Scrub some no-warning pragmas.

59 files changed, 143 insertions, 270 deletions

diff --git a/compiler/GHC/Builtin/Types.hs b/compiler/GHC/Builtin/Types.hs
index 5e59c30884..9e1780d475 100644
--- a/compiler/GHC/Builtin/Types.hs
+++ b/compiler/GHC/Builtin/Types.hs
@@ -207,6 +207,7 @@ import GHC.Utils.Panic.Plain
 
 import qualified Data.ByteString.Char8 as BS
 
+import Data.Foldable
 import Data.List        ( elemIndex, intersperse )
 
 alpha_tyvar :: [TyVar]
@@ -1611,7 +1612,7 @@ sumRepDataCon = pcSpecialDataCon sumRepDataConName [ mkListTy runtimeRepTy ]
   where
     -- See Note [Getting from RuntimeRep to PrimRep] in GHC.Types.RepType
     prim_rep_fun [rr_ty_list]
-      = map slotPrimRep (ubxSumRepType prim_repss)
+      = map slotPrimRep (toList (ubxSumRepType prim_repss))
       where
         rr_tys     = extractPromotedList rr_ty_list
         doc        = text "sumRepDataCon" <+> ppr rr_tys
@@ -1734,27 +1735,9 @@ unliftedRepTy = mkTyConTy unliftedRepTyCon
 vecCountTyConName :: Name
 vecCountTyConName = mkWiredInTyConName UserSyntax gHC_TYPES (fsLit "VecCount") vecCountTyConKey vecCountTyCon
 
--- See Note [Wiring in RuntimeRep]
-vecCountDataConNames :: [Name]
-vecCountDataConNames = zipWith3Lazy mk_runtime_rep_dc_name
-                         [ fsLit "Vec2", fsLit "Vec4", fsLit "Vec8"
-                         , fsLit "Vec16", fsLit "Vec32", fsLit "Vec64" ]
-                         vecCountDataConKeys
-                         vecCountDataCons
-
 vecElemTyConName :: Name
 vecElemTyConName = mkWiredInTyConName UserSyntax gHC_TYPES (fsLit "VecElem") vecElemTyConKey vecElemTyCon
 
--- See Note [Wiring in RuntimeRep]
-vecElemDataConNames :: [Name]
-vecElemDataConNames = zipWith3Lazy mk_runtime_rep_dc_name
-                        [ fsLit "Int8ElemRep", fsLit "Int16ElemRep", fsLit "Int32ElemRep"
-                        , fsLit "Int64ElemRep", fsLit "Word8ElemRep", fsLit "Word16ElemRep"
-                        , fsLit "Word32ElemRep", fsLit "Word64ElemRep"
-                        , fsLit "FloatElemRep", fsLit "DoubleElemRep" ]
-                        vecElemDataConKeys
-                        vecElemDataCons
-
 vecRepDataCon :: DataCon
 vecRepDataCon = pcSpecialDataCon vecRepDataConName [ mkTyConTy vecCountTyCon
                                                    , mkTyConTy vecElemTyCon ]
@@ -1777,12 +1760,13 @@ vecCountTyCon = pcTyCon vecCountTyConName Nothing [] vecCountDataCons
 
 -- See Note [Wiring in RuntimeRep]
 vecCountDataCons :: [DataCon]
-vecCountDataCons = zipWithLazy mk_vec_count_dc
-                     [ 2, 4, 8, 16, 32, 64 ]
-                     vecCountDataConNames
+vecCountDataCons = zipWith mk_vec_count_dc [1..6] vecCountDataConKeys
   where
-    mk_vec_count_dc n name
-      = pcSpecialDataCon name [] vecCountTyCon (VecCount n)
+    mk_vec_count_dc logN key = con
+      where
+        n = 2^(logN :: Int)
+        name = mk_runtime_rep_dc_name (fsLit ("Vec" ++ show n)) key con
+        con = pcSpecialDataCon name [] vecCountTyCon (VecCount n)
 
 -- See Note [Wiring in RuntimeRep]
 vec2DataConTy, vec4DataConTy, vec8DataConTy, vec16DataConTy, vec32DataConTy,
@@ -1795,14 +1779,19 @@ vecElemTyCon = pcTyCon vecElemTyConName Nothing [] vecElemDataCons
 
 -- See Note [Wiring in RuntimeRep]
 vecElemDataCons :: [DataCon]
-vecElemDataCons = zipWithLazy mk_vec_elem_dc
-                    [ Int8ElemRep, Int16ElemRep, Int32ElemRep, Int64ElemRep
-                    , Word8ElemRep, Word16ElemRep, Word32ElemRep, Word64ElemRep
-                    , FloatElemRep, DoubleElemRep ]
-                    vecElemDataConNames
+vecElemDataCons = zipWith3 mk_vec_elem_dc
+  [ fsLit "Int8ElemRep", fsLit "Int16ElemRep", fsLit "Int32ElemRep", fsLit "Int64ElemRep"
+  , fsLit "Word8ElemRep", fsLit "Word16ElemRep", fsLit "Word32ElemRep", fsLit "Word64ElemRep"
+  , fsLit "FloatElemRep", fsLit "DoubleElemRep" ]
+  [ Int8ElemRep, Int16ElemRep, Int32ElemRep, Int64ElemRep
+  , Word8ElemRep, Word16ElemRep, Word32ElemRep, Word64ElemRep
+  , FloatElemRep, DoubleElemRep ]
+    vecElemDataConKeys
   where
-    mk_vec_elem_dc elem name
-      = pcSpecialDataCon name [] vecElemTyCon (VecElem elem)
+    mk_vec_elem_dc nameFs elemRep key = con
+      where
+        name = mk_runtime_rep_dc_name nameFs key con
+        con = pcSpecialDataCon name [] vecElemTyCon (VecElem elemRep)
 
 -- See Note [Wiring in RuntimeRep]
 int8ElemRepDataConTy, int16ElemRepDataConTy, int32ElemRepDataConTy,
diff --git a/compiler/GHC/Cmm/ContFlowOpt.hs b/compiler/GHC/Cmm/ContFlowOpt.hs
index 59ed1e760b..9fc364868a 100644
--- a/compiler/GHC/Cmm/ContFlowOpt.hs
+++ b/compiler/GHC/Cmm/ContFlowOpt.hs
@@ -1,6 +1,5 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE BangPatterns #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 module GHC.Cmm.ContFlowOpt
     ( cmmCfgOpts
     , cmmCfgOptsProc
diff --git a/compiler/GHC/Cmm/Node.hs b/compiler/GHC/Cmm/Node.hs
index 47930b2e99..0e381e31c4 100644
--- a/compiler/GHC/Cmm/Node.hs
+++ b/compiler/GHC/Cmm/Node.hs
@@ -9,9 +9,6 @@
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE LambdaCase #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 -- CmmNode type for representation using Hoopl graphs.
 
 module GHC.Cmm.Node (
@@ -33,6 +30,7 @@ import GHC.Cmm.CLabel
 import GHC.Cmm.Expr
 import GHC.Cmm.Switch
 import GHC.Data.FastString
+import GHC.Data.Pair
 import GHC.Types.ForeignCall
 import GHC.Utils.Outputable
 import GHC.Runtime.Heap.Layout
@@ -725,7 +723,7 @@ mapExpM _ (CmmComment _)            = Nothing
 mapExpM _ (CmmTick _)               = Nothing
 mapExpM f (CmmUnwind regs)          = CmmUnwind `fmap` mapM (\(r,e) -> mapM f e >>= \e' -> pure (r,e')) regs
 mapExpM f (CmmAssign r e)           = CmmAssign r `fmap` f e
-mapExpM f (CmmStore addr e align)   = (\[addr', e'] -> CmmStore addr' e' align) `fmap` mapListM f [addr, e]
+mapExpM f (CmmStore addr e align)   = (\ (Pair addr' e') -> CmmStore addr' e' align) `fmap` traverse f (Pair addr e)
 mapExpM _ (CmmBranch _)             = Nothing
 mapExpM f (CmmCondBranch e ti fi l) = (\x -> CmmCondBranch x ti fi l) `fmap` f e
 mapExpM f (CmmSwitch e tbl)         = (\x -> CmmSwitch x tbl)       `fmap` f e
diff --git a/compiler/GHC/Cmm/ProcPoint.hs b/compiler/GHC/Cmm/ProcPoint.hs
index ccf542aff0..7e6c542c5e 100644
--- a/compiler/GHC/Cmm/ProcPoint.hs
+++ b/compiler/GHC/Cmm/ProcPoint.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE DisambiguateRecordFields #-}
 {-# LANGUAGE GADTs #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Cmm.ProcPoint
     ( ProcPointSet, Status(..)
     , callProcPoints, minimalProcPointSet
diff --git a/compiler/GHC/CmmToAsm.hs b/compiler/GHC/CmmToAsm.hs
index d4da4dc51b..adb71e11a8 100644
--- a/compiler/GHC/CmmToAsm.hs
+++ b/compiler/GHC/CmmToAsm.hs
@@ -15,8 +15,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE UnboxedTuples #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Native code generator
 --
 -- The native-code generator has machine-independent and
diff --git a/compiler/GHC/Core.hs b/compiler/GHC/Core.hs
index 38d447b491..61fc14e815 100644
--- a/compiler/GHC/Core.hs
+++ b/compiler/GHC/Core.hs
@@ -7,9 +7,6 @@
 {-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE BangPatterns #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | GHC.Core holds all the main data types for use by for the Glasgow Haskell Compiler midsection
 module GHC.Core (
         -- * Main data types
diff --git a/compiler/GHC/Core/FamInstEnv.hs b/compiler/GHC/Core/FamInstEnv.hs
index 9bc4297af2..31d01d3893 100644
--- a/compiler/GHC/Core/FamInstEnv.hs
+++ b/compiler/GHC/Core/FamInstEnv.hs
@@ -3,7 +3,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections       #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 -- (c) The University of Glasgow 2006
 --
 -- FamInstEnv: Type checked family instance declarations
diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs
index df2a5c31c9..b12478cbab 100644
--- a/compiler/GHC/Core/Opt/Arity.hs
+++ b/compiler/GHC/Core/Opt/Arity.hs
@@ -7,7 +7,6 @@
 -}
 
 {-# LANGUAGE CPP #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 -- | Arity and eta expansion
 module GHC.Core.Opt.Arity
diff --git a/compiler/GHC/Core/Opt/CSE.hs b/compiler/GHC/Core/Opt/CSE.hs
index f8a129de85..2f7718709a 100644
--- a/compiler/GHC/Core/Opt/CSE.hs
+++ b/compiler/GHC/Core/Opt/CSE.hs
@@ -4,11 +4,6 @@
 \section{Common subexpression}
 -}
 
-
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Core.Opt.CSE (cseProgram, cseOneExpr) where
 
 import GHC.Prelude
@@ -32,6 +27,7 @@ import GHC.Types.Tickish
 import GHC.Core.Map.Expr
 import GHC.Utils.Misc   ( filterOut, equalLength )
 import GHC.Utils.Panic
+import Data.Functor.Identity ( Identity (..) )
 import Data.List        ( mapAccumL )
 
 {-
@@ -412,7 +408,7 @@ cseBind toplevel env (Rec [(in_id, rhs)])
   = (extendCSRecEnv env1 out_id rhs'' id_expr', Rec [(zapped_id, rhs')])
 
   where
-    (env1, [out_id]) = addRecBinders env [in_id]
+    (env1, Identity out_id) = addRecBinders env (Identity in_id)
     rhs'  = cseExpr env1 rhs
     rhs'' = stripTicksE tickishFloatable rhs'
     ticks = stripTicksT tickishFloatable rhs'
@@ -916,7 +912,8 @@ addBinders cse vs = (cse { cs_subst = sub' }, vs')
                 where
                   (sub', vs') = substBndrs (cs_subst cse) vs
 
-addRecBinders :: CSEnv -> [Id] -> (CSEnv, [Id])
-addRecBinders cse vs = (cse { cs_subst = sub' }, vs')
-                where
-                  (sub', vs') = substRecBndrs (cs_subst cse) vs
+addRecBinders :: Traversable f => CSEnv -> f Id -> (CSEnv, f Id)
+addRecBinders = \ cse vs ->
+    let (sub', vs') = substRecBndrs (cs_subst cse) vs
+    in (cse { cs_subst = sub' }, vs')
+{-# INLINE addRecBinders #-}
diff --git a/compiler/GHC/Core/Opt/Monad.hs b/compiler/GHC/Core/Opt/Monad.hs
index 0f87a8aeb6..6f520cfcfd 100644
--- a/compiler/GHC/Core/Opt/Monad.hs
+++ b/compiler/GHC/Core/Opt/Monad.hs
@@ -6,8 +6,6 @@
 
 {-# LANGUAGE DeriveFunctor #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Core.Opt.Monad (
     -- * Types used in core-to-core passes
     FloatOutSwitches(..),
diff --git a/compiler/GHC/Core/Opt/Simplify/Iteration.hs b/compiler/GHC/Core/Opt/Simplify/Iteration.hs
index f0e36f6fc9..f8ed00c119 100644
--- a/compiler/GHC/Core/Opt/Simplify/Iteration.hs
+++ b/compiler/GHC/Core/Opt/Simplify/Iteration.hs
@@ -8,7 +8,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE MultiWayIf #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates -Wno-incomplete-uni-patterns #-}
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 module GHC.Core.Opt.Simplify.Iteration ( simplTopBinds, simplExpr, simplImpRules ) where
 
 import GHC.Prelude
diff --git a/compiler/GHC/Core/Subst.hs b/compiler/GHC/Core/Subst.hs
index 4f87e5ad8e..3d52c655f6 100644
--- a/compiler/GHC/Core/Subst.hs
+++ b/compiler/GHC/Core/Subst.hs
@@ -6,8 +6,6 @@
 Utility functions on @Core@ syntax
 -}
 
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 module GHC.Core.Subst (
         -- * Main data types
         Subst(..), -- Implementation exported for supercompiler's Renaming.hs only
@@ -65,6 +63,7 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 
+import Data.Functor.Identity (Identity (..))
 import Data.List (mapAccumL)
 
 {-
@@ -343,15 +342,18 @@ substBndr subst bndr
   | otherwise     = substIdBndr (text "var-bndr") subst subst bndr
 
 -- | Applies 'substBndr' to a number of 'Var's, accumulating a new 'Subst' left-to-right
-substBndrs :: Subst -> [Var] -> (Subst, [Var])
-substBndrs subst bndrs = mapAccumL substBndr subst bndrs
+substBndrs :: Traversable f => Subst -> f Var -> (Subst, f Var)
+substBndrs = mapAccumL substBndr
+{-# INLINE substBndrs #-}
 
 -- | Substitute in a mutually recursive group of 'Id's
-substRecBndrs :: Subst -> [Id] -> (Subst, [Id])
+substRecBndrs :: Traversable f => Subst -> f Id -> (Subst, f Id)
 substRecBndrs subst bndrs
   = (new_subst, new_bndrs)
   where         -- Here's the reason we need to pass rec_subst to subst_id
     (new_subst, new_bndrs) = mapAccumL (substIdBndr (text "rec-bndr") new_subst) subst bndrs
+{-# SPECIALIZE substRecBndrs :: Subst -> [Id] -> (Subst, [Id]) #-}
+{-# SPECIALIZE substRecBndrs :: Subst -> Identity Id -> (Subst, Identity Id) #-}
 
 substIdBndr :: SDoc
             -> Subst            -- ^ Substitution to use for the IdInfo
diff --git a/compiler/GHC/Core/Tidy.hs b/compiler/GHC/Core/Tidy.hs
index 1ca425fcf2..2a4c538ab1 100644
--- a/compiler/GHC/Core/Tidy.hs
+++ b/compiler/GHC/Core/Tidy.hs
@@ -8,7 +8,6 @@ The code for *top-level* bindings is in GHC.Iface.Tidy.
 -}
 
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 module GHC.Core.Tidy (
         tidyExpr, tidyRules, tidyCbvInfoTop, tidyBndrs
     ) where
diff --git a/compiler/GHC/Core/TyCo/Subst.hs b/compiler/GHC/Core/TyCo/Subst.hs
index 115dd3531f..ebf87dae94 100644
--- a/compiler/GHC/Core/TyCo/Subst.hs
+++ b/compiler/GHC/Core/TyCo/Subst.hs
@@ -6,7 +6,6 @@ Type and Coercion - friends' interface
 
 
 {-# LANGUAGE BangPatterns #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 -- | Substitution into types and coercions.
 module GHC.Core.TyCo.Subst
diff --git a/compiler/GHC/Core/TyCo/Tidy.hs b/compiler/GHC/Core/TyCo/Tidy.hs
index a1f6489374..bfd7e4c7cc 100644
--- a/compiler/GHC/Core/TyCo/Tidy.hs
+++ b/compiler/GHC/Core/TyCo/Tidy.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE BangPatterns #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 
 -- | Tidying types and coercions for printing in error messages.
diff --git a/compiler/GHC/Core/Type.hs b/compiler/GHC/Core/Type.hs
index 70a707b17b..fdd5edbba2 100644
--- a/compiler/GHC/Core/Type.hs
+++ b/compiler/GHC/Core/Type.hs
@@ -5,7 +5,6 @@
 
 {-# LANGUAGE FlexibleContexts, PatternSynonyms, ViewPatterns, MultiWayIf #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 -- | Main functions for manipulating types and type-related things
 module GHC.Core.Type (
diff --git a/compiler/GHC/Driver/Make.hs b/compiler/GHC/Driver/Make.hs
index 462a52ea45..53d8040c9c 100644
--- a/compiler/GHC/Driver/Make.hs
+++ b/compiler/GHC/Driver/Make.hs
@@ -5,7 +5,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
diff --git a/compiler/GHC/Hs/Decls.hs b/compiler/GHC/Hs/Decls.hs
index d296f2b0a6..8e48036673 100644
--- a/compiler/GHC/Hs/Decls.hs
+++ b/compiler/GHC/Hs/Decls.hs
@@ -16,9 +16,6 @@
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
 
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Abstract syntax of global declarations.
 --
 -- Definitions for: @SynDecl@ and @ConDecl@, @ClassDecl@,
diff --git a/compiler/GHC/Hs/Expr.hs b/compiler/GHC/Hs/Expr.hs
index b24531f790..48cf7c6955 100644
--- a/compiler/GHC/Hs/Expr.hs
+++ b/compiler/GHC/Hs/Expr.hs
@@ -14,7 +14,6 @@
 {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
                                       -- in module Language.Haskell.Syntax.Extension
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 {-# OPTIONS_GHC -Wno-orphans #-} -- Outputable
 
 {-
diff --git a/compiler/GHC/HsToCore/Arrows.hs b/compiler/GHC/HsToCore/Arrows.hs
index a761440fc7..4794f11075 100644
--- a/compiler/GHC/HsToCore/Arrows.hs
+++ b/compiler/GHC/HsToCore/Arrows.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE BlockArguments #-}
 {-# LANGUAGE TupleSections #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/HsToCore/Binds.hs b/compiler/GHC/HsToCore/Binds.hs
index 7d1eeb3268..21cab8439d 100644
--- a/compiler/GHC/HsToCore/Binds.hs
+++ b/compiler/GHC/HsToCore/Binds.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -848,29 +846,52 @@ decomposeRuleLhs dflags orig_bndrs orig_lhs rhs_fvs
   , Just con <- isDataConId_maybe funId
   = Left (DsRuleIgnoredDueToConstructor con) -- See Note [No RULES on datacons]
 
-  | Nothing <- mb_lhs_app
-  = Left (DsRuleLhsTooComplicated orig_lhs lhs2)
-
-  | not (null unbound)    -- Check for things unbound on LHS
-                          -- See Note [Unused spec binders]
-  = -- pprTrace "decomposeRuleLhs 1" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
-    --                                     , text "orig_lhs:" <+> ppr orig_lhs
-    --                                     , text "lhs_fvs:" <+> ppr lhs_fvs
-    --                                     , text "rhs_fvs:" <+> ppr rhs_fvs
-    --                                     , text "unbound:" <+> ppr unbound
-    --                                     ]) $
-    Left (DsRuleBindersNotBound unbound orig_bndrs orig_lhs lhs2)
-
-  | otherwise
-  = -- pprTrace "decomposeRuleLhs 2" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
-    --                                    , text "orig_lhs:" <+> ppr orig_lhs
-    --                                    , text "lhs1:"     <+> ppr lhs1
-    --                                    , text "extra_bndrs:" <+> ppr extra_bndrs
-    --                                    , text "fn_id:" <+> ppr fn_id
-    --                                    , text "args:"   <+> ppr args
-    --                                    , text "args fvs:" <+> ppr (exprsFreeVarsList args)
-    --                                    ]) $
-    Right (trimmed_bndrs ++ extra_bndrs, fn_id, args)
+  | otherwise = case decompose fun2 args2 of
+        Nothing -> Left (DsRuleLhsTooComplicated orig_lhs lhs2)
+        Just (fn_id, args)
+          | not (null unbound) ->
+            -- Check for things unbound on LHS
+            -- See Note [Unused spec binders]
+            -- pprTrace "decomposeRuleLhs 1" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
+            --                                     , text "orig_lhs:" <+> ppr orig_lhs
+            --                                     , text "lhs_fvs:" <+> ppr lhs_fvs
+            --                                     , text "rhs_fvs:" <+> ppr rhs_fvs
+            --                                     , text "unbound:" <+> ppr unbound
+            --                                     ]) $
+            Left (DsRuleBindersNotBound unbound orig_bndrs orig_lhs lhs2)
+          | otherwise ->
+            -- pprTrace "decomposeRuleLhs 2" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
+            --                                    , text "orig_lhs:" <+> ppr orig_lhs
+            --                                    , text "lhs1:"     <+> ppr lhs1
+            --                                    , text "extra_bndrs:" <+> ppr extra_bndrs
+            --                                    , text "fn_id:" <+> ppr fn_id
+            --                                    , text "args:"   <+> ppr args
+            --                                    , text "args fvs:" <+> ppr (exprsFreeVarsList args)
+            --                                    ]) $
+            Right (trimmed_bndrs ++ extra_bndrs, fn_id, args)
+
+          where -- See Note [Variables unbound on the LHS]
+                lhs_fvs = exprsFreeVars args
+                all_fvs       = lhs_fvs `unionVarSet` rhs_fvs
+                trimmed_bndrs = filter (`elemVarSet` all_fvs) orig_bndrs
+                unbound       = filterOut (`elemVarSet` lhs_fvs) trimmed_bndrs
+                    -- Needed on RHS but not bound on LHS
+
+                -- Add extra tyvar binders: Note [Free tyvars on rule LHS]
+                -- and extra dict binders: Note [Free dictionaries on rule LHS]
+                extra_bndrs = scopedSort extra_tvs ++ extra_dicts
+                  where
+                    extra_tvs   = [ v | v <- extra_vars, isTyVar v ]
+                extra_dicts =
+                  [ mkLocalId (localiseName (idName d)) ManyTy (idType d)
+                  | d <- extra_vars, isDictId d ]
+                extra_vars  =
+                  [ v
+                  | v <- exprsFreeVarsList args
+                  , not (v `elemVarSet` orig_bndr_set)
+                  , not (v == fn_id) ]
+                    -- fn_id: do not quantify over the function itself, which may
+                    -- itself be a dictionary (in pathological cases, #10251)
 
  where
    simpl_opts    = initSimpleOpts dflags
@@ -880,29 +901,6 @@ decomposeRuleLhs dflags orig_bndrs orig_lhs rhs_fvs
    lhs2         = simpleOptExpr simpl_opts lhs1  -- See Note [Simplify rule LHS]
    (fun2,args2) = collectArgs lhs2
 
-   mb_lhs_app = decompose fun2 args2
-   Just (fn_id, args) = mb_lhs_app
-
-   -- See Note [Variables unbound on the LHS]
-   lhs_fvs       = exprsFreeVars args
-   all_fvs       = lhs_fvs `unionVarSet` rhs_fvs
-   trimmed_bndrs = filter (`elemVarSet` all_fvs) orig_bndrs
-   unbound       = filterOut (`elemVarSet` lhs_fvs) trimmed_bndrs
-                   -- Needed on RHS but not bound on LHS
-
-        -- Add extra tyvar binders: Note [Free tyvars on rule LHS]
-        -- and extra dict binders: Note [Free dictionaries on rule LHS]
-   extra_bndrs = scopedSort extra_tvs ++ extra_dicts
-     where
-       extra_tvs   = [ v | v <- extra_vars, isTyVar v ]
-       extra_dicts = [ mkLocalId (localiseName (idName d)) ManyTy (idType d)
-                     | d <- extra_vars, isDictId d ]
-       extra_vars  = [ v | v <- exprsFreeVarsList args
-                         , not (v `elemVarSet` orig_bndr_set)
-                         , not (v == fn_id) ]
-         -- fn_id: do not quantify over the function itself, which may
-         -- itself be a dictionary (in pathological cases, #10251)
-
    decompose (Var fn_id) args
       | not (fn_id `elemVarSet` orig_bndr_set)
       = Just (fn_id, args)
@@ -1253,8 +1251,7 @@ dsEvTypeable :: Type -> EvTypeable -> DsM CoreExpr
 dsEvTypeable ty ev
   = do { tyCl <- dsLookupTyCon typeableClassName    -- Typeable
        ; let kind = typeKind ty
-             Just typeable_data_con
-                 = tyConSingleDataCon_maybe tyCl    -- "Data constructor"
+             typeable_data_con = tyConSingleDataCon tyCl  -- "Data constructor"
                                                     -- for Typeable
 
        ; rep_expr <- ds_ev_typeable ty ev           -- :: TypeRep a
diff --git a/compiler/GHC/HsToCore/Expr.hs b/compiler/GHC/HsToCore/Expr.hs
index 9f81f6b0b3..92ab68c5b8 100644
--- a/compiler/GHC/HsToCore/Expr.hs
+++ b/compiler/GHC/HsToCore/Expr.hs
@@ -3,7 +3,6 @@
 {-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/HsToCore/Foreign/Decl.hs b/compiler/GHC/HsToCore/Foreign/Decl.hs
index 8257fea3bb..89be7cca40 100644
--- a/compiler/GHC/HsToCore/Foreign/Decl.hs
+++ b/compiler/GHC/HsToCore/Foreign/Decl.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The AQUA Project, Glasgow University, 1998
diff --git a/compiler/GHC/HsToCore/Match.hs b/compiler/GHC/HsToCore/Match.hs
index cc9d282356..0cf83d378c 100644
--- a/compiler/GHC/HsToCore/Match.hs
+++ b/compiler/GHC/HsToCore/Match.hs
@@ -6,7 +6,6 @@
 {-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/Iface/Rename.hs b/compiler/GHC/Iface/Rename.hs
index 9c3716fe97..a14b3959ea 100644
--- a/compiler/GHC/Iface/Rename.hs
+++ b/compiler/GHC/Iface/Rename.hs
@@ -1,7 +1,3 @@
-
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | This module implements interface renaming, which is
 -- used to rewrite interface files on the fly when we
 -- are doing indefinite typechecking and need instantiations
diff --git a/compiler/GHC/Parser/PostProcess.hs b/compiler/GHC/Parser/PostProcess.hs
index 02ef74efef..e957c600e1 100644
--- a/compiler/GHC/Parser/PostProcess.hs
+++ b/compiler/GHC/Parser/PostProcess.hs
@@ -10,8 +10,6 @@
 {-# LANGUAGE ViewPatterns #-}
 {-# LANGUAGE DataKinds #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 --
 --  (c) The University of Glasgow 2002-2006
 --
diff --git a/compiler/GHC/Rename/Bind.hs b/compiler/GHC/Rename/Bind.hs
index 7f3edf841c..349fc770b6 100644
--- a/compiler/GHC/Rename/Bind.hs
+++ b/compiler/GHC/Rename/Bind.hs
@@ -3,7 +3,6 @@
 {-# LANGUAGE TypeFamilies #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/Rename/Expr.hs b/compiler/GHC/Rename/Expr.hs
index 4d22a994e9..ba39a2040c 100644
--- a/compiler/GHC/Rename/Expr.hs
+++ b/compiler/GHC/Rename/Expr.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeApplications    #-}
 {-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE ViewPatterns        #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
@@ -77,7 +78,7 @@ import qualified GHC.LanguageExtensions as LangExt
 import Language.Haskell.Syntax.Basic (FieldLabelString(..))
 
 import Data.List (unzip4, minimumBy)
-import Data.List.NonEmpty ( NonEmpty(..) )
+import Data.List.NonEmpty ( NonEmpty(..), nonEmpty )
 import Data.Maybe (isJust, isNothing)
 import Control.Arrow (first)
 import Data.Ord
@@ -1089,15 +1090,13 @@ rnStmtsWithFreeVars ctxt _ [] thing_inside
        ; (thing, fvs) <- thing_inside []
        ; return (([], thing), fvs) }
 
-rnStmtsWithFreeVars mDoExpr@(HsDoStmt MDoExpr{}) rnBody stmts thing_inside    -- Deal with mdo
+rnStmtsWithFreeVars mDoExpr@(HsDoStmt MDoExpr{}) rnBody (nonEmpty -> Just stmts) thing_inside    -- Deal with mdo
   = -- Behave like do { rec { ...all but last... }; last }
     do { ((stmts1, (stmts2, thing)), fvs)
-           <- rnStmt mDoExpr rnBody (noLocA $ mkRecStmt noAnn (noLocA all_but_last)) $ \ _ ->
-              do { last_stmt' <- checkLastStmt mDoExpr last_stmt
+           <- rnStmt mDoExpr rnBody (noLocA $ mkRecStmt noAnn (noLocA (NE.init stmts))) $ \ _ ->
+              do { last_stmt' <- checkLastStmt mDoExpr (NE.last stmts)
                  ; rnStmt mDoExpr rnBody last_stmt' thing_inside }
         ; return (((stmts1 ++ stmts2), thing), fvs) }
-  where
-    Just (all_but_last, last_stmt) = snocView stmts
 
 rnStmtsWithFreeVars ctxt rnBody (lstmt@(L loc _) : lstmts) thing_inside
   | null lstmts
diff --git a/compiler/GHC/Rename/Module.hs b/compiler/GHC/Rename/Module.hs
index 74058503ca..b0bb1cbd68 100644
--- a/compiler/GHC/Rename/Module.hs
+++ b/compiler/GHC/Rename/Module.hs
@@ -4,7 +4,6 @@
 {-# LANGUAGE TypeFamilies        #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/Rename/Names.hs b/compiler/GHC/Rename/Names.hs
index da2d5b0d57..c4cb5d8d01 100644
--- a/compiler/GHC/Rename/Names.hs
+++ b/compiler/GHC/Rename/Names.hs
@@ -11,9 +11,6 @@ Extracting imported and top-level names in scope
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE LambdaCase #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Rename.Names (
         rnImports, getLocalNonValBinders, newRecordSelector,
         extendGlobalRdrEnvRn,
@@ -919,8 +916,15 @@ getLocalNonValBinders fixity_env
           --    foreign decls and pattern synonyms for an ordinary module
           --    type sigs in case of a hs-boot file only
         ; is_boot <- tcIsHsBootOrSig
-        ; let val_bndrs | is_boot   = hs_boot_sig_bndrs
-                        | otherwise = for_hs_bndrs
+        ; let val_bndrs
+                | is_boot = case binds of
+                      ValBinds _ _val_binds val_sigs ->
+                          -- In a hs-boot file, the value binders come from the
+                          --  *signatures*, and there should be no foreign binders
+                          [ L (l2l decl_loc) (unLoc n)
+                          | L decl_loc (TypeSig _ ns _) <- val_sigs, n <- ns]
+                      _ -> panic "Non-ValBinds in hs-boot group"
+                | otherwise = for_hs_bndrs
         ; val_avails <- mapM new_simple val_bndrs
 
         ; let avails    = concat nti_availss ++ val_avails
@@ -941,16 +945,9 @@ getLocalNonValBinders fixity_env
         ; traceRn "getLocalNonValBinders 3" (vcat [ppr flds, ppr field_env])
         ; return (envs, new_bndrs) } }
   where
-    ValBinds _ _val_binds val_sigs = binds
-
     for_hs_bndrs :: [LocatedN RdrName]
     for_hs_bndrs = hsForeignDeclsBinders foreign_decls
 
-    -- In a hs-boot file, the value binders come from the
-    --  *signatures*, and there should be no foreign binders
-    hs_boot_sig_bndrs = [ L (l2l decl_loc) (unLoc n)
-                        | L decl_loc (TypeSig _ ns _) <- val_sigs, n <- ns]
-
       -- the SrcSpan attached to the input should be the span of the
       -- declaration, not just the name
     new_simple :: LocatedN RdrName -> RnM AvailInfo
diff --git a/compiler/GHC/Rename/Pat.hs b/compiler/GHC/Rename/Pat.hs
index 7d8b54fa95..c73b1edcad 100644
--- a/compiler/GHC/Rename/Pat.hs
+++ b/compiler/GHC/Rename/Pat.hs
@@ -7,9 +7,6 @@
 {-# LANGUAGE ViewPatterns        #-}
 {-# LANGUAGE DisambiguateRecordFields #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -78,6 +75,8 @@ import GHC.Driver.Session ( getDynFlags, xopt_DuplicateRecordFields )
 import qualified GHC.LanguageExtensions as LangExt
 
 import Control.Monad       ( when, ap, guard, unless )
+import Data.Foldable
+import Data.Functor.Identity ( Identity (..) )
 import qualified Data.List.NonEmpty as NE
 import Data.Maybe
 import Data.Ratio
@@ -405,9 +404,10 @@ There are various entry points to renaming patterns, depending on
 --   * local namemaker
 --   * unused and duplicate checking
 --   * no fixities
-rnPats :: HsMatchContext GhcRn -- for error messages
-       -> [LPat GhcPs]
-       -> ([LPat GhcRn] -> RnM (a, FreeVars))
+rnPats :: Traversable f
+       => HsMatchContext GhcRn -- for error messages
+       -> f (LPat GhcPs)
+       -> (f (LPat GhcRn) -> RnM (a, FreeVars))
        -> RnM (a, FreeVars)
 rnPats ctxt pats thing_inside
   = do  { envs_before <- getRdrEnvs
@@ -424,7 +424,7 @@ rnPats ctxt pats thing_inside
           --    complain *twice* about duplicates e.g. f (x,x) = ...
           --
           -- See Note [Don't report shadowing for pattern synonyms]
-        ; let bndrs = collectPatsBinders CollNoDictBinders pats'
+        ; let bndrs = collectPatsBinders CollNoDictBinders (toList pats')
         ; addErrCtxt doc_pat $
           if isPatSynCtxt ctxt
              then checkDupNames bndrs
@@ -432,6 +432,8 @@ rnPats ctxt pats thing_inside
         ; thing_inside pats' } }
   where
     doc_pat = text "In" <+> pprMatchContext ctxt
+{-# SPECIALIZE rnPats :: HsMatchContext GhcRn -> [LPat GhcPs] -> ([LPat GhcRn] -> RnM (a, FreeVars)) -> RnM (a, FreeVars) #-}
+{-# SPECIALIZE rnPats :: HsMatchContext GhcRn -> Identity (LPat GhcPs) -> (Identity (LPat GhcRn) -> RnM (a, FreeVars)) -> RnM (a, FreeVars) #-}
 
 rnPat :: HsMatchContext GhcRn -- for error messages
       -> LPat GhcPs
@@ -439,7 +441,7 @@ rnPat :: HsMatchContext GhcRn -- for error messages
       -> RnM (a, FreeVars)     -- Variables bound by pattern do not
                                -- appear in the result FreeVars
 rnPat ctxt pat thing_inside
-  = rnPats ctxt [pat] (\pats' -> let [pat'] = pats' in thing_inside pat')
+  = rnPats ctxt (Identity pat) (thing_inside . runIdentity)
 
 applyNameMaker :: NameMaker -> LocatedN RdrName -> RnM (LocatedN Name)
 applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newPatLName mk rdr)
@@ -471,7 +473,7 @@ rnBindPat name_maker pat = runCps (rnLPatAndThen name_maker pat)
 -- ----------- Entry point 3: rnLPatAndThen -------------------
 -- General version: parameterized by how you make new names
 
-rnLPatsAndThen :: NameMaker -> [LPat GhcPs] -> CpsRn [LPat GhcRn]
+rnLPatsAndThen :: Traversable f => NameMaker -> f (LPat GhcPs) -> CpsRn (f (LPat GhcRn))
 rnLPatsAndThen mk = mapM (rnLPatAndThen mk)
   -- Despite the map, the monad ensures that each pattern binds
   -- variables that may be mentioned in subsequent patterns in the list
@@ -963,7 +965,7 @@ generalizeOverLitVal (HsFractional fl@(FL {fl_text=src,fl_neg=neg,fl_exp=e}))
     , denominator val == 1 = HsIntegral (IL {il_text=src,il_neg=neg,il_value=numerator val})
 generalizeOverLitVal lit = lit
 
-isNegativeZeroOverLit :: HsOverLit t -> Bool
+isNegativeZeroOverLit :: (XXOverLit t ~ DataConCantHappen) => HsOverLit t -> Bool
 isNegativeZeroOverLit lit
  = case ol_val lit of
         HsIntegral i    -> 0 == il_value i && il_neg i
@@ -985,7 +987,7 @@ in this case return not only literal itself but also negateName so that users
 can apply it explicitly. In this case it stays negative zero.  #13211
 -}
 
-rnOverLit :: HsOverLit t ->
+rnOverLit :: (XXOverLit t ~ DataConCantHappen) => HsOverLit t ->
              RnM ((HsOverLit GhcRn, Maybe (HsExpr GhcRn)), FreeVars)
 rnOverLit origLit
   = do  { opt_NumDecimals <- xoptM LangExt.NumDecimals
diff --git a/compiler/GHC/Rename/Splice.hs b/compiler/GHC/Rename/Splice.hs
index 1d84d794ae..e657141358 100644
--- a/compiler/GHC/Rename/Splice.hs
+++ b/compiler/GHC/Rename/Splice.hs
@@ -1,8 +1,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Rename.Splice (
         rnTopSpliceDecls,
 
diff --git a/compiler/GHC/Rename/Utils.hs b/compiler/GHC/Rename/Utils.hs
index fcf6b21b7a..66d96b163b 100644
--- a/compiler/GHC/Rename/Utils.hs
+++ b/compiler/GHC/Rename/Utils.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies     #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 {-
 
 This module contains miscellaneous functions related to renaming.
diff --git a/compiler/GHC/Stg/Unarise.hs b/compiler/GHC/Stg/Unarise.hs
index 432c13fdf4..35eb37b17f 100644
--- a/compiler/GHC/Stg/Unarise.hs
+++ b/compiler/GHC/Stg/Unarise.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TupleSections    #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-2012
 
@@ -279,6 +277,7 @@ import GHC.Utils.Misc
 import GHC.Types.Var.Env
 
 import Data.Bifunctor (second)
+import Data.List.NonEmpty (NonEmpty (..))
 import Data.Maybe (mapMaybe)
 import qualified Data.IntMap as IM
 
@@ -483,10 +482,9 @@ elimCase rho args bndr (MultiValAlt _) [GenStgAlt{ alt_con   = _
 
        unariseExpr rho2 rhs
 
-elimCase rho args bndr (MultiValAlt _) alts
+elimCase rho args@(tag_arg : real_args) bndr (MultiValAlt _) alts
   | isUnboxedSumBndr bndr
-  = do let (tag_arg : real_args) = args
-       tag_bndr <- mkId (mkFastString "tag") tagTy
+  = do tag_bndr <- mkId (mkFastString "tag") tagTy
           -- this won't be used but we need a binder anyway
        let rho1 = extendRho rho bndr (MultiVal args)
            scrut' = case tag_arg of
@@ -658,7 +656,7 @@ mkUbxSum
   -> [OutStgArg]  -- Final tuple arguments
 mkUbxSum dc ty_args args0
   = let
-      (_ : sum_slots) = ubxSumRepType (map typePrimRep ty_args)
+      _ :| sum_slots = ubxSumRepType (map typePrimRep ty_args)
         -- drop tag slot
 
       tag = dataConTag dc
diff --git a/compiler/GHC/StgToByteCode.hs b/compiler/GHC/StgToByteCode.hs
index bcf0990b49..989121207d 100644
--- a/compiler/GHC/StgToByteCode.hs
+++ b/compiler/GHC/StgToByteCode.hs
@@ -5,7 +5,6 @@
 {-# LANGUAGE FlexibleContexts           #-}
 
 {-# OPTIONS_GHC -fprof-auto-top #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
 --
 --  (c) The University of Glasgow 2002-2006
diff --git a/compiler/GHC/StgToCmm/Heap.hs b/compiler/GHC/StgToCmm/Heap.hs
index 9e493dff3e..55132860d6 100644
--- a/compiler/GHC/StgToCmm/Heap.hs
+++ b/compiler/GHC/StgToCmm/Heap.hs
@@ -6,8 +6,6 @@
 --
 -----------------------------------------------------------------------------
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.StgToCmm.Heap (
         getVirtHp, setVirtHp, setRealHp,
         getHpRelOffset,
@@ -612,10 +610,6 @@ do_checks mb_stk_hwm checkYield mb_alloc_lit do_gc = do
   gc_id       <- newBlockId
 
   let
-    Just alloc_lit = mb_alloc_lit
-
-    bump_hp   = cmmOffsetExprB platform hpExpr alloc_lit
-
     -- Sp overflow if ((old + 0) - CmmHighStack < SpLim)
     -- At the beginning of a function old + 0 = Sp
     -- See Note [Single stack check]
@@ -630,8 +624,6 @@ do_checks mb_stk_hwm checkYield mb_alloc_lit do_gc = do
     -- HpLim points to the LAST WORD of valid allocation space.
     hp_oflo = CmmMachOp (mo_wordUGt platform) [hpExpr, hpLimExpr]
 
-    alloc_n = mkAssign hpAllocReg alloc_lit
-
   case mb_stk_hwm of
     Nothing -> return ()
     Just stk_hwm -> tickyStackCheck
@@ -646,12 +638,14 @@ do_checks mb_stk_hwm checkYield mb_alloc_lit do_gc = do
         | checkYield && isJust mb_stk_hwm -> emitLabel loop_header_id
     _otherwise -> return ()
 
-  if isJust mb_alloc_lit
-    then do
+  case mb_alloc_lit of
+    Just alloc_lit -> do
+     let bump_hp   = cmmOffsetExprB platform hpExpr alloc_lit
+         alloc_n = mkAssign hpAllocReg alloc_lit
      tickyHeapCheck
      emitAssign hpReg bump_hp
      emit =<< mkCmmIfThen' hp_oflo (alloc_n <*> mkBranch gc_id) (Just False)
-    else
+    Nothing ->
       when (checkYield && not omit_yields) $ do
          -- Yielding if HpLim == 0
          let yielding = CmmMachOp (mo_wordEq platform)
diff --git a/compiler/GHC/Tc/Errors/Hole.hs b/compiler/GHC/Tc/Errors/Hole.hs
index c2181e5c32..d4ee8abef2 100644
--- a/compiler/GHC/Tc/Errors/Hole.hs
+++ b/compiler/GHC/Tc/Errors/Hole.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE ExistentialQuantification #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Tc.Errors.Hole
    ( findValidHoleFits
    , tcCheckHoleFit
diff --git a/compiler/GHC/Tc/Gen/App.hs b/compiler/GHC/Tc/Gen/App.hs
index c44fb65a29..06158cace3 100644
--- a/compiler/GHC/Tc/Gen/App.hs
+++ b/compiler/GHC/Tc/Gen/App.hs
@@ -6,8 +6,6 @@
 {-# LANGUAGE TypeFamilies        #-}
 {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 {-
 %
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/Tc/Gen/Head.hs b/compiler/GHC/Tc/Gen/Head.hs
index 99b09487b1..5154d7c98a 100644
--- a/compiler/GHC/Tc/Gen/Head.hs
+++ b/compiler/GHC/Tc/Gen/Head.hs
@@ -9,8 +9,6 @@
 {-# LANGUAGE ViewPatterns        #-}
 {-# LANGUAGE DisambiguateRecordFields #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 {-
 %
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/Tc/Solver/Interact.hs b/compiler/GHC/Tc/Solver/Interact.hs
index 8db260182d..139bb3b6b8 100644
--- a/compiler/GHC/Tc/Solver/Interact.hs
+++ b/compiler/GHC/Tc/Solver/Interact.hs
@@ -1,4 +1,3 @@
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 
 module GHC.Tc.Solver.Interact (
diff --git a/compiler/GHC/Tc/Solver/Monad.hs b/compiler/GHC/Tc/Solver/Monad.hs
index 63f8216633..12b6fcc69f 100644
--- a/compiler/GHC/Tc/Solver/Monad.hs
+++ b/compiler/GHC/Tc/Solver/Monad.hs
@@ -8,7 +8,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE ViewPatterns #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates -Wno-orphans #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
 
 -- | Monadic definitions for the constraint solver
 module GHC.Tc.Solver.Monad (
diff --git a/compiler/GHC/Tc/Solver/Rewrite.hs b/compiler/GHC/Tc/Solver/Rewrite.hs
index 33b25f29a7..252e2aba52 100644
--- a/compiler/GHC/Tc/Solver/Rewrite.hs
+++ b/compiler/GHC/Tc/Solver/Rewrite.hs
@@ -2,8 +2,6 @@
 
 {-# LANGUAGE DeriveFunctor #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Tc.Solver.Rewrite(
    rewrite, rewriteArgsNom,
    rewriteType
diff --git a/compiler/GHC/Tc/Solver/Types.hs b/compiler/GHC/Tc/Solver/Types.hs
index d7a46a7c61..4c52721638 100644
--- a/compiler/GHC/Tc/Solver/Types.hs
+++ b/compiler/GHC/Tc/Solver/Types.hs
@@ -1,8 +1,6 @@
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE GADTs #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Utility types used within the constraint solver
 module GHC.Tc.Solver.Types (
     -- Inert CDictCans
diff --git a/compiler/GHC/Tc/TyCl/Instance.hs b/compiler/GHC/Tc/TyCl/Instance.hs
index 06a06a0fad..6fda868642 100644
--- a/compiler/GHC/Tc/TyCl/Instance.hs
+++ b/compiler/GHC/Tc/TyCl/Instance.hs
@@ -8,7 +8,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 -- | Typechecking instance declarations
@@ -1284,7 +1283,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds })
        ; self_dict <- newDict clas inst_tys
        ; let class_tc      = classTyCon clas
              loc'          = noAnnSrcSpan loc
-             [dict_constr] = tyConDataCons class_tc
+             dict_constr   = tyConSingleDataCon class_tc
              dict_bind = mkVarBind self_dict (L loc' con_app_args)
 
                      -- We don't produce a binding for the dict_constr; instead we
@@ -1368,7 +1367,7 @@ addDFunPrags dfun_id sc_meth_ids
    ev_ids      = mkTemplateLocalsNum 1                    dfun_theta
    dfun_bndrs  = dfun_tvs ++ ev_ids
    clas_tc     = classTyCon clas
-   [dict_con]  = tyConDataCons clas_tc
+   dict_con    = tyConSingleDataCon clas_tc
    is_newtype  = isNewTyCon clas_tc
 
 wrapId :: HsWrapper -> Id -> HsExpr GhcTc
diff --git a/compiler/GHC/Tc/TyCl/PatSyn.hs b/compiler/GHC/Tc/TyCl/PatSyn.hs
index fdc4e59f1e..4c691185aa 100644
--- a/compiler/GHC/Tc/TyCl/PatSyn.hs
+++ b/compiler/GHC/Tc/TyCl/PatSyn.hs
@@ -2,8 +2,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/Tc/Types/Constraint.hs b/compiler/GHC/Tc/Types/Constraint.hs
index 572efd34d4..475437701c 100644
--- a/compiler/GHC/Tc/Types/Constraint.hs
+++ b/compiler/GHC/Tc/Types/Constraint.hs
@@ -3,8 +3,6 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE TypeApplications #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | This module defines types and simple operations over constraints, as used
 -- in the type-checker and constraint solver.
 module GHC.Tc.Types.Constraint (
diff --git a/compiler/GHC/Tc/Types/Origin.hs b/compiler/GHC/Tc/Types/Origin.hs
index ce16837805..6c7759db31 100644
--- a/compiler/GHC/Tc/Types/Origin.hs
+++ b/compiler/GHC/Tc/Types/Origin.hs
@@ -3,9 +3,6 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE PolyKinds #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 -- | Describes the provenance of types as they flow through the type-checker.
 -- The datatypes here are mainly used for error message generation.
 module GHC.Tc.Types.Origin (
diff --git a/compiler/GHC/Tc/Utils/Instantiate.hs b/compiler/GHC/Tc/Utils/Instantiate.hs
index d5e8e182e9..abbee42526 100644
--- a/compiler/GHC/Tc/Utils/Instantiate.hs
+++ b/compiler/GHC/Tc/Utils/Instantiate.hs
@@ -2,7 +2,6 @@
 {-# LANGUAGE DisambiguateRecordFields #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/Tc/Utils/Monad.hs b/compiler/GHC/Tc/Utils/Monad.hs
index 2f61ff8777..2c34b15f6f 100644
--- a/compiler/GHC/Tc/Utils/Monad.hs
+++ b/compiler/GHC/Tc/Utils/Monad.hs
@@ -4,7 +4,6 @@
 {-# LANGUAGE RecordWildCards   #-}
 
 {-# OPTIONS_GHC -fno-warn-orphans #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 {-
 (c) The University of Glasgow 2006
diff --git a/compiler/GHC/Tc/Utils/TcType.hs b/compiler/GHC/Tc/Utils/TcType.hs
index 5c1e13ab76..98b8e2ae76 100644
--- a/compiler/GHC/Tc/Utils/TcType.hs
+++ b/compiler/GHC/Tc/Utils/TcType.hs
@@ -3,8 +3,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections       #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/Tc/Utils/Unify.hs b/compiler/GHC/Tc/Utils/Unify.hs
index 61787d299f..f7e1ec938a 100644
--- a/compiler/GHC/Tc/Utils/Unify.hs
+++ b/compiler/GHC/Tc/Utils/Unify.hs
@@ -2,9 +2,6 @@
 {-# LANGUAGE TupleSections       #-}
 {-# LANGUAGE RecursiveDo         #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
diff --git a/compiler/GHC/Tc/Validity.hs b/compiler/GHC/Tc/Validity.hs
index 5072b8eeff..15168ddd2f 100644
--- a/compiler/GHC/Tc/Validity.hs
+++ b/compiler/GHC/Tc/Validity.hs
@@ -1734,15 +1734,12 @@ synonyms, by matching on TyConApp directly.
 -}
 
 checkValidInstance :: UserTypeCtxt -> LHsSigType GhcRn -> Type -> TcM ()
-checkValidInstance ctxt hs_type ty
-  | not is_tc_app
-  = failWithTc (TcRnNoClassInstHead tau)
-
-  | isNothing mb_cls
-  = failWithTc (TcRnIllegalClassInst (tyConFlavour tc))
-
-  | otherwise
-  = do  { setSrcSpanA head_loc $
+checkValidInstance ctxt hs_type ty = case tau of
+  -- See Note [Instances and constraint synonyms]
+  TyConApp tc inst_tys -> case tyConClass_maybe tc of
+    Nothing -> failWithTc (TcRnIllegalClassInst (tyConFlavour tc))
+    Just clas -> do
+        { setSrcSpanA head_loc $
           checkValidInstHead ctxt clas inst_tys
 
         ; traceTc "checkValidInstance {" (ppr ty)
@@ -1775,12 +1772,9 @@ checkValidInstance ctxt hs_type ty
         ; traceTc "End checkValidInstance }" empty
 
         ; return () }
+  _ -> failWithTc (TcRnNoClassInstHead tau)
   where
     (_tvs, theta, tau)   = tcSplitSigmaTy ty
-    is_tc_app            = case tau of { TyConApp {} -> True; _ -> False }
-    TyConApp tc inst_tys = tau   -- See Note [Instances and constraint synonyms]
-    mb_cls               = tyConClass_maybe tc
-    Just clas            = mb_cls
 
         -- The location of the "head" of the instance
     head_loc = getLoc (getLHsInstDeclHead hs_type)
diff --git a/compiler/GHC/ThToHs.hs b/compiler/GHC/ThToHs.hs
index 6642ce84b1..0a1fb615ec 100644
--- a/compiler/GHC/ThToHs.hs
+++ b/compiler/GHC/ThToHs.hs
@@ -9,7 +9,6 @@
 {-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 
 {-
 (c) The University of Glasgow 2006
@@ -28,7 +27,7 @@ module GHC.ThToHs
    )
 where
 
-import GHC.Prelude
+import GHC.Prelude hiding (head, init, last, tail)
 
 import GHC.Hs as Hs
 import GHC.Builtin.Names
@@ -62,6 +61,7 @@ import Control.Applicative( (<|>) )
 import Data.Bifunctor (first)
 import Data.Foldable (for_)
 import Data.List.NonEmpty( NonEmpty (..), nonEmpty )
+import qualified Data.List.NonEmpty as NE
 import Data.Maybe( catMaybes, isNothing )
 import Language.Haskell.TH as TH hiding (sigP)
 import Language.Haskell.TH.Syntax as TH
@@ -1224,11 +1224,12 @@ cvtOpApp x op y
 -------------------------------------
 
 cvtHsDo :: HsDoFlavour -> [TH.Stmt] -> CvtM (HsExpr GhcPs)
-cvtHsDo do_or_lc stmts
-  | null stmts = failWith EmptyStmtListInDoBlock
-  | otherwise
-  = do  { stmts' <- cvtStmts stmts
-        ; let Just (stmts'', last') = snocView stmts'
+cvtHsDo do_or_lc stmts = case nonEmpty stmts of
+    Nothing -> failWith EmptyStmtListInDoBlock
+    Just stmts -> do
+        { stmts' <- traverse cvtStmt stmts
+        ; let stmts'' = NE.init stmts'
+              last' = NE.last stmts'
 
         ; last'' <- case last' of
                     (L loc (BodyStmt _ body _ _))
diff --git a/compiler/GHC/Types/Basic.hs b/compiler/GHC/Types/Basic.hs
index 88baab297c..1ad6b608fc 100644
--- a/compiler/GHC/Types/Basic.hs
+++ b/compiler/GHC/Types/Basic.hs
@@ -20,8 +20,6 @@ types that
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Types.Basic (
         LeftOrRight(..),
         pickLR,
diff --git a/compiler/GHC/Types/RepType.hs b/compiler/GHC/Types/RepType.hs
index 9c394771cf..a5e39f5c63 100644
--- a/compiler/GHC/Types/RepType.hs
+++ b/compiler/GHC/Types/RepType.hs
@@ -56,6 +56,7 @@ import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 
+import Data.List.NonEmpty (NonEmpty (..))
 import Data.List (sort)
 import qualified Data.IntSet as IS
 
@@ -203,14 +204,14 @@ type SortedSlotTys = [SlotTy]
 --
 -- INVARIANT: Result slots are sorted (via Ord SlotTy), except that at the head
 -- of the list we have the slot for the tag.
-ubxSumRepType :: [[PrimRep]] -> [SlotTy]
+ubxSumRepType :: [[PrimRep]] -> NonEmpty SlotTy
 ubxSumRepType constrs0
   -- These first two cases never classify an actual unboxed sum, which always
   -- has at least two disjuncts. But it could happen if a user writes, e.g.,
   -- forall (a :: TYPE (SumRep [IntRep])). ...
   -- which could never be instantiated. We still don't want to panic.
   | constrs0 `lengthLessThan` 2
-  = [WordSlot]
+  = WordSlot :| []
 
   | otherwise
   = let
@@ -238,7 +239,7 @@ ubxSumRepType constrs0
       rep :: [PrimRep] -> SortedSlotTys
       rep ty = sort (map primRepSlot ty)
 
-      sumRep = WordSlot : combine_alts (map rep constrs0)
+      sumRep = WordSlot :| combine_alts (map rep constrs0)
                -- WordSlot: for the tag of the sum
     in
       sumRep
diff --git a/compiler/GHC/Types/Var.hs b/compiler/GHC/Types/Var.hs
index 494ee70ccf..69ba5b0d22 100644
--- a/compiler/GHC/Types/Var.hs
+++ b/compiler/GHC/Types/Var.hs
@@ -7,7 +7,6 @@
 
 {-# LANGUAGE FlexibleContexts, MultiWayIf, FlexibleInstances, DeriveDataTypeable,
              PatternSynonyms, BangPatterns #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
 -- |
diff --git a/compiler/GHC/Utils/Misc.hs b/compiler/GHC/Utils/Misc.hs
index da532279f7..0d5eabeb0b 100644
--- a/compiler/GHC/Utils/Misc.hs
+++ b/compiler/GHC/Utils/Misc.hs
@@ -7,8 +7,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE MagicHash #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 -- | Highly random utility functions
 --
 module GHC.Utils.Misc (
@@ -17,9 +15,7 @@ module GHC.Utils.Misc (
 
         -- * General list processing
         zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
-        zipLazy, stretchZipWith, zipWithAndUnzip, zipAndUnzip,
-
-        zipWithLazy, zipWith3Lazy,
+        stretchZipWith, zipWithAndUnzip, zipAndUnzip,
 
         filterByList, filterByLists, partitionByList,
 
@@ -262,25 +258,6 @@ zipWith4Equal _   _ [] [] [] [] =  []
 zipWith4Equal msg _ _  _  _  _  =  panic ("zipWith4Equal: unequal lists: "++msg)
 #endif
 
--- | 'zipLazy' is a kind of 'zip' that is lazy in the second list (observe the ~)
-zipLazy :: [a] -> [b] -> [(a,b)]
-zipLazy []     _       = []
-zipLazy (x:xs) ~(y:ys) = (x,y) : zipLazy xs ys
-
--- | 'zipWithLazy' is like 'zipWith' but is lazy in the second list.
--- The length of the output is always the same as the length of the first
--- list.
-zipWithLazy :: (a -> b -> c) -> [a] -> [b] -> [c]
-zipWithLazy _ []     _       = []
-zipWithLazy f (a:as) ~(b:bs) = f a b : zipWithLazy f as bs
-
--- | 'zipWith3Lazy' is like 'zipWith3' but is lazy in the second and third lists.
--- The length of the output is always the same as the length of the first
--- list.
-zipWith3Lazy :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d]
-zipWith3Lazy _ []     _       _       = []
-zipWith3Lazy f (a:as) ~(b:bs) ~(c:cs) = f a b c : zipWith3Lazy f as bs cs
-
 -- | 'filterByList' takes a list of Bools and a list of some elements and
 -- filters out these elements for which the corresponding value in the list of
 -- Bools is False. This function does not check whether the lists have equal
diff --git a/compiler/Language/Haskell/Syntax/Decls.hs b/compiler/Language/Haskell/Syntax/Decls.hs
index 012304edf4..21a03c9c22 100644
--- a/compiler/Language/Haskell/Syntax/Decls.hs
+++ b/compiler/Language/Haskell/Syntax/Decls.hs
@@ -19,9 +19,6 @@
 (c) The GRASP/@type@AQUA Project, Glasgow University, 1992-1998
 -}
 
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.*
 
 -- | Abstract syntax of global declarations.
diff --git a/compiler/Language/Haskell/Syntax/Expr.hs b/compiler/Language/Haskell/Syntax/Expr.hs
index 5a22e35c74..ba818e82c5 100644
--- a/compiler/Language/Haskell/Syntax/Expr.hs
+++ b/compiler/Language/Haskell/Syntax/Expr.hs
@@ -10,8 +10,6 @@
 {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
                                       -- in module Language.Haskell.Syntax.Extension
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998