Misc cleanup

- Use dedicated list functions
- Make cloneBndrs and cloneRecIdBndrs monadic
- Fix invalid haddock comments in libraries/base

13 files changed, 30 insertions, 33 deletions

diff --git a/compiler/GHC/CmmToAsm/X86/CodeGen.hs b/compiler/GHC/CmmToAsm/X86/CodeGen.hs
index bf1c36bf55..d6ef821c9f 100644
--- a/compiler/GHC/CmmToAsm/X86/CodeGen.hs
+++ b/compiler/GHC/CmmToAsm/X86/CodeGen.hs
@@ -2715,7 +2715,7 @@ genCCall64 addr conv dest_regs args = do
                <- load_args prom_args (allIntArgRegs platform)
                                       (allFPArgRegs platform)
                                       nilOL nilOL
-           let used_regs rs as = reverse (drop (length rs) (reverse as))
+           let used_regs rs as = dropTail (length rs) as
                fregs_used      = used_regs fregs (allFPArgRegs platform)
                aregs_used      = used_regs aregs (allIntArgRegs platform)
            return (stack_args, aregs_used, fregs_used, load_args_code
diff --git a/compiler/GHC/Core/Make.hs b/compiler/GHC/Core/Make.hs
index c11f84d9ba..a0f659f318 100644
--- a/compiler/GHC/Core/Make.hs
+++ b/compiler/GHC/Core/Make.hs
@@ -556,7 +556,8 @@ chunkify xs
   where
     n_xs     = length xs
     split [] = []
-    split xs = take mAX_TUPLE_SIZE xs : split (drop mAX_TUPLE_SIZE xs)
+    split xs = let (as, bs) = splitAt mAX_TUPLE_SIZE xs
+               in as : split bs
 
 
 {-
diff --git a/compiler/GHC/Core/Opt/SetLevels.hs b/compiler/GHC/Core/Opt/SetLevels.hs
index 95084cf7b6..bcd01bec04 100644
--- a/compiler/GHC/Core/Opt/SetLevels.hs
+++ b/compiler/GHC/Core/Opt/SetLevels.hs
@@ -1752,13 +1752,12 @@ newLvlVar lvld_rhs join_arity_maybe is_mk_static
 cloneCaseBndrs :: LevelEnv -> Level -> [Var] -> LvlM (LevelEnv, [Var])
 cloneCaseBndrs env@(LE { le_subst = subst, le_lvl_env = lvl_env, le_env = id_env })
                new_lvl vs
-  = do { us <- getUniqueSupplyM
-       ; let (subst', vs') = cloneBndrs subst us vs
+  = do { (subst', vs') <- cloneBndrs subst vs
              -- N.B. We are not moving the body of the case, merely its case
              -- binders.  Consequently we should *not* set le_ctxt_lvl and
              -- le_join_ceil.  See Note [Setting levels when floating
              -- single-alternative cases].
-             env' = env { le_lvl_env   = addLvls new_lvl lvl_env vs'
+       ; let env' = env { le_lvl_env   = addLvls new_lvl lvl_env vs'
                         , le_subst     = subst'
                         , le_env       = foldl' add_id id_env (vs `zip` vs') }
 
@@ -1773,13 +1772,13 @@ cloneLetVars :: RecFlag -> LevelEnv -> Level -> [InVar]
 cloneLetVars is_rec
           env@(LE { le_subst = subst, le_lvl_env = lvl_env, le_env = id_env })
           dest_lvl vs
-  = do { us <- getUniqueSupplyM
-       ; let vs1  = map zap vs
+  = do { let vs1  = map zap vs
                       -- See Note [Zapping the demand info]
-             (subst', vs2) = case is_rec of
-                               NonRecursive -> cloneBndrs      subst us vs1
-                               Recursive    -> cloneRecIdBndrs subst us vs1
-             prs  = vs `zip` vs2
+       ; (subst', vs2) <- case is_rec of
+                            NonRecursive -> cloneBndrs      subst vs1
+                            Recursive    -> cloneRecIdBndrs subst vs1
+
+       ; let prs  = vs `zip` vs2
              env' = env { le_lvl_env = addLvls dest_lvl lvl_env vs2
                         , le_subst   = subst'
                         , le_env     = foldl' add_id id_env prs }
diff --git a/compiler/GHC/Core/Opt/Specialise.hs b/compiler/GHC/Core/Opt/Specialise.hs
index cfeaf59649..826bb96d4a 100644
--- a/compiler/GHC/Core/Opt/Specialise.hs
+++ b/compiler/GHC/Core/Opt/Specialise.hs
@@ -3461,9 +3461,8 @@ cloneBndrSM env@(SE { se_subst = subst }) bndr
 
 cloneRecBndrsSM :: SpecEnv -> [Id] -> SpecM (SpecEnv, [Id])
 cloneRecBndrsSM env@(SE { se_subst = subst }) bndrs
-  = do { us <- getUniqueSupplyM
-       ; let (subst', bndrs') = Core.cloneRecIdBndrs subst us bndrs
-             env' = env { se_subst = subst' }
+  = do { (subst', bndrs') <- Core.cloneRecIdBndrs subst bndrs
+       ; let env' = env { se_subst = subst' }
        ; return (env', bndrs') }
 
 newDictBndr :: SpecEnv -> CoreBndr -> SpecM (SpecEnv, CoreBndr)
diff --git a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
index 488eeaf5f4..7eb68556fd 100644
--- a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
+++ b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
@@ -213,12 +213,11 @@ mkWwBodies opts fun_id arg_vars res_ty demands res_cpr
         -- Clone and prepare arg_vars of the original fun RHS
         -- See Note [Freshen WW arguments]
         -- and Note [Zap IdInfo on worker args]
-        ; uniq_supply <- getUniqueSupplyM
         ; let args_free_tcvs = tyCoVarsOfTypes (res_ty : map varType arg_vars)
               empty_subst = mkEmptySubst (mkInScopeSet args_free_tcvs)
               zapped_arg_vars = map zap_var arg_vars
-              (subst, cloned_arg_vars) = cloneBndrs empty_subst uniq_supply zapped_arg_vars
-              res_ty' = substTyUnchecked subst res_ty
+        ; (subst, cloned_arg_vars) <- cloneBndrs empty_subst zapped_arg_vars
+        ; let res_ty' = substTyUnchecked subst res_ty
               init_str_marks = map (const NotMarkedStrict) cloned_arg_vars
 
         ; (useful1, work_args_str, wrap_fn_str, fn_args)
diff --git a/compiler/GHC/Core/Subst.hs b/compiler/GHC/Core/Subst.hs
index f0ad737fb6..e6fd91dc0a 100644
--- a/compiler/GHC/Core/Subst.hs
+++ b/compiler/GHC/Core/Subst.hs
@@ -417,11 +417,12 @@ cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
 cloneIdBndrs subst us ids
   = mapAccumL (clone_id subst) subst (ids `zip` uniqsFromSupply us)
 
-cloneBndrs :: Subst -> UniqSupply -> [Var] -> (Subst, [Var])
+cloneBndrs :: MonadUnique m => Subst -> [Var] -> m (Subst, [Var])
 -- Works for all kinds of variables (typically case binders)
 -- not just Ids
-cloneBndrs subst us vs
-  = mapAccumL (\subst (v, u) -> cloneBndr subst u v) subst (vs `zip` uniqsFromSupply us)
+cloneBndrs subst vs
+  = do us <- getUniquesM
+       pure $ mapAccumL (\subst (v, u) -> cloneBndr subst u v) subst (vs `zip` us)
 
 cloneBndr :: Subst -> Unique -> Var -> (Subst, Var)
 cloneBndr subst uniq v
@@ -429,12 +430,11 @@ cloneBndr subst uniq v
   | otherwise = clone_id subst subst (v,uniq)  -- Works for coercion variables too
 
 -- | Clone a mutually recursive group of 'Id's
-cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
-cloneRecIdBndrs subst us ids
-  = (subst', ids')
-  where
-    (subst', ids') = mapAccumL (clone_id subst') subst
-                               (ids `zip` uniqsFromSupply us)
+cloneRecIdBndrs :: MonadUnique m => Subst -> [Id] -> m (Subst, [Id])
+cloneRecIdBndrs subst ids
+  = do us <- getUniquesM
+       let (subst', ids') = mapAccumL (clone_id subst') subst (ids `zip` us)
+       pure (subst', ids')
 
 -- Just like substIdBndr, except that it always makes a new unique
 -- It is given the unique to use
diff --git a/compiler/GHC/StgToJS/Linker/Utils.hs b/compiler/GHC/StgToJS/Linker/Utils.hs
index 36a190fed6..539bc8e593 100644
--- a/compiler/GHC/StgToJS/Linker/Utils.hs
+++ b/compiler/GHC/StgToJS/Linker/Utils.hs
@@ -41,6 +41,7 @@ import          GHC.StgToJS.Types
 
 import           Prelude
 import GHC.Platform
+import GHC.Utils.Misc
 import Data.List (isPrefixOf)
 import System.IO
 import Data.Char (isSpace)
@@ -299,7 +300,7 @@ getJsOptions handle = do
 parseJsOptions :: String -> [JSOption]
 parseJsOptions xs = go xs
   where
-    trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace
+    trim = dropWhileEndLE isSpace . dropWhile isSpace
     go [] = []
     go xs = let (tok, rest) = break (== ',') xs
                 tok' = trim tok
diff --git a/libraries/base/GHC/Event/Manager.hs b/libraries/base/GHC/Event/Manager.hs
index 88bf450426..bdc2c3616a 100644
--- a/libraries/base/GHC/Event/Manager.hs
+++ b/libraries/base/GHC/Event/Manager.hs
@@ -467,7 +467,7 @@ onFdEvent mgr fd evs
         IT.delete (fromIntegral fd) tbl >>= maybe (return []) (selectCallbacks tbl)
     forM_ fdds $ \(FdData reg _ cb) -> cb reg evs
   where
-    -- | Here we look through the list of registrations for the fd of interest
+    -- Here we look through the list of registrations for the fd of interest
     -- and sort out which match the events that were triggered. We,
     --
     --   1. re-arm the fd as appropriate
diff --git a/libraries/base/GHC/Event/TimerManager.hs b/libraries/base/GHC/Event/TimerManager.hs
index b334924a9d..2d68f65902 100644
--- a/libraries/base/GHC/Event/TimerManager.hs
+++ b/libraries/base/GHC/Event/TimerManager.hs
@@ -175,7 +175,7 @@ step mgr = do
   state `seq` return (state == Running)
  where
 
-  -- | Call all expired timer callbacks and return the time to the
+  -- Call all expired timer callbacks and return the time to the
   -- next timeout.
   mkTimeout :: IO Timeout
   mkTimeout = do
diff --git a/libraries/base/GHC/Fingerprint.hs b/libraries/base/GHC/Fingerprint.hs
index cb5e3456c9..5b803d8a74 100644
--- a/libraries/base/GHC/Fingerprint.hs
+++ b/libraries/base/GHC/Fingerprint.hs
@@ -84,7 +84,7 @@ getFileHash path = withBinaryFile path ReadMode $ \h ->
   where
     _BUFSIZE = 4096
 
-    -- | Loop over _BUFSIZE sized chunks read from the handle,
+    -- Loop over _BUFSIZE sized chunks read from the handle,
     -- passing the callback a block of bytes and its size.
     processChunks :: Handle -> (Ptr Word8 -> Int -> IO ()) -> IO ()
     processChunks h f = allocaBytes _BUFSIZE $ \arrPtr ->
diff --git a/libraries/base/GHC/Fingerprint/Type.hs b/libraries/base/GHC/Fingerprint/Type.hs
index 234bac1d43..15e9d73983 100644
--- a/libraries/base/GHC/Fingerprint/Type.hs
+++ b/libraries/base/GHC/Fingerprint/Type.hs
@@ -30,7 +30,7 @@ data Fingerprint = Fingerprint {-# UNPACK #-} !Word64 {-# UNPACK #-} !Word64
 instance Show Fingerprint where
   show (Fingerprint w1 w2) = hex16 w1 ++ hex16 w2
     where
-      -- | Formats a 64 bit number as 16 digits hex.
+      -- Formats a 64 bit number as 16 digits hex.
       hex16 :: Word64 -> String
       hex16 i = let hex = showHex i ""
                  in replicate (16 - length hex) '0' ++ hex
diff --git a/libraries/base/GHC/IO/Encoding/Types.hs b/libraries/base/GHC/IO/Encoding/Types.hs
index 2f8ffd5e59..d0ee5a3124 100644
--- a/libraries/base/GHC/IO/Encoding/Types.hs
+++ b/libraries/base/GHC/IO/Encoding/Types.hs
@@ -119,7 +119,6 @@ data TextEncoding
 
 -- | @since 4.3.0.0
 instance Show TextEncoding where
-  -- | Returns the value of 'textEncodingName'
   show te = textEncodingName te
 
 -- | @since 4.4.0.0
diff --git a/utils/deriveConstants/Main.hs b/utils/deriveConstants/Main.hs
index f1d1cd742c..c51f14382c 100644
--- a/utils/deriveConstants/Main.hs
+++ b/utils/deriveConstants/Main.hs
@@ -27,7 +27,6 @@ needing to run the program, by inspecting the object file using 'nm'.
 
 import Control.Monad (when, unless)
 import Data.Bits (shiftL)
-import Data.Char (toLower)
 import Data.List (elemIndex, stripPrefix, intercalate)
 import Data.Map (Map)
 import qualified Data.Map as Map