hSetBuffering stdout NoBuffering
diff --git a/src/XMonad/Operations.hs b/src/XMonad/Operations.hs
index 2458a71..0de274a 100644
--- a/src/XMonad/Operations.hs
+++ b/src/XMonad/Operations.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE FlexibleContexts, FlexibleInstances, MultiParamTypeClasses, PatternGuards #-}
+{-# LANGUAGE FlexibleContexts, FlexibleInstances, MultiParamTypeClasses, PatternGuards, LambdaCase #-}
 -- --------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Operations
@@ -341,15 +341,16 @@ getCleanedScreenInfo = io .  fmap nubScreens . getScreenInfo
 -- | The screen configuration may have changed (due to -- xrandr),
 -- update the state and refresh the screen, and reset the gap.
 rescreen :: X ()
-rescreen = do
-    xinesc <- withDisplay getCleanedScreenInfo
-
-    windows $ \ws@(W.StackSet { W.current = v, W.visible = vs, W.hidden = hs }) ->
-        let (xs, ys) = splitAt (length xinesc) $ map W.workspace (v:vs) ++ hs
-            (a:as)   = zipWith3 W.Screen xs [0..] $ map SD xinesc
-        in  ws { W.current = a
-               , W.visible = as
-               , W.hidden  = ys }
+rescreen = withDisplay getCleanedScreenInfo >>= \case
+    [] -> trace "getCleanedScreenInfo returned []"
+    xinesc:xinescs ->
+        windows $ \ws@W.StackSet{ W.current = v, W.visible = vs, W.hidden = hs } ->
+            let (xs, ys) = splitAt (length xinescs) (map W.workspace vs ++ hs)
+                a = W.Screen (W.workspace v) 0 (SD xinesc)
+                as = zipWith3 W.Screen xs [1..] $ map SD xinescs
+            in  ws { W.current = a
+                   , W.visible = as
+                   , W.hidden  = ys }
 
 -- ---------------------------------------------------------------------
 
diff --git a/src/XMonad/StackSet.hs b/src/XMonad/StackSet.hs
index 7fe0d1a..fef07ba 100644
--- a/src/XMonad/StackSet.hs
+++ b/src/XMonad/StackSet.hs
@@ -58,6 +58,8 @@ import Data.Foldable (foldr, toList)
 import Data.Maybe   (listToMaybe,isJust,fromMaybe)
 import qualified Data.List as L (deleteBy,find,splitAt,filter,nub)
 import Data.List ( (\\) )
+import qualified Data.List.NonEmpty as NE
+import Data.List.NonEmpty (NonEmpty((:|)))
 import qualified Data.Map  as M (Map,insert,delete,empty)
 
 -- $intro
@@ -208,10 +210,11 @@ abort x = error $ "xmonad: StackSet: " ++ x
 -- Xinerama: Virtual workspaces are assigned to physical screens, starting at 0.
 --
 new :: (Integral s) => l -> [i] -> [sd] -> StackSet i l a s sd
-new l wids m | not (null wids) && length m <= length wids && not (null m)
-  = StackSet cur visi unseen M.empty
-  where (seen,unseen) = L.splitAt (length m) $ map (\i -> Workspace i l Nothing) wids
-        (cur:visi)    = [ Screen i s sd |  (i, s, sd) <- zip3 seen [0..] m ]
+new l (wid:wids) (m:ms) | length ms <= length wids
+  = StackSet cur visi (map ws unseen) M.empty
+  where ws i = Workspace i l Nothing
+        (seen, unseen) = L.splitAt (length ms) wids
+        cur:visi = Screen (ws wid) 0 m : [ Screen (ws i) s sd | (i, s, sd) <- zip3 seen [1..] ms ]
                 -- now zip up visibles with their screen id
 new _ _ _ = abort "non-positive argument to StackSet.new"
 
@@ -366,7 +369,7 @@ swapDown  = modify' (reverseStack . swapUp' . reverseStack)
 -- 'Stack' rather than an entire 'StackSet'.
 focusUp', focusDown' :: Stack a -> Stack a
 focusUp' (Stack t (l:ls) rs) = Stack l ls (t:rs)
-focusUp' (Stack t []     rs) = Stack x xs [] where (x:xs) = reverse (t:rs)
+focusUp' (Stack t []     rs) = Stack x xs [] where (x :| xs) = NE.reverse (t :| rs)
 focusDown'                   = reverseStack . focusUp' . reverseStack
 
 swapUp' :: Stack a -> Stack a
@@ -522,8 +525,8 @@ sink w s = s { floating = M.delete w (floating s) }
 -- Focus stays with the item moved.
 swapMaster :: StackSet i l a s sd -> StackSet i l a s sd
 swapMaster = modify' $ \c -> case c of
-    Stack _ [] _  -> c    -- already master.
-    Stack t ls rs -> Stack t [] (xs ++ x : rs) where (x:xs) = reverse ls
+    Stack _ []     _  -> c    -- already master.
+    Stack t (l:ls) rs -> Stack t [] (xs ++ x : rs) where (x :| xs) = NE.reverse (l :| ls)
 
 -- natural! keep focus, move current to the top, move top to current.
 
@@ -539,8 +542,8 @@ shiftMaster = modify' $ \c -> case c of
 -- | /O(s)/. Set focus to the master window.
 focusMaster :: StackSet i l a s sd -> StackSet i l a s sd
 focusMaster = modify' $ \c -> case c of
-    Stack _ [] _  -> c
-    Stack t ls rs -> Stack x [] (xs ++ t : rs) where (x:xs) = reverse ls
+    Stack _ []     _  -> c
+    Stack t (l:ls) rs -> Stack x [] (xs ++ t : rs) where (x :| xs) = NE.reverse (l :| ls)
 
 --
 -- ---------------------------------------------------------------------
diff --git a/xmonad.cabal b/xmonad.cabal
index 3cf79b7..dc4ef49 100644
--- a/xmonad.cabal
+++ b/xmonad.cabal
@@ -27,7 +27,7 @@ author:             Spencer Janssen, Don Stewart, Adam Vogt, David Roundy, Jason
                     Ondřej Súkup, Paul Hebble, Shachaf Ben-Kiki, Siim Põder, Tim McIver,
                     Trevor Elliott, Wouter Swierstra, Conrad Irwin, Tim Thelion
 maintainer:         xmonad@haskell.org
-tested-with:        GHC == 8.4.4 || == 8.6.5 || == 8.8.4 || == 8.10.4 || == 9.0.1
+tested-with:        GHC == 8.4.4 || == 8.6.5 || == 8.8.4 || == 8.10.4 || == 9.0.1 || == 9.2.1
 category:           System
 homepage:           http://xmonad.org
 bug-reports:        https://github.com/xmonad/xmonad/issues