Lint the compiler for extraneous LANGUAGE pragmas

145 files changed, 781 insertions, 782 deletions

diff --git a/compiler/.hlint.yaml b/compiler/.hlint.yaml
new file mode 100644
index 0000000000..6ebe02e94c
--- /dev/null
+++ b/compiler/.hlint.yaml
@@ -0,0 +1,7 @@
+# HLint configuration file
+# https://github.com/ndmitchell/hlint
+##########################
+
+- ignore: {}
+- warn: {name: Unused LANGUAGE pragma}
+- warn: {name: Use fewer LANGUAGE pragmas}
diff --git a/compiler/GHC/ByteCode/Asm.hs b/compiler/GHC/ByteCode/Asm.hs
index e27af3ad1b..9ad8615d55 100644
--- a/compiler/GHC/ByteCode/Asm.hs
+++ b/compiler/GHC/ByteCode/Asm.hs
@@ -1,4 +1,6 @@
-{-# LANGUAGE BangPatterns, CPP, DeriveFunctor, MagicHash, RecordWildCards #-}
+{-# LANGUAGE CPP             #-}
+{-# LANGUAGE DeriveFunctor   #-}
+{-# LANGUAGE RecordWildCards #-}
 {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-}
 --
 --  (c) The University of Glasgow 2002-2006
diff --git a/compiler/GHC/ByteCode/InfoTable.hs b/compiler/GHC/ByteCode/InfoTable.hs
index 02b2e236b9..567209adda 100644
--- a/compiler/GHC/ByteCode/InfoTable.hs
+++ b/compiler/GHC/ByteCode/InfoTable.hs
@@ -1,4 +1,5 @@
-{-# LANGUAGE CPP, MagicHash, ScopedTypeVariables #-}
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-}
 --
 --  (c) The University of Glasgow 2002-2006
diff --git a/compiler/GHC/ByteCode/Instr.hs b/compiler/GHC/ByteCode/Instr.hs
index 8aa78749aa..e4c3de7913 100644
--- a/compiler/GHC/ByteCode/Instr.hs
+++ b/compiler/GHC/ByteCode/Instr.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, MagicHash #-}
+{-# LANGUAGE CPP #-}
 {-# OPTIONS_GHC -funbox-strict-fields #-}
 --
 --  (c) The University of Glasgow 2002-2006
diff --git a/compiler/GHC/ByteCode/Linker.hs b/compiler/GHC/ByteCode/Linker.hs
index bf7ef712fc..a158886369 100644
--- a/compiler/GHC/ByteCode/Linker.hs
+++ b/compiler/GHC/ByteCode/Linker.hs
@@ -1,7 +1,6 @@
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE CPP                   #-}
+{-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE MagicHash             #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-}
 --
diff --git a/compiler/GHC/ByteCode/Types.hs b/compiler/GHC/ByteCode/Types.hs
index 296f886a29..80361c3a6b 100644
--- a/compiler/GHC/ByteCode/Types.hs
+++ b/compiler/GHC/ByteCode/Types.hs
@@ -1,4 +1,5 @@
-{-# LANGUAGE MagicHash, RecordWildCards, GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE RecordWildCards            #-}
 --
 --  (c) The University of Glasgow 2002-2006
 --
diff --git a/compiler/GHC/Cmm/CLabel.hs b/compiler/GHC/Cmm/CLabel.hs
index 9a65369246..7a3e55dcf9 100644
--- a/compiler/GHC/Cmm/CLabel.hs
+++ b/compiler/GHC/Cmm/CLabel.hs
@@ -1569,12 +1569,12 @@ T15155.a [InlPrag=NOINLINE] :: T15155.A
 
 The emitted assembly is
 
-#### INDIRECTEE
+==== INDIRECTEE
 a1_rXq_closure:                         -- module local haskell value
         .quad   GHC.Types.I#_con_info   -- an Int
         .quad   42
 
-#### BEFORE
+==== BEFORE
 .globl T15155.a_closure                 -- exported newtype wrapped value
 T15155.a_closure:
         .quad   stg_IND_STATIC_info     -- the closure info
@@ -1582,7 +1582,7 @@ T15155.a_closure:
         .quad   0
         .quad   0
 
-#### AFTER
+==== AFTER
 .globl T15155.a_closure                 -- exported newtype wrapped value
 .equiv a1_rXq_closure,T15155.a_closure  -- both are shared
 
diff --git a/compiler/GHC/Cmm/Dataflow/Collections.hs b/compiler/GHC/Cmm/Dataflow/Collections.hs
index 1fb8f5d52c..a7aa2716c9 100644
--- a/compiler/GHC/Cmm/Dataflow/Collections.hs
+++ b/compiler/GHC/Cmm/Dataflow/Collections.hs
@@ -1,8 +1,6 @@
-{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE DeriveFoldable #-}
-{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
 
 module GHC.Cmm.Dataflow.Collections
     ( IsSet(..)
diff --git a/compiler/GHC/Cmm/Dataflow/Label.hs b/compiler/GHC/Cmm/Dataflow/Label.hs
index 148fc15ede..161125daff 100644
--- a/compiler/GHC/Cmm/Dataflow/Label.hs
+++ b/compiler/GHC/Cmm/Dataflow/Label.hs
@@ -1,11 +1,8 @@
-{-# LANGUAGE DeriveFoldable #-}
-{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE FlexibleInstances #-}
-
+{-# LANGUAGE TypeFamilies #-}
 
 module GHC.Cmm.Dataflow.Label
     ( Label
diff --git a/compiler/GHC/Cmm/Node.hs b/compiler/GHC/Cmm/Node.hs
index 9e5b709385..61b4030620 100644
--- a/compiler/GHC/Cmm/Node.hs
+++ b/compiler/GHC/Cmm/Node.hs
@@ -1,13 +1,12 @@
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE ExplicitForAll #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE ScopedTypeVariables #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
diff --git a/compiler/GHC/Cmm/Pipeline.hs b/compiler/GHC/Cmm/Pipeline.hs
index b3f9606512..f5cf20a6b6 100644
--- a/compiler/GHC/Cmm/Pipeline.hs
+++ b/compiler/GHC/Cmm/Pipeline.hs
@@ -1,6 +1,4 @@
 {-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE TupleSections #-}
 
 module GHC.Cmm.Pipeline (
   -- | Converts C-- with an implicit stack and native C-- calls into
diff --git a/compiler/GHC/CmmToAsm/BlockLayout.hs b/compiler/GHC/CmmToAsm/BlockLayout.hs
index 2e05d2dfa9..0a71d00449 100644
--- a/compiler/GHC/CmmToAsm/BlockLayout.hs
+++ b/compiler/GHC/CmmToAsm/BlockLayout.hs
@@ -1,14 +1,13 @@
---
--- Copyright (c) 2018 Andreas Klebinger
---
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE DataKinds #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE MultiWayIf #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
+
+--
+-- Copyright (c) 2018 Andreas Klebinger
+--
 
 module GHC.CmmToAsm.BlockLayout
     ( sequenceTop, backendMaintainsCfg)
diff --git a/compiler/GHC/CmmToAsm/CFG.hs b/compiler/GHC/CmmToAsm/CFG.hs
index cc38256d85..870897cceb 100644
--- a/compiler/GHC/CmmToAsm/CFG.hs
+++ b/compiler/GHC/CmmToAsm/CFG.hs
@@ -1,15 +1,13 @@
+{-# LANGUAGE CPP                        #-}
+{-# LANGUAGE DataKinds                  #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE Rank2Types                 #-}
+{-# LANGUAGE ScopedTypeVariables        #-}
+{-# LANGUAGE TypeFamilies               #-}
 --
 -- Copyright (c) 2018 Andreas Klebinger
 --
 
-{-# LANGUAGE TypeFamilies, ScopedTypeVariables #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE Rank2Types #-}
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE DataKinds #-}
-
 module GHC.CmmToAsm.CFG
     ( CFG, CfgEdge(..), EdgeInfo(..), EdgeWeight(..)
     , TransitionSource(..)
diff --git a/compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs b/compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs
index 872b01c11a..d17aebd87c 100644
--- a/compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs
@@ -1,4 +1,6 @@
-{-# LANGUAGE ScopedTypeVariables, GADTs, BangPatterns #-}
+{-# LANGUAGE GADTs               #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
 module GHC.CmmToAsm.Reg.Graph.SpillCost (
         SpillCostRecord,
         plusSpillCostRecord,
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs b/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
index 0cc155aa07..fc9f9c0f89 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-
 -- | Free regs map for PowerPC
 module GHC.CmmToAsm.Reg.Linear.PPC where
 
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs b/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
index 0bb4448d6e..a2a0ee73f9 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 
 -- | Free regs map for SPARC
 module GHC.CmmToAsm.Reg.Linear.SPARC where
diff --git a/compiler/GHC/CmmToC.hs b/compiler/GHC/CmmToC.hs
index 6aa4f9b729..0da229130b 100644
--- a/compiler/GHC/CmmToC.hs
+++ b/compiler/GHC/CmmToC.hs
@@ -1,5 +1,7 @@
-{-# LANGUAGE CPP, DeriveFunctor, GADTs, PatternSynonyms #-}
-{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE CPP           #-}
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE GADTs         #-}
+{-# LANGUAGE LambdaCase    #-}
 
 -----------------------------------------------------------------------------
 --
diff --git a/compiler/GHC/Core/Coercion.hs b/compiler/GHC/Core/Coercion.hs
index 381e80d07a..401eed8edb 100644
--- a/compiler/GHC/Core/Coercion.hs
+++ b/compiler/GHC/Core/Coercion.hs
@@ -1,10 +1,12 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE RankNTypes          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
 {-
 (c) The University of Glasgow 2006
 -}
 
-{-# LANGUAGE RankNTypes, CPP, MultiWayIf, FlexibleContexts, BangPatterns,
-             ScopedTypeVariables #-}
-
 -- | Module for (a) type kinds and (b) type coercions,
 -- as used in System FC. See 'GHC.Core.Expr' for
 -- more on System FC and how coercions fit into it.
diff --git a/compiler/GHC/Core/Coercion/Axiom.hs b/compiler/GHC/Core/Coercion/Axiom.hs
index 2bf31f8cc1..3221eab4b2 100644
--- a/compiler/GHC/Core/Coercion/Axiom.hs
+++ b/compiler/GHC/Core/Coercion/Axiom.hs
@@ -1,7 +1,12 @@
--- (c) The University of Glasgow 2012
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE DeriveDataTypeable  #-}
+{-# LANGUAGE GADTs               #-}
+{-# LANGUAGE KindSignatures      #-}
+{-# LANGUAGE RoleAnnotations     #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
-{-# LANGUAGE CPP, DataKinds, DeriveDataTypeable, GADTs, KindSignatures,
-             ScopedTypeVariables, StandaloneDeriving, RoleAnnotations #-}
+-- (c) The University of Glasgow 2012
 
 -- | Module for coercion axioms, used to represent type family instances
 -- and newtypes
diff --git a/compiler/GHC/Core/FamInstEnv.hs b/compiler/GHC/Core/FamInstEnv.hs
index 75ad0a5574..8b9af440cc 100644
--- a/compiler/GHC/Core/FamInstEnv.hs
+++ b/compiler/GHC/Core/FamInstEnv.hs
@@ -1,12 +1,14 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DeriveFunctor       #-}
+{-# LANGUAGE GADTs               #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TupleSections       #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 -- (c) The University of Glasgow 2006
 --
 -- FamInstEnv: Type checked family instance declarations
 
-{-# LANGUAGE CPP, GADTs, ScopedTypeVariables, BangPatterns, TupleSections,
-    DeriveFunctor #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Core.FamInstEnv (
         FamInst(..), FamFlavor(..), famInstAxiom, famInstTyCon, famInstRHS,
         famInstsRepTyCons, famInstRepTyCon_maybe, dataFamInstRepTyCon,
diff --git a/compiler/GHC/Core/Lint.hs b/compiler/GHC/Core/Lint.hs
index 7f8fb351e0..0a1d5d0ddb 100644
--- a/compiler/GHC/Core/Lint.hs
+++ b/compiler/GHC/Core/Lint.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DeriveFunctor       #-}
+{-# LANGUAGE MultiWayIf          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
@@ -7,9 +12,6 @@ A ``lint'' pass to check for Core correctness.
 See Note [Core Lint guarantee].
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns, ScopedTypeVariables, DeriveFunctor, MultiWayIf #-}
-
 module GHC.Core.Lint (
     lintCoreBindings, lintUnfolding,
     lintPassResult, lintInteractiveExpr, lintExpr,
@@ -1864,14 +1866,14 @@ lintCoreRule fun fun_ty rule@(Rule { ru_name = name, ru_bndrs = bndrs
 ~~~~~~~~~~~~~~~~~~~~~~~
 It's very bad if simplifying a rule means that one of the template
 variables (ru_bndrs) that /is/ mentioned on the RHS becomes
-not-mentioned in the LHS (ru_args).  How can that happen?  Well, in
-#10602, SpecConstr stupidly constructed a rule like
+not-mentioned in the LHS (ru_args).  How can that happen?  Well, in #10602,
+SpecConstr stupidly constructed a rule like
 
   forall x,c1,c2.
      f (x |> c1 |> c2) = ....
 
-But simplExpr collapses those coercions into one.  (Indeed in
-#10602, it collapsed to the identity and was removed altogether.)
+But simplExpr collapses those coercions into one.  (Indeed in #10602,
+it collapsed to the identity and was removed altogether.)
 
 We don't have a great story for what to do here, but at least
 this check will nail it.
diff --git a/compiler/GHC/Core/Map.hs b/compiler/GHC/Core/Map.hs
index ad5cd6fd53..d053aecb82 100644
--- a/compiler/GHC/Core/Map.hs
+++ b/compiler/GHC/Core/Map.hs
@@ -1,16 +1,15 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
--}
-
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeSynonymInstances #-}
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+-}
 
 module GHC.Core.Map (
    -- * Maps over Core expressions
diff --git a/compiler/GHC/Core/Multiplicity.hs b/compiler/GHC/Core/Multiplicity.hs
index 73535a3e15..881966f8ff 100644
--- a/compiler/GHC/Core/Multiplicity.hs
+++ b/compiler/GHC/Core/Multiplicity.hs
@@ -1,5 +1,4 @@
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE PatternSynonyms, ViewPatterns #-}
+{-# LANGUAGE PatternSynonyms    #-}
 
 {-|
 This module defines the semi-ring of multiplicities, and associated functions.
diff --git a/compiler/GHC/Core/Opt/Exitify.hs b/compiler/GHC/Core/Opt/Exitify.hs
index e489cf298f..60b1e7a61c 100644
--- a/compiler/GHC/Core/Opt/Exitify.hs
+++ b/compiler/GHC/Core/Opt/Exitify.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE PatternSynonyms #-}
-
 module GHC.Core.Opt.Exitify ( exitifyProgram ) where
 
 {-
diff --git a/compiler/GHC/Core/Opt/OccurAnal.hs b/compiler/GHC/Core/Opt/OccurAnal.hs
index e352910cfb..97d38c8bd1 100644
--- a/compiler/GHC/Core/Opt/OccurAnal.hs
+++ b/compiler/GHC/Core/Opt/OccurAnal.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP          #-}
+{-# LANGUAGE ViewPatterns #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -11,9 +17,6 @@ The occurrence analyser re-typechecks a core expression, returning a new
 core expression with (hopefully) improved usage information.
 -}
 
-{-# LANGUAGE CPP, BangPatterns, MultiWayIf, ViewPatterns  #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 module GHC.Core.Opt.OccurAnal ( occurAnalysePgm, occurAnalyseExpr ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/Core/Opt/SetLevels.hs b/compiler/GHC/Core/Opt/SetLevels.hs
index f678433568..0a4d4541f4 100644
--- a/compiler/GHC/Core/Opt/SetLevels.hs
+++ b/compiler/GHC/Core/Opt/SetLevels.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP             #-}
+{-# LANGUAGE PatternSynonyms #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -60,9 +65,6 @@
   identity.
 -}
 
-{-# LANGUAGE CPP, MultiWayIf, PatternSynonyms #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 module GHC.Core.Opt.SetLevels (
         setLevels,
 
@@ -882,9 +884,8 @@ float a boxed version
 and replace the original (f x) with
    case (case y of I# r -> r) of r -> blah
 
-Being able to float unboxed expressions is sometimes important; see
-#12603.  I'm not sure how /often/ it is important, but it's
-not hard to achieve.
+Being able to float unboxed expressions is sometimes important; see #12603.
+I'm not sure how /often/ it is important, but it's not hard to achieve.
 
 We only do it for a fixed collection of types for which we have a
 convenient boxing constructor (see boxingDataCon_maybe).  In
diff --git a/compiler/GHC/Core/Opt/Simplify/Utils.hs b/compiler/GHC/Core/Opt/Simplify/Utils.hs
index 420d406eed..41ef2291e0 100644
--- a/compiler/GHC/Core/Opt/Simplify/Utils.hs
+++ b/compiler/GHC/Core/Opt/Simplify/Utils.hs
@@ -1207,8 +1207,7 @@ Here f occurs just once, in the RHS of fInt. But if we inline it there
 it might make fInt look big, and we'll lose the opportunity to inline f
 at each of fInt's call sites.  The INLINE pragma will only inline when
 the application is saturated for exactly this reason; and we don't
-want PreInlineUnconditionally to second-guess it.  A live example is
-#3736.
+want PreInlineUnconditionally to second-guess it. A live example is #3736.
     c.f. Note [Stable unfoldings and postInlineUnconditionally]
 
 NB: if the pragma is INLINEABLE, then we don't want to behave in
diff --git a/compiler/GHC/Core/Opt/Specialise.hs b/compiler/GHC/Core/Opt/Specialise.hs
index 30e9689619..57c49cd5c9 100644
--- a/compiler/GHC/Core/Opt/Specialise.hs
+++ b/compiler/GHC/Core/Opt/Specialise.hs
@@ -1,15 +1,13 @@
+{-# LANGUAGE CPP #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
 
 \section[Specialise]{Stamping out overloading, and (optionally) polymorphism}
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE PatternSynonyms #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 module GHC.Core.Opt.Specialise ( specProgram, specUnfolding ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/Core/Opt/StaticArgs.hs b/compiler/GHC/Core/Opt/StaticArgs.hs
index 91c8646f19..04b21b588e 100644
--- a/compiler/GHC/Core/Opt/StaticArgs.hs
+++ b/compiler/GHC/Core/Opt/StaticArgs.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -48,7 +50,6 @@ The previous patch, to fix polymorphic floatout demand signatures, is
 essential to make this work well!
 -}
 
-{-# LANGUAGE CPP, PatternSynonyms #-}
 module GHC.Core.Opt.StaticArgs ( doStaticArgs ) where
 
 import GHC.Prelude
diff --git a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
index 231faa0d44..490ca1a189 100644
--- a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
+++ b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
@@ -924,15 +924,13 @@ which can still be specialised by the type-class specialiser, something like
 
 BUT if f is strict in the Ord dictionary, we might unpack it, to get
    fw :: (a->a->Bool) -> [a] -> Int# -> a
-and the type-class specialiser can't specialise that.  An example is
-#6056.
+and the type-class specialiser can't specialise that. An example is #6056.
 
 But in any other situation a dictionary is just an ordinary value,
 and can be unpacked.  So we track the INLINABLE pragma, and switch
 off the unpacking in mkWWstr_one (see the isClassPred test).
 
-Historical note: #14955 describes how I got this fix wrong
-the first time.
+Historical note: #14955 describes how I got this fix wrong the first time.
 -}
 
 -- | Context for a 'DataCon' application with a hole for every field, including
diff --git a/compiler/GHC/Core/Ppr.hs b/compiler/GHC/Core/Ppr.hs
index 79c5acae23..37e5afc963 100644
--- a/compiler/GHC/Core/Ppr.hs
+++ b/compiler/GHC/Core/Ppr.hs
@@ -1,3 +1,6 @@
+{-# LANGUAGE LambdaCase #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The AQUA Project, Glasgow University, 1996-1998
@@ -6,10 +9,6 @@
 Printing of Core syntax
 -}
 
-{-# LANGUAGE MultiWayIf #-}
-{-# LANGUAGE LambdaCase #-}
-{-# OPTIONS_GHC -fno-warn-orphans #-}
-
 module GHC.Core.Ppr (
         pprCoreExpr, pprParendExpr,
         pprCoreBinding, pprCoreBindings, pprCoreAlt,
diff --git a/compiler/GHC/Core/TyCo/Rep.hs b/compiler/GHC/Core/TyCo/Rep.hs
index 87cd0ed6bb..9503ba4ccf 100644
--- a/compiler/GHC/Core/TyCo/Rep.hs
+++ b/compiler/GHC/Core/TyCo/Rep.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP                #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+
+{-# OPTIONS_HADDOCK not-home #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1998
@@ -18,9 +23,6 @@ Note [The Type-related module hierarchy]
 -}
 
 -- We expose the relevant stuff from this module via the Type module
-{-# OPTIONS_HADDOCK not-home #-}
-{-# LANGUAGE CPP, MultiWayIf, PatternSynonyms, BangPatterns, DeriveDataTypeable #-}
-
 module GHC.Core.TyCo.Rep (
         TyThing(..), tyThingCategory, pprTyThingCategory, pprShortTyThing,
 
diff --git a/compiler/GHC/Core/TyCon.hs b/compiler/GHC/Core/TyCon.hs
index 919407376e..ad455779b7 100644
--- a/compiler/GHC/Core/TyCon.hs
+++ b/compiler/GHC/Core/TyCon.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE LambdaCase        #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,9 +10,6 @@
 The @TyCon@ datatype
 -}
 
-{-# LANGUAGE CPP, FlexibleInstances #-}
-{-# LANGUAGE LambdaCase #-}
-
 module GHC.Core.TyCon(
         -- * Main TyCon data types
         TyCon,
diff --git a/compiler/GHC/Core/Unfold.hs b/compiler/GHC/Core/Unfold.hs
index 89e4580351..a410bac6e1 100644
--- a/compiler/GHC/Core/Unfold.hs
+++ b/compiler/GHC/Core/Unfold.hs
@@ -713,8 +713,7 @@ Historical note 2: Much longer ago, Simon M tried a MUCH bigger
 discount: (10 * (10 + n_val_args)), and said it was an "unambiguous
 win", but its terribly dangerous because a function with many many
 case branches, each finishing with a constructor, can have an
-arbitrarily large discount.  This led to terrible code bloat: see
-#6099.
+arbitrarily large discount.  This led to terrible code bloat: see #6099.
 
 Note [Unboxed tuple size and result discount]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/compiler/GHC/Core/UsageEnv.hs b/compiler/GHC/Core/UsageEnv.hs
index e88b55560d..5c2f613247 100644
--- a/compiler/GHC/Core/UsageEnv.hs
+++ b/compiler/GHC/Core/UsageEnv.hs
@@ -1,7 +1,18 @@
-{-# LANGUAGE ViewPatterns #-}
-module GHC.Core.UsageEnv (UsageEnv, addUsage, scaleUsage, zeroUE,
-                          lookupUE, scaleUE, deleteUE, addUE, Usage(..), unitUE,
-                          bottomUE, supUE, supUEs) where
+module GHC.Core.UsageEnv
+  ( Usage(..)
+  , UsageEnv
+  , addUE
+  , addUsage
+  , bottomUE
+  , deleteUE
+  , lookupUE
+  , scaleUE
+  , scaleUsage
+  , supUE
+  , supUEs
+  , unitUE
+  , zeroUE
+  ) where
 
 import Data.Foldable
 import GHC.Prelude
diff --git a/compiler/GHC/CoreToByteCode.hs b/compiler/GHC/CoreToByteCode.hs
index f4c23237c0..284be0ce08 100644
--- a/compiler/GHC/CoreToByteCode.hs
+++ b/compiler/GHC/CoreToByteCode.hs
@@ -1,9 +1,11 @@
-{-# LANGUAGE CPP, MagicHash, RecordWildCards, BangPatterns #-}
-{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE CPP                        #-}
+{-# LANGUAGE DeriveFunctor              #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE RecordWildCards            #-}
+
 {-# OPTIONS_GHC -fprof-auto-top #-}
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 --
 --  (c) The University of Glasgow 2002-2006
 --
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs
index 0b689732a2..05430a5658 100644
--- a/compiler/GHC/CoreToStg/Prep.hs
+++ b/compiler/GHC/CoreToStg/Prep.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP          #-}
+{-# LANGUAGE BangPatterns #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow, 1994-2006
 
@@ -5,10 +10,6 @@
 Core pass to saturate constructors and PrimOps
 -}
 
-{-# LANGUAGE BangPatterns, CPP, MultiWayIf #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.CoreToStg.Prep
    ( corePrepPgm
    , corePrepExpr
diff --git a/compiler/GHC/Data/BooleanFormula.hs b/compiler/GHC/Data/BooleanFormula.hs
index 15c97558eb..7077b6f489 100644
--- a/compiler/GHC/Data/BooleanFormula.hs
+++ b/compiler/GHC/Data/BooleanFormula.hs
@@ -1,5 +1,5 @@
-{-# LANGUAGE DeriveDataTypeable, DeriveFunctor, DeriveFoldable,
-             DeriveTraversable #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveTraversable  #-}
 
 --------------------------------------------------------------------------------
 -- | Boolean formulas without quantifiers and without negation.
diff --git a/compiler/GHC/Data/TrieMap.hs b/compiler/GHC/Data/TrieMap.hs
index b3c7c5277f..340828ee95 100644
--- a/compiler/GHC/Data/TrieMap.hs
+++ b/compiler/GHC/Data/TrieMap.hs
@@ -1,14 +1,13 @@
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE RankNTypes           #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
-
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
 module GHC.Data.TrieMap(
    -- * Maps over 'Maybe' values
    MaybeMap,
diff --git a/compiler/GHC/Driver/Backpack.hs b/compiler/GHC/Driver/Backpack.hs
index 6822c85b65..5b418d9166 100644
--- a/compiler/GHC/Driver/Backpack.hs
+++ b/compiler/GHC/Driver/Backpack.hs
@@ -1,7 +1,6 @@
-{-# LANGUAGE NondecreasingIndentation #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE NondecreasingIndentation #-}
 
 -- | This is the driver for the 'ghc --backpack' mode, which
 -- is a reimplementation of the "package manager" bits of
diff --git a/compiler/GHC/Driver/Main.hs b/compiler/GHC/Driver/Main.hs
index 2299337596..827855a519 100644
--- a/compiler/GHC/Driver/Main.hs
+++ b/compiler/GHC/Driver/Main.hs
@@ -1,4 +1,6 @@
-{-# LANGUAGE BangPatterns, CPP, MagicHash, NondecreasingIndentation #-}
+{-# LANGUAGE CPP                      #-}
+{-# LANGUAGE BangPatterns             #-}
+{-# LANGUAGE NondecreasingIndentation #-}
 {-# OPTIONS_GHC -fprof-auto-top #-}
 
 -------------------------------------------------------------------------------
diff --git a/compiler/GHC/Driver/Pipeline/Monad.hs b/compiler/GHC/Driver/Pipeline/Monad.hs
index 6ee92328bd..2fcf24e85d 100644
--- a/compiler/GHC/Driver/Pipeline/Monad.hs
+++ b/compiler/GHC/Driver/Pipeline/Monad.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE NamedFieldPuns #-}
 -- | The CompPipeline monad and associated ops
 --
 -- Defined in separate module so that it can safely be imported from Hooks
diff --git a/compiler/GHC/Driver/Types.hs b/compiler/GHC/Driver/Types.hs
index 41da5da110..6409e6128c 100644
--- a/compiler/GHC/Driver/Types.hs
+++ b/compiler/GHC/Driver/Types.hs
@@ -1,20 +1,19 @@
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE DataKinds            #-}
+{-# LANGUAGE DeriveFunctor        #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE RecordWildCards      #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-}
+
 {-
 (c) The University of Glasgow, 2006
 
 \section[GHC.Driver.Types]{Types for the per-module compiler}
 -}
 
-{-# LANGUAGE CPP, ScopedTypeVariables #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE DataKinds #-}
-
 -- | Types for the per-module compiler
 module GHC.Driver.Types (
         -- * compilation state
diff --git a/compiler/GHC/Hs/Binds.hs b/compiler/GHC/Hs/Binds.hs
index 6b4985bcf0..a2d46d35ed 100644
--- a/compiler/GHC/Hs/Binds.hs
+++ b/compiler/GHC/Hs/Binds.hs
@@ -1,3 +1,17 @@
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
+{-# LANGUAGE ViewPatterns #-}
+
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -7,21 +21,6 @@
 Datatype for: @BindGroup@, @Bind@, @Sig@, @Bind@.
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.Hs.Binds where
 
 import GHC.Prelude
diff --git a/compiler/GHC/Hs/Decls.hs b/compiler/GHC/Hs/Decls.hs
index c0b8baa435..78a7fd3320 100644
--- a/compiler/GHC/Hs/Decls.hs
+++ b/compiler/GHC/Hs/Decls.hs
@@ -1,20 +1,21 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ConstraintKinds     #-}
+{-# LANGUAGE DeriveDataTypeable  #-}
+{-# LANGUAGE DeriveTraversable   #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE FlexibleInstances   #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving  #-}
+{-# LANGUAGE TypeApplications    #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
 
-{-# LANGUAGE DeriveDataTypeable, DeriveFunctor, DeriveFoldable,
-             DeriveTraversable #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE ScopedTypeVariables #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
diff --git a/compiler/GHC/Hs/Doc.hs b/compiler/GHC/Hs/Doc.hs
index 55571c5128..400df5cdf9 100644
--- a/compiler/GHC/Hs/Doc.hs
+++ b/compiler/GHC/Hs/Doc.hs
@@ -1,6 +1,5 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 
 module GHC.Hs.Doc
   ( HsDocString
diff --git a/compiler/GHC/Hs/Expr.hs b/compiler/GHC/Hs/Expr.hs
index 0ade8a247d..724f37cbd7 100644
--- a/compiler/GHC/Hs/Expr.hs
+++ b/compiler/GHC/Hs/Expr.hs
@@ -1,27 +1,25 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
--}
-
-{-# LANGUAGE CPP, DeriveDataTypeable, ScopedTypeVariables #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE CPP                       #-}
+{-# LANGUAGE ConstraintKinds           #-}
+{-# LANGUAGE DataKinds                 #-}
+{-# LANGUAGE DeriveDataTypeable        #-}
+{-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE FlexibleContexts          #-}
+{-# LANGUAGE FlexibleInstances         #-}
+{-# LANGUAGE LambdaCase                #-}
+{-# LANGUAGE ScopedTypeVariables       #-}
+{-# LANGUAGE StandaloneDeriving        #-}
+{-# LANGUAGE TypeApplications          #-}
+{-# LANGUAGE TypeFamilyDependencies    #-}
 {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
                                       -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE ExistentialQuantification #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE TypeFamilyDependencies #-}
-{-# LANGUAGE LambdaCase #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+-}
+
 -- | Abstract Haskell syntax for expressions.
 module GHC.Hs.Expr where
 
diff --git a/compiler/GHC/Hs/Extension.hs b/compiler/GHC/Hs/Extension.hs
index 13c2f157e5..b0216fe567 100644
--- a/compiler/GHC/Hs/Extension.hs
+++ b/compiler/GHC/Hs/Extension.hs
@@ -1,24 +1,20 @@
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE EmptyCase #-}
-{-# LANGUAGE EmptyDataDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeFamilyDependencies #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE PatternSynonyms #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE UndecidableSuperClasses #-}  -- for IsPass; see Note [NoGhcTc]
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE AllowAmbiguousTypes #-}      -- for pprIfTc, etc.
+{-# LANGUAGE AllowAmbiguousTypes     #-}      -- for pprIfTc, etc.
+{-# LANGUAGE ConstraintKinds         #-}
+{-# LANGUAGE DataKinds               #-}
+{-# LANGUAGE DeriveDataTypeable      #-}
+{-# LANGUAGE EmptyCase               #-}
+{-# LANGUAGE EmptyDataDeriving       #-}
+{-# LANGUAGE FlexibleContexts        #-}
+{-# LANGUAGE FlexibleInstances       #-}
+{-# LANGUAGE GADTs                   #-}
+{-# LANGUAGE MultiParamTypeClasses   #-}
+{-# LANGUAGE RankNTypes              #-}
+{-# LANGUAGE ScopedTypeVariables     #-}
+{-# LANGUAGE TypeApplications        #-}
+{-# LANGUAGE TypeFamilyDependencies  #-}
+{-# LANGUAGE UndecidableSuperClasses #-} -- for IsPass; see Note [NoGhcTc]
+{-# LANGUAGE UndecidableInstances    #-} -- Wrinkle in Note [Trees That Grow]
+                                         -- in module GHC.Hs.Extension
 
 module GHC.Hs.Extension where
 
diff --git a/compiler/GHC/Hs/ImpExp.hs b/compiler/GHC/Hs/ImpExp.hs
index 740aab2b61..1faadf38bd 100644
--- a/compiler/GHC/Hs/ImpExp.hs
+++ b/compiler/GHC/Hs/ImpExp.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,14 +12,6 @@
 GHC.Hs.ImpExp: Abstract syntax: imports, exports, interfaces
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-
 module GHC.Hs.ImpExp where
 
 import GHC.Prelude
diff --git a/compiler/GHC/Hs/Lit.hs b/compiler/GHC/Hs/Lit.hs
index 4ceaac4264..967d41f283 100644
--- a/compiler/GHC/Hs/Lit.hs
+++ b/compiler/GHC/Hs/Lit.hs
@@ -1,3 +1,12 @@
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE ConstraintKinds      #-}
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -5,16 +14,6 @@
 \section[HsLit]{Abstract syntax: source-language literals}
 -}
 
-{-# LANGUAGE CPP, DeriveDataTypeable #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE TypeFamilies #-}
-
 module GHC.Hs.Lit where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/Hs/Pat.hs b/compiler/GHC/Hs/Pat.hs
index 8ce29a72d3..b2507a0865 100644
--- a/compiler/GHC/Hs/Pat.hs
+++ b/compiler/GHC/Hs/Pat.hs
@@ -1,4 +1,17 @@
 
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE ConstraintKinds      #-}
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE DeriveTraversable    #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE LambdaCase           #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE TypeApplications     #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
+{-# LANGUAGE ViewPatterns         #-}
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,23 +19,6 @@
 \section[PatSyntax]{Abstract Haskell syntax---patterns}
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE DeriveFoldable #-}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns      #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE LambdaCase #-}
-
 module GHC.Hs.Pat (
         Pat(..), LPat,
         ConPatTc (..),
diff --git a/compiler/GHC/Hs/Stats.hs b/compiler/GHC/Hs/Stats.hs
index d0737859c1..cb990f9adf 100644
--- a/compiler/GHC/Hs/Stats.hs
+++ b/compiler/GHC/Hs/Stats.hs
@@ -1,13 +1,12 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeFamilies #-}
+
 -- |
 -- Statistics for per-module compilations
 --
 -- (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
 --
 
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.Hs.Stats ( ppSourceStats ) where
 
 import GHC.Prelude
diff --git a/compiler/GHC/Hs/Type.hs b/compiler/GHC/Hs/Type.hs
index f1f688fdea..4fc2580aba 100644
--- a/compiler/GHC/Hs/Type.hs
+++ b/compiler/GHC/Hs/Type.hs
@@ -1,3 +1,14 @@
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE ConstraintKinds      #-}
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE StandaloneDeriving   #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE ViewPatterns         #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,20 +17,6 @@
 GHC.Hs.Type: Abstract syntax: user-defined types
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.Hs.Type (
         Mult, HsScaled(..),
         hsMult, hsScaledThing,
diff --git a/compiler/GHC/HsToCore.hs b/compiler/GHC/HsToCore.hs
index 2fd0a9302b..ac9adfac22 100644
--- a/compiler/GHC/HsToCore.hs
+++ b/compiler/GHC/HsToCore.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP          #-}
+{-# LANGUAGE TypeFamilies #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,11 +11,6 @@
 The Desugarer: turning HsSyn into Core.
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.HsToCore (
     -- * Desugaring operations
     deSugar, deSugarExpr
diff --git a/compiler/GHC/HsToCore/Arrows.hs b/compiler/GHC/HsToCore/Arrows.hs
index 6668e9a11b..52de5f6fb5 100644
--- a/compiler/GHC/HsToCore/Arrows.hs
+++ b/compiler/GHC/HsToCore/Arrows.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE TypeFamilies #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,12 +11,6 @@
 Desugaring arrow commands
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.HsToCore.Arrows ( dsProcExpr ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/HsToCore/Binds.hs b/compiler/GHC/HsToCore/Binds.hs
index 53926361fc..f1140afae1 100644
--- a/compiler/GHC/HsToCore/Binds.hs
+++ b/compiler/GHC/HsToCore/Binds.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP #-}
+{-# 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
@@ -10,13 +16,6 @@ in that the @Rec@/@NonRec@/etc structure is thrown away (whereas at
 lower levels it is preserved with @let@/@letrec@s).
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE FlexibleContexts #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.HsToCore.Binds
    ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsSpec
    , dsHsWrapper, dsTcEvBinds, dsTcEvBinds_s, dsEvBinds, dsMkUserRule
diff --git a/compiler/GHC/HsToCore/Coverage.hs b/compiler/GHC/HsToCore/Coverage.hs
index ae8c5a3b83..a755d27883 100644
--- a/compiler/GHC/HsToCore/Coverage.hs
+++ b/compiler/GHC/HsToCore/Coverage.hs
@@ -1,15 +1,14 @@
+{-# LANGUAGE DeriveFunctor            #-}
+{-# LANGUAGE NondecreasingIndentation #-}
+{-# LANGUAGE TypeFamilies             #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) Galois, 2006
 (c) University of Glasgow, 2007
 -}
 
-{-# LANGUAGE NondecreasingIndentation, RecordWildCards #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE DeriveFunctor #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.HsToCore.Coverage (addTicksToBinds, hpcInitCode) where
 
 import GHC.Prelude as Prelude
diff --git a/compiler/GHC/HsToCore/Expr.hs b/compiler/GHC/HsToCore/Expr.hs
index 694b394c1c..c9868cc381 100644
--- a/compiler/GHC/HsToCore/Expr.hs
+++ b/compiler/GHC/HsToCore/Expr.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP          #-}
+{-# LANGUAGE TypeFamilies #-}
+
+{-# 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
@@ -6,13 +12,6 @@
 Desugaring expressions.
 -}
 
-{-# LANGUAGE CPP, MultiWayIf #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.HsToCore.Expr
    ( dsExpr, dsLExpr, dsLExprNoLP, dsLocalBinds
    , dsValBinds, dsLit, dsSyntaxExpr
diff --git a/compiler/GHC/HsToCore/Foreign/Decl.hs b/compiler/GHC/HsToCore/Foreign/Decl.hs
index 3c46ef5cf9..f97f38d458 100644
--- a/compiler/GHC/HsToCore/Foreign/Decl.hs
+++ b/compiler/GHC/HsToCore/Foreign/Decl.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeFamilies #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The AQUA Project, Glasgow University, 1998
@@ -6,13 +12,6 @@
 Desugaring foreign declarations (see also GHC.HsToCore.Foreign.Call).
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.HsToCore.Foreign.Decl ( dsForeigns ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/HsToCore/GuardedRHSs.hs b/compiler/GHC/HsToCore/GuardedRHSs.hs
index c2ac2f0ef8..4ad474ceb7 100644
--- a/compiler/GHC/HsToCore/GuardedRHSs.hs
+++ b/compiler/GHC/HsToCore/GuardedRHSs.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,9 +8,6 @@
 Matching guarded right-hand-sides (GRHSs)
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.HsToCore.GuardedRHSs ( dsGuarded, dsGRHSs, isTrueLHsExpr ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/HsToCore/ListComp.hs b/compiler/GHC/HsToCore/ListComp.hs
index 19d46c1f2f..1c7cee081e 100644
--- a/compiler/GHC/HsToCore/ListComp.hs
+++ b/compiler/GHC/HsToCore/ListComp.hs
@@ -1,3 +1,6 @@
+{-# LANGUAGE CPP            #-}
+{-# LANGUAGE TypeFamilies   #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,10 +9,6 @@
 Desugaring list comprehensions, monad comprehensions and array comprehensions
 -}
 
-{-# LANGUAGE CPP, NamedFieldPuns #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.HsToCore.ListComp ( dsListComp, dsMonadComp ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/HsToCore/Match.hs b/compiler/GHC/HsToCore/Match.hs
index afc31ec58d..491191d6a7 100644
--- a/compiler/GHC/HsToCore/Match.hs
+++ b/compiler/GHC/HsToCore/Match.hs
@@ -1,20 +1,19 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-
-
-The @match@ function
--}
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE MonadComprehensions #-}
 {-# LANGUAGE OverloadedLists #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# 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
+
+
+The @match@ function
+-}
+
 module GHC.HsToCore.Match
    ( match, matchEquations, matchWrapper, matchSimply
    , matchSinglePat, matchSinglePatVar
diff --git a/compiler/GHC/HsToCore/Match/Constructor.hs b/compiler/GHC/HsToCore/Match/Constructor.hs
index c04f569cf9..ca6ad7f483 100644
--- a/compiler/GHC/HsToCore/Match/Constructor.hs
+++ b/compiler/GHC/HsToCore/Match/Constructor.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE TypeFamilies #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,12 +11,6 @@
 Pattern-matching constructors
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.HsToCore.Match.Constructor ( matchConFamily, matchPatSyn ) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/HsToCore/Match/Literal.hs b/compiler/GHC/HsToCore/Match/Literal.hs
index a56f729f5e..a2bd2f1095 100644
--- a/compiler/GHC/HsToCore/Match/Literal.hs
+++ b/compiler/GHC/HsToCore/Match/Literal.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,11 +11,6 @@
 Pattern-matching literal patterns
 -}
 
-{-# LANGUAGE CPP, ScopedTypeVariables #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.HsToCore.Match.Literal
    ( dsLit, dsOverLit, hsLitKey
    , tidyLitPat, tidyNPat
diff --git a/compiler/GHC/HsToCore/Monad.hs b/compiler/GHC/HsToCore/Monad.hs
index 653d88420f..46af48e15d 100644
--- a/compiler/GHC/HsToCore/Monad.hs
+++ b/compiler/GHC/HsToCore/Monad.hs
@@ -1,3 +1,10 @@
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE LambdaCase #-}
+
+{-# OPTIONS_GHC -fno-warn-orphans #-}  -- instance MonadThings is necessarily an orphan
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,14 +13,6 @@
 Monadery used in desugaring
 -}
 
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -fno-warn-orphans #-}  -- instance MonadThings is necessarily an orphan
-
 module GHC.HsToCore.Monad (
         DsM, mapM, mapAndUnzipM,
         initDs, initDsTc, initTcDsForSolver, initDsWithModGuts, fixDs,
diff --git a/compiler/GHC/HsToCore/Pmc.hs b/compiler/GHC/HsToCore/Pmc.hs
index 6a6e8175bc..6880fafa6a 100644
--- a/compiler/GHC/HsToCore/Pmc.hs
+++ b/compiler/GHC/HsToCore/Pmc.hs
@@ -1,12 +1,7 @@
-{-# LANGUAGE CPP                        #-}
-{-# LANGUAGE GADTs                      #-}
-{-# LANGUAGE TupleSections              #-}
-{-# LANGUAGE ViewPatterns               #-}
-{-# LANGUAGE MultiWayIf                 #-}
-{-# LANGUAGE LambdaCase                 #-}
-{-# LANGUAGE DeriveFunctor              #-}
-{-# LANGUAGE NamedFieldPuns             #-}
-{-# LANGUAGE FlexibleInstances          #-}
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs             #-}
+{-# LANGUAGE LambdaCase        #-}
 
 -- | This module coverage checks pattern matches. It finds
 --
diff --git a/compiler/GHC/HsToCore/Pmc/Check.hs b/compiler/GHC/HsToCore/Pmc/Check.hs
index f228e4471a..3ffd51fe7a 100644
--- a/compiler/GHC/HsToCore/Pmc/Check.hs
+++ b/compiler/GHC/HsToCore/Pmc/Check.hs
@@ -1,12 +1,7 @@
-{-# LANGUAGE CPP                        #-}
-{-# LANGUAGE GADTs                      #-}
-{-# LANGUAGE TupleSections              #-}
-{-# LANGUAGE ViewPatterns               #-}
-{-# LANGUAGE MultiWayIf                 #-}
-{-# LANGUAGE LambdaCase                 #-}
-{-# LANGUAGE DeriveFunctor              #-}
-{-# LANGUAGE NamedFieldPuns             #-}
-{-# LANGUAGE FlexibleInstances          #-}
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE DeriveFunctor     #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs             #-}
 
 -- | Coverage checking step of the
 -- [Lower Your Guards paper](https://dl.acm.org/doi/abs/10.1145/3408989).
diff --git a/compiler/GHC/HsToCore/Pmc/Desugar.hs b/compiler/GHC/HsToCore/Pmc/Desugar.hs
index fa87eae8f0..f08774a647 100644
--- a/compiler/GHC/HsToCore/Pmc/Desugar.hs
+++ b/compiler/GHC/HsToCore/Pmc/Desugar.hs
@@ -1,12 +1,7 @@
-{-# LANGUAGE CPP                        #-}
-{-# LANGUAGE GADTs                      #-}
-{-# LANGUAGE TupleSections              #-}
-{-# LANGUAGE ViewPatterns               #-}
-{-# LANGUAGE MultiWayIf                 #-}
-{-# LANGUAGE LambdaCase                 #-}
-{-# LANGUAGE DeriveFunctor              #-}
-{-# LANGUAGE NamedFieldPuns             #-}
-{-# LANGUAGE FlexibleInstances          #-}
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs             #-}
+{-# LANGUAGE LambdaCase        #-}
 
 -- | Desugaring step of the
 -- [Lower Your Guards paper](https://dl.acm.org/doi/abs/10.1145/3408989).
diff --git a/compiler/GHC/HsToCore/Pmc/Ppr.hs b/compiler/GHC/HsToCore/Pmc/Ppr.hs
index bb30cd61ed..fea1ecfe39 100644
--- a/compiler/GHC/HsToCore/Pmc/Ppr.hs
+++ b/compiler/GHC/HsToCore/Pmc/Ppr.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, ViewPatterns #-}
+{-# LANGUAGE CPP #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
diff --git a/compiler/GHC/HsToCore/Pmc/Solver.hs b/compiler/GHC/HsToCore/Pmc/Solver.hs
index 1126fadc3b..2ac4404926 100644
--- a/compiler/GHC/HsToCore/Pmc/Solver.hs
+++ b/compiler/GHC/HsToCore/Pmc/Solver.hs
@@ -1,12 +1,14 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE LambdaCase          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE ViewPatterns        #-}
+
 {-
 Authors: George Karachalias <george.karachalias@cs.kuleuven.be>
          Sebastian Graf <sgraf1337@gmail.com>
          Ryan Scott <ryan.gl.scott@gmail.com>
 -}
 
-{-# LANGUAGE CPP, LambdaCase, TupleSections, PatternSynonyms, ViewPatterns,
-             MultiWayIf, ScopedTypeVariables, MagicHash #-}
-
 -- | Model refinements type as per the
 -- [Lower Your Guards paper](https://dl.acm.org/doi/abs/10.1145/3408989).
 -- The main export of the module are the functions 'addPhiCtsNablas' for adding
@@ -17,6 +19,7 @@ Authors: George Karachalias <george.karachalias@cs.kuleuven.be>
 -- In terms of the LYG paper, this module is concerned with Sections 3.4, 3.6
 -- and 3.7. E.g., it represents refinement types directly as a bunch of
 -- normalised refinement types 'Nabla'.
+
 module GHC.HsToCore.Pmc.Solver (
 
         Nabla, Nablas(..), initNablas,
diff --git a/compiler/GHC/HsToCore/Pmc/Solver/Types.hs b/compiler/GHC/HsToCore/Pmc/Solver/Types.hs
index 4f92703764..0cefbebd54 100644
--- a/compiler/GHC/HsToCore/Pmc/Solver/Types.hs
+++ b/compiler/GHC/HsToCore/Pmc/Solver/Types.hs
@@ -1,8 +1,6 @@
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE ApplicativeDo       #-}
+{-# LANGUAGE CPP                 #-}
 {-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE ApplicativeDo #-}
 
 -- | Domain types used in "GHC.HsToCore.Pmc.Solver".
 -- The ultimate goal is to define 'Nabla', which models normalised refinement
diff --git a/compiler/GHC/HsToCore/Pmc/Types.hs b/compiler/GHC/HsToCore/Pmc/Types.hs
index 99aeaff85e..abee31839c 100644
--- a/compiler/GHC/HsToCore/Pmc/Types.hs
+++ b/compiler/GHC/HsToCore/Pmc/Types.hs
@@ -1,14 +1,13 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DeriveFunctor       #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE ViewPatterns        #-}
+
 {-
 Author: George Karachalias <george.karachalias@cs.kuleuven.be>
         Sebastian Graf <sgraf1337@gmail.com>
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE DeriveFunctor #-}
-
 -- | Types used through-out pattern match checking. This module is mostly there
 -- to be imported from "GHC.HsToCore.Types". The exposed API is that of
 -- "GHC.HsToCore.Pmc".
diff --git a/compiler/GHC/HsToCore/Pmc/Utils.hs b/compiler/GHC/HsToCore/Pmc/Utils.hs
index d4646bd6e8..aaa2b5bc65 100644
--- a/compiler/GHC/HsToCore/Pmc/Utils.hs
+++ b/compiler/GHC/HsToCore/Pmc/Utils.hs
@@ -1,5 +1,5 @@
-{-# LANGUAGE CPP, LambdaCase, TupleSections, PatternSynonyms, ViewPatterns,
-             MultiWayIf, ScopedTypeVariables, MagicHash #-}
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
 -- | Utility module for the pattern-match coverage checker.
 module GHC.HsToCore.Pmc.Utils (
diff --git a/compiler/GHC/HsToCore/Quote.hs b/compiler/GHC/HsToCore/Quote.hs
index 0ef8db0efe..d10ee63995 100644
--- a/compiler/GHC/HsToCore/Quote.hs
+++ b/compiler/GHC/HsToCore/Quote.hs
@@ -1,15 +1,14 @@
-{-# LANGUAGE CPP, TypeFamilies #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE PatternSynonyms #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE AllowAmbiguousTypes    #-}
+{-# LANGUAGE CPP                    #-}
+{-# LANGUAGE DataKinds              #-}
+{-# LANGUAGE FlexibleContexts       #-}
 {-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE PatternSynonyms        #-}
+{-# LANGUAGE RankNTypes             #-}
+{-# LANGUAGE ScopedTypeVariables    #-}
+{-# LANGUAGE TypeApplications       #-}
+{-# LANGUAGE TypeFamilies           #-}
+{-# LANGUAGE UndecidableInstances   #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
diff --git a/compiler/GHC/HsToCore/Usage.hs b/compiler/GHC/HsToCore/Usage.hs
index c7fc988fe0..64c041902b 100644
--- a/compiler/GHC/HsToCore/Usage.hs
+++ b/compiler/GHC/HsToCore/Usage.hs
@@ -1,6 +1,4 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
diff --git a/compiler/GHC/HsToCore/Utils.hs b/compiler/GHC/HsToCore/Utils.hs
index b4d1b1b761..0e685cc69d 100644
--- a/compiler/GHC/HsToCore/Utils.hs
+++ b/compiler/GHC/HsToCore/Utils.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE TypeFamilies #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -8,12 +13,6 @@ Utilities for desugaring
 This module exports some utility functions of no great interest.
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
 -- | Utility functions for constructing Core syntax, principally for desugaring
 module GHC.HsToCore.Utils (
         EquationInfo(..),
diff --git a/compiler/GHC/Iface/Ext/Ast.hs b/compiler/GHC/Iface/Ext/Ast.hs
index 68bbc103b5..01c5b6102f 100644
--- a/compiler/GHC/Iface/Ext/Ast.hs
+++ b/compiler/GHC/Iface/Ext/Ast.hs
@@ -1,23 +1,22 @@
+{-# LANGUAGE AllowAmbiguousTypes     #-}
+{-# LANGUAGE CPP                     #-}
+{-# LANGUAGE DataKinds               #-}
+{-# LANGUAGE DeriveDataTypeable      #-}
+{-# LANGUAGE FlexibleContexts        #-}
+{-# LANGUAGE FlexibleInstances       #-}
+{-# LANGUAGE GADTs                   #-}
+{-# LANGUAGE OverloadedStrings       #-}
+{-# LANGUAGE ScopedTypeVariables     #-}
+{-# LANGUAGE TypeApplications        #-}
+{-# LANGUAGE TypeFamilies            #-}
+{-# LANGUAGE UndecidableInstances    #-}
+{-# LANGUAGE UndecidableSuperClasses #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 Main functions for .hie file generation
 -}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE UndecidableSuperClasses #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE AllowAmbiguousTypes #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE TupleSections #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
 module GHC.Iface.Ext.Ast ( mkHieFile, mkHieFileWithSource, getCompressedAsts, enrichHie) where
 
diff --git a/compiler/GHC/Iface/Ext/Debug.hs b/compiler/GHC/Iface/Ext/Debug.hs
index b10b4c982c..ef63a3f4dc 100644
--- a/compiler/GHC/Iface/Ext/Debug.hs
+++ b/compiler/GHC/Iface/Ext/Debug.hs
@@ -1,9 +1,9 @@
+{-# LANGUAGE FlexibleContexts   #-}
+{-# LANGUAGE OverloadedStrings  #-}
+
 {-
 Functions to validate and check .hie file ASTs generated by GHC.
 -}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE FlexibleContexts #-}
 
 module GHC.Iface.Ext.Debug where
 
diff --git a/compiler/GHC/Iface/Ext/Types.hs b/compiler/GHC/Iface/Ext/Types.hs
index 75331a273e..7a7fb4bb00 100644
--- a/compiler/GHC/Iface/Ext/Types.hs
+++ b/compiler/GHC/Iface/Ext/Types.hs
@@ -1,16 +1,16 @@
+{-# LANGUAGE DeriveDataTypeable         #-}
+{-# LANGUAGE DeriveTraversable          #-}
+{-# LANGUAGE FlexibleInstances          #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE OverloadedStrings          #-}
+{-# LANGUAGE PatternSynonyms            #-}
+{-# LANGUAGE ScopedTypeVariables        #-}
+
 {-
 Types for the .hie file format are defined here.
 
 For more information see https://gitlab.haskell.org/ghc/ghc/wikis/hie-files
 -}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE PatternSynonyms #-}
 
 module GHC.Iface.Ext.Types where
 
diff --git a/compiler/GHC/Iface/Make.hs b/compiler/GHC/Iface/Make.hs
index cdcf80bb1f..27933fc18e 100644
--- a/compiler/GHC/Iface/Make.hs
+++ b/compiler/GHC/Iface/Make.hs
@@ -1,11 +1,11 @@
+{-# LANGUAGE CPP                      #-}
+{-# LANGUAGE NondecreasingIndentation #-}
+
 {-
 (c) The University of Glasgow 2006-2008
 (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
 -}
 
-{-# LANGUAGE CPP, NondecreasingIndentation #-}
-{-# LANGUAGE MultiWayIf #-}
-
 -- | Module for constructing @ModIface@ values (interface files),
 -- writing them to disk and comparing two versions to see if
 -- recompilation is required.
diff --git a/compiler/GHC/Iface/Rename.hs b/compiler/GHC/Iface/Rename.hs
index cac4f6e438..63ca80af12 100644
--- a/compiler/GHC/Iface/Rename.hs
+++ b/compiler/GHC/Iface/Rename.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE LambdaCase #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
diff --git a/compiler/GHC/Iface/Tidy.hs b/compiler/GHC/Iface/Tidy.hs
index df1db23b33..82f1c18920 100644
--- a/compiler/GHC/Iface/Tidy.hs
+++ b/compiler/GHC/Iface/Tidy.hs
@@ -1,13 +1,14 @@
+{-# LANGUAGE CPP           #-}
+{-# LANGUAGE DeriveFunctor #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 \section{Tidying up Core}
 -}
 
-{-# LANGUAGE CPP, DeriveFunctor, ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.Iface.Tidy (
        mkBootModDetailsTc, tidyProgram
    ) where
diff --git a/compiler/GHC/Iface/Tidy/StaticPtrTable.hs b/compiler/GHC/Iface/Tidy/StaticPtrTable.hs
index 5e40bed45e..b4a0a3c5a4 100644
--- a/compiler/GHC/Iface/Tidy/StaticPtrTable.hs
+++ b/compiler/GHC/Iface/Tidy/StaticPtrTable.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE ViewPatterns  #-}
+
 -- | Code generation for the Static Pointer Table
 --
 -- (c) 2014 I/O Tweag
@@ -45,7 +47,6 @@
 -- > }
 --
 
-{-# LANGUAGE ViewPatterns, TupleSections #-}
 module GHC.Iface.Tidy.StaticPtrTable
     ( sptCreateStaticBinds
     , sptModuleInitCode
diff --git a/compiler/GHC/Llvm/MetaData.hs b/compiler/GHC/Llvm/MetaData.hs
index f4adff45bb..f46ae0a101 100644
--- a/compiler/GHC/Llvm/MetaData.hs
+++ b/compiler/GHC/Llvm/MetaData.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE LambdaCase #-}
 
 module GHC.Llvm.MetaData where
 
diff --git a/compiler/GHC/Llvm/Types.hs b/compiler/GHC/Llvm/Types.hs
index e628fe6b1b..f1638ba5b6 100644
--- a/compiler/GHC/Llvm/Types.hs
+++ b/compiler/GHC/Llvm/Types.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE CPP        #-}
 {-# LANGUAGE LambdaCase #-}
 
 --------------------------------------------------------------------------------
diff --git a/compiler/GHC/Parser/Header.hs b/compiler/GHC/Parser/Header.hs
index 996c28449b..c4bc3f13da 100644
--- a/compiler/GHC/Parser/Header.hs
+++ b/compiler/GHC/Parser/Header.hs
@@ -1,5 +1,4 @@
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE CPP          #-}
 {-# LANGUAGE TypeFamilies #-}
 
 -----------------------------------------------------------------------------
diff --git a/compiler/GHC/Parser/PostProcess.hs b/compiler/GHC/Parser/PostProcess.hs
index 4294046d1f..ed11a4df18 100644
--- a/compiler/GHC/Parser/PostProcess.hs
+++ b/compiler/GHC/Parser/PostProcess.hs
@@ -1,23 +1,19 @@
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE FlexibleContexts  #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs             #-}
+{-# LANGUAGE RankNTypes        #-}
+{-# LANGUAGE TypeFamilies      #-}
+{-# LANGUAGE ViewPatterns      #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 --
 --  (c) The University of Glasgow 2002-2006
 --
 
 -- Functions over HsSyn specialised to RdrName.
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE MagicHash #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Parser.PostProcess (
         mkHsOpApp,
         mkHsIntegral, mkHsFractional, mkHsIsString,
diff --git a/compiler/GHC/Parser/PostProcess/Haddock.hs b/compiler/GHC/Parser/PostProcess/Haddock.hs
index 2caac6a446..849e2acdea 100644
--- a/compiler/GHC/Parser/PostProcess/Haddock.hs
+++ b/compiler/GHC/Parser/PostProcess/Haddock.hs
@@ -1,14 +1,13 @@
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE ApplicativeDo              #-}
+{-# LANGUAGE DeriveFunctor              #-}
+{-# LANGUAGE DerivingVia                #-}
+{-# LANGUAGE FlexibleInstances          #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE ApplicativeDo #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE DerivingVia #-}
-{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE NamedFieldPuns             #-}
+{-# LANGUAGE RankNTypes                 #-}
+{-# LANGUAGE ScopedTypeVariables        #-}
+{-# LANGUAGE TypeApplications           #-}
+{-# LANGUAGE TypeFamilies               #-}
 
 {- | This module implements 'addHaddockToModule', which inserts Haddock
     comments accumulated during parsing into the AST (#17544).
diff --git a/compiler/GHC/Rename/Doc.hs b/compiler/GHC/Rename/Doc.hs
new file mode 100644
index 0000000000..a01398b84f
--- /dev/null
+++ b/compiler/GHC/Rename/Doc.hs
@@ -0,0 +1,23 @@
+module GHC.Rename.Doc ( rnHsDoc, rnLHsDoc, rnMbLHsDoc ) where
+
+import GHC.Prelude
+
+import GHC.Tc.Types
+import GHC.Hs
+import GHC.Types.SrcLoc
+
+
+rnMbLHsDoc :: Maybe LHsDocString -> RnM (Maybe LHsDocString)
+rnMbLHsDoc mb_doc = case mb_doc of
+  Just doc -> do
+    doc' <- rnLHsDoc doc
+    return (Just doc')
+  Nothing -> return Nothing
+
+rnLHsDoc :: LHsDocString -> RnM LHsDocString
+rnLHsDoc (L pos doc) = do
+  doc' <- rnHsDoc doc
+  return (L pos doc')
+
+rnHsDoc :: HsDocString -> RnM HsDocString
+rnHsDoc = pure
diff --git a/compiler/GHC/Rename/Env.hs b/compiler/GHC/Rename/Env.hs
index 3344c7e3a1..0a1d7a08cd 100644
--- a/compiler/GHC/Rename/Env.hs
+++ b/compiler/GHC/Rename/Env.hs
@@ -1,3 +1,6 @@
+{-# LANGUAGE CPP            #-}
+{-# LANGUAGE NamedFieldPuns #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-2006
 
@@ -5,8 +8,6 @@ GHC.Rename.Env contains functions which convert RdrNames into Names.
 
 -}
 
-{-# LANGUAGE CPP, MultiWayIf, NamedFieldPuns #-}
-
 module GHC.Rename.Env (
         newTopSrcBinder,
         lookupLocatedTopBndrRn, lookupTopBndrRn,
diff --git a/compiler/GHC/Rename/Expr.hs b/compiler/GHC/Rename/Expr.hs
index eeecc5370f..1c0b425165 100644
--- a/compiler/GHC/Rename/Expr.hs
+++ b/compiler/GHC/Rename/Expr.hs
@@ -1,3 +1,12 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE MultiWayIf          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -10,16 +19,6 @@ general, all of these functions return a renamed thing, and a set of
 free variables.
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE MultiWayIf #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Rename.Expr (
         rnLExpr, rnExpr, rnStmts
    ) where
diff --git a/compiler/GHC/Rename/Fixity.hs b/compiler/GHC/Rename/Fixity.hs
index 89bc90e025..b3b195aa61 100644
--- a/compiler/GHC/Rename/Fixity.hs
+++ b/compiler/GHC/Rename/Fixity.hs
@@ -1,11 +1,8 @@
-{-# LANGUAGE ViewPatterns #-}
-
 {-
-
 This module contains code which maintains and manipulates the
 fixity environment during renaming.
-
 -}
+
 module GHC.Rename.Fixity
    ( MiniFixityEnv
    , addLocalFixities
@@ -13,8 +10,7 @@ module GHC.Rename.Fixity
    , lookupFixityRn_help
    , lookupFieldFixityRn
    , lookupTyFixityRn
-   )
-where
+   ) where
 
 import GHC.Prelude
 
diff --git a/compiler/GHC/Rename/HsType.hs b/compiler/GHC/Rename/HsType.hs
index 8d67aa1df2..999d7b3287 100644
--- a/compiler/GHC/Rename/HsType.hs
+++ b/compiler/GHC/Rename/HsType.hs
@@ -1,13 +1,12 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-
 module GHC.Rename.HsType (
         -- Type related stuff
         rnHsType, rnLHsType, rnLHsTypes, rnContext,
diff --git a/compiler/GHC/Rename/Module.hs b/compiler/GHC/Rename/Module.hs
index 7945263dc6..22b51ec30a 100644
--- a/compiler/GHC/Rename/Module.hs
+++ b/compiler/GHC/Rename/Module.hs
@@ -1,18 +1,17 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 Main pass of renamer
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Rename.Module (
         rnSrcDecls, addTcgDUs, findSplice
     ) where
diff --git a/compiler/GHC/Rename/Pat.hs b/compiler/GHC/Rename/Pat.hs
index 72058a2512..3a632c2705 100644
--- a/compiler/GHC/Rename/Pat.hs
+++ b/compiler/GHC/Rename/Pat.hs
@@ -1,3 +1,14 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DeriveFunctor       #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE RankNTypes          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE ViewPatterns        #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -9,18 +20,6 @@ Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes.  In
 general, all of these functions return a renamed thing, and a set of
 free variables.
 -}
-
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE DeriveFunctor #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Rename.Pat (-- main entry points
               rnPat, rnPats, rnBindPat, rnPatAndThen,
 
@@ -161,8 +160,8 @@ Consider
   g _ = T1
 
 Arguably we should report T2 as unused, even though it appears in a
-pattern, because it never occurs in a constructed position.  See
-#7336.
+pattern, because it never occurs in a constructed position.
+See #7336.
 However, implementing this in the face of pattern synonyms would be
 less straightforward, since given two pattern synonyms
 
diff --git a/compiler/GHC/Rename/Splice.hs b/compiler/GHC/Rename/Splice.hs
index cbbe38070c..b5bf6d22d7 100644
--- a/compiler/GHC/Rename/Splice.hs
+++ b/compiler/GHC/Rename/Splice.hs
@@ -1,6 +1,5 @@
-{-# LANGUAGE CPP #-}
+{-# LANGUAGE CPP          #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
diff --git a/compiler/GHC/Rename/Utils.hs b/compiler/GHC/Rename/Utils.hs
index 64b86e1e94..1b86fd9152 100644
--- a/compiler/GHC/Rename/Utils.hs
+++ b/compiler/GHC/Rename/Utils.hs
@@ -1,13 +1,12 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeFamilies     #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 {-
 
 This module contains miscellaneous functions related to renaming.
 
 -}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
 module GHC.Rename.Utils (
         checkDupRdrNames, checkShadowedRdrNames,
diff --git a/compiler/GHC/Runtime/Debugger.hs b/compiler/GHC/Runtime/Debugger.hs
index 9daa62d58d..3def133bea 100644
--- a/compiler/GHC/Runtime/Debugger.hs
+++ b/compiler/GHC/Runtime/Debugger.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE MagicHash #-}
-
 -----------------------------------------------------------------------------
 --
 -- GHCi Interactive debugging commands
diff --git a/compiler/GHC/Runtime/Loader.hs b/compiler/GHC/Runtime/Loader.hs
index b0a0c97c7b..be89d86192 100644
--- a/compiler/GHC/Runtime/Loader.hs
+++ b/compiler/GHC/Runtime/Loader.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, MagicHash #-}
+{-# LANGUAGE CPP #-}
 
 -- | Dynamically lookup up values from modules and loading them.
 module GHC.Runtime.Loader (
diff --git a/compiler/GHC/Stg/Lift/Analysis.hs b/compiler/GHC/Stg/Lift/Analysis.hs
index c0e4086f11..645616fde6 100644
--- a/compiler/GHC/Stg/Lift/Analysis.hs
+++ b/compiler/GHC/Stg/Lift/Analysis.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE DataKinds #-}
 
diff --git a/compiler/GHC/Stg/Lint.hs b/compiler/GHC/Stg/Lint.hs
index 2ce2c9b4d1..1485a11458 100644
--- a/compiler/GHC/Stg/Lint.hs
+++ b/compiler/GHC/Stg/Lint.hs
@@ -27,8 +27,8 @@ with this note:
     for Stg code that is currently perfectly acceptable for code
     generation.  Solution: don't use it!  (KSW 2000-05).
 
-Since then there were some attempts at enabling it again, as summarised in
-#14787. It's finally decided that we remove all type checking and only look for
+Since then there were some attempts at enabling it again, as summarised in #14787.
+It's finally decided that we remove all type checking and only look for
 basic properties listed above.
 -}
 
diff --git a/compiler/GHC/Stg/Syntax.hs b/compiler/GHC/Stg/Syntax.hs
index dcc9847ed4..b38c2f1ab0 100644
--- a/compiler/GHC/Stg/Syntax.hs
+++ b/compiler/GHC/Stg/Syntax.hs
@@ -1,3 +1,12 @@
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE ConstraintKinds      #-}
+{-# LANGUAGE DataKinds            #-}
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE LambdaCase           #-}
+{-# LANGUAGE TypeFamilies         #-}
+{-# LANGUAGE UndecidableInstances #-}
+
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
@@ -10,16 +19,6 @@ being one that happens to be ideally suited to spineless tagless code
 generation.
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE LambdaCase #-}
-
 module GHC.Stg.Syntax (
         StgArg(..),
 
diff --git a/compiler/GHC/Stg/Unarise.hs b/compiler/GHC/Stg/Unarise.hs
index 084c797136..eb4c968f5b 100644
--- a/compiler/GHC/Stg/Unarise.hs
+++ b/compiler/GHC/Stg/Unarise.hs
@@ -1,4 +1,8 @@
+{-# LANGUAGE CPP              #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TupleSections    #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
 {-
 (c) The GRASP/AQUA Project, Glasgow University, 1992-2012
@@ -194,10 +198,6 @@ STG programs after unarisation have these invariants:
   * Binders always have zero (for void arguments) or one PrimRep.
 -}
 
-{-# LANGUAGE CPP, TupleSections, PatternSynonyms #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.Stg.Unarise (unarise) where
 
 #include "HsVersions.h"
diff --git a/compiler/GHC/SysTools.hs b/compiler/GHC/SysTools.hs
index 0b649bc050..9e4a277957 100644
--- a/compiler/GHC/SysTools.hs
+++ b/compiler/GHC/SysTools.hs
@@ -1,3 +1,6 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
 {-
 -----------------------------------------------------------------------------
 --
@@ -8,8 +11,6 @@
 -----------------------------------------------------------------------------
 -}
 
-{-# LANGUAGE CPP, MultiWayIf, ScopedTypeVariables #-}
-
 module GHC.SysTools (
         -- * Initialisation
         initSysTools,
diff --git a/compiler/GHC/Tc/Deriv/Generics.hs b/compiler/GHC/Tc/Deriv/Generics.hs
index 9821d040e3..32567e1786 100644
--- a/compiler/GHC/Tc/Deriv/Generics.hs
+++ b/compiler/GHC/Tc/Deriv/Generics.hs
@@ -1,14 +1,15 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2011
 
 -}
 
-{-# LANGUAGE CPP, ScopedTypeVariables, TupleSections #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 -- | The deriving code for the Generic class
 module GHC.Tc.Deriv.Generics
    (canDoGenerics
diff --git a/compiler/GHC/Tc/Deriv/Infer.hs b/compiler/GHC/Tc/Deriv/Infer.hs
index fb038b23fb..eb81587eb7 100644
--- a/compiler/GHC/Tc/Deriv/Infer.hs
+++ b/compiler/GHC/Tc/Deriv/Infer.hs
@@ -464,8 +464,7 @@ and them simplify them in simplifyInstanceContexts; see
 Note [Simplifying the instance context].
 
 In the functor-like case, we may need to unify some kind variables with * in
-order for the generated instance to be well-kinded. An example from
-#10524:
+order for the generated instance to be well-kinded. An example from #10524:
 
   newtype Compose (f :: k2 -> *) (g :: k1 -> k2) (a :: k1)
     = Compose (f (g a)) deriving Functor
diff --git a/compiler/GHC/Tc/Deriv/Utils.hs b/compiler/GHC/Tc/Deriv/Utils.hs
index e14d1ca7d8..36d6293941 100644
--- a/compiler/GHC/Tc/Deriv/Utils.hs
+++ b/compiler/GHC/Tc/Deriv/Utils.hs
@@ -1113,8 +1113,7 @@ example of this is:
     data T a b = C (Show a) b => MkT b
 
 Here, the existential context (C (Show a) b) does technically mention the last
-type variable b. But this is OK, because expanding the type synonym C would
-give us the context (Show a), which doesn't mention b. Therefore, we must make
-sure to expand type synonyms before performing this check. Not doing so led to
-#13813.
+type variable b. But this is OK, because expanding the type synonym C would give
+us the context (Show a), which doesn't mention b. Therefore, we must make sure
+to expand type synonyms before performing this check. Not doing so led to #13813.
 -}
diff --git a/compiler/GHC/Tc/Errors.hs b/compiler/GHC/Tc/Errors.hs
index 93c047ca32..8b50d5e719 100644
--- a/compiler/GHC/Tc/Errors.hs
+++ b/compiler/GHC/Tc/Errors.hs
@@ -1,7 +1,6 @@
-{-# LANGUAGE CPP #-}
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE LambdaCase          #-}
 {-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE LambdaCase #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
diff --git a/compiler/GHC/Tc/Gen/App.hs b/compiler/GHC/Tc/Gen/App.hs
index 13b92a43c2..ab8c3c7247 100644
--- a/compiler/GHC/Tc/Gen/App.hs
+++ b/compiler/GHC/Tc/Gen/App.hs
@@ -1,16 +1,19 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE GADTs               #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 %
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
 
-{-# LANGUAGE CPP, TupleSections, ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies, DataKinds, GADTs, TypeApplications #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Tc.Gen.App
        ( tcApp
        , tcInferSigma
@@ -645,8 +648,8 @@ Note [Visible type application zonk]
   (checkExpectedKind zonks as it goes).
 
 So we must zonk inner_ty as well, to guarantee consistency between zonk(tv)
-and inner_ty.  Otherwise we can build an ill-kinded type.  An example was
-#14158, where we had:
+and inner_ty. Otherwise we can build an ill-kinded type. An example was #14158,
+where we had:
    id :: forall k. forall (cat :: k -> k -> *). forall (a :: k). cat a a
 and we had the visible type application
   id @(->)
diff --git a/compiler/GHC/Tc/Gen/Arrow.hs b/compiler/GHC/Tc/Gen/Arrow.hs
index 82d405f0bb..ed30afa893 100644
--- a/compiler/GHC/Tc/Gen/Arrow.hs
+++ b/compiler/GHC/Tc/Gen/Arrow.hs
@@ -1,14 +1,14 @@
+{-# LANGUAGE RankNTypes    #-}
+{-# LANGUAGE TypeFamilies  #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE RankNTypes, TupleSections #-}
-{-# LANGUAGE TypeFamilies #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Typecheck arrow notation
 module GHC.Tc.Gen.Arrow ( tcProc ) where
 
diff --git a/compiler/GHC/Tc/Gen/Bind.hs b/compiler/GHC/Tc/Gen/Bind.hs
index f2a810dbca..03ce1353a0 100644
--- a/compiler/GHC/Tc/Gen/Bind.hs
+++ b/compiler/GHC/Tc/Gen/Bind.hs
@@ -1,14 +1,15 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE RankNTypes          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP, RankNTypes, ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
 module GHC.Tc.Gen.Bind
    ( tcLocalBinds
    , tcTopBinds
diff --git a/compiler/GHC/Tc/Gen/Export.hs b/compiler/GHC/Tc/Gen/Export.hs
index ec4475edea..9b503da19c 100644
--- a/compiler/GHC/Tc/Gen/Export.hs
+++ b/compiler/GHC/Tc/Gen/Export.hs
@@ -1,9 +1,7 @@
-{-# LANGUAGE NamedFieldPuns #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE FlexibleContexts  #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE RankNTypes        #-}
+{-# LANGUAGE TypeFamilies      #-}
 
 module GHC.Tc.Gen.Export (tcRnExports, exports_from_avail) where
 
diff --git a/compiler/GHC/Tc/Gen/Expr.hs b/compiler/GHC/Tc/Gen/Expr.hs
index 3b4aa4ec20..a64154facf 100644
--- a/compiler/GHC/Tc/Gen/Expr.hs
+++ b/compiler/GHC/Tc/Gen/Expr.hs
@@ -1,3 +1,13 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TupleSections       #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+                                      -- in module GHC.Hs.Extension
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 %
 (c) The University of Glasgow 2006
@@ -5,14 +15,6 @@
 
 -}
 
-{-# LANGUAGE CPP, TupleSections, ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies, DataKinds, TypeApplications #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-                                      -- in module GHC.Hs.Extension
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Tc.Gen.Expr
        ( tcCheckPolyExpr, tcCheckPolyExprNC,
          tcCheckMonoExpr, tcCheckMonoExprNC, tcMonoExpr, tcMonoExprNC,
diff --git a/compiler/GHC/Tc/Gen/Head.hs b/compiler/GHC/Tc/Gen/Head.hs
index 50ff9508ca..312962a889 100644
--- a/compiler/GHC/Tc/Gen/Head.hs
+++ b/compiler/GHC/Tc/Gen/Head.hs
@@ -1,16 +1,20 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE GADTs               #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TupleSections       #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 %
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
 
-{-# LANGUAGE CPP, TupleSections, ScopedTypeVariables #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies, DataKinds, GADTs, TypeApplications #-}
-{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Tc.Gen.Head
        ( HsExprArg(..), EValArg(..), TcPass(..), Rebuilder
        , splitHsApps
@@ -1089,8 +1093,8 @@ this by checking if the type of the applied function has more argument types
 than supplied arguments.
 
 Previously, GHC computed the number of argument types through tcSplitSigmaTy.
-This is incorrect in the face of nested foralls, however! This caused Trac
-#13311, for instance:
+This is incorrect in the face of nested foralls, however!
+This caused Ticket #13311, for instance:
 
   f :: forall a. (Monoid a) => forall b. (Monoid b) => Maybe a -> Maybe b
 
diff --git a/compiler/GHC/Tc/Gen/HsType.hs b/compiler/GHC/Tc/Gen/HsType.hs
index d23c09fd09..324bdca5bf 100644
--- a/compiler/GHC/Tc/Gen/HsType.hs
+++ b/compiler/GHC/Tc/Gen/HsType.hs
@@ -1,17 +1,17 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE RankNTypes          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies        #-}
+{-# LANGUAGE ViewPatterns        #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP, TupleSections, MultiWayIf, RankNTypes #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 -- | Typechecking user-specified @MonoTypes@
 module GHC.Tc.Gen.HsType (
         -- Type signatures
@@ -1905,12 +1905,12 @@ Note [Recursion through the kinds]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Consider these examples
 
-#11554:
+Ticket #11554:
   data P (x :: k) = Q
   data A :: Type where
     MkA :: forall (a :: A). P a -> A
 
-#12174
+Ticket #12174
   data V a
   data T = forall (a :: T). MkT (V a)
 
diff --git a/compiler/GHC/Tc/Gen/Match.hs b/compiler/GHC/Tc/Gen/Match.hs
index 38e400419a..ff01093a34 100644
--- a/compiler/GHC/Tc/Gen/Match.hs
+++ b/compiler/GHC/Tc/Gen/Match.hs
@@ -1,19 +1,18 @@
+{-# LANGUAGE CPP              #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE RankNTypes       #-}
+{-# LANGUAGE RecordWildCards  #-}
+{-# LANGUAGE TupleSections    #-}
+{-# LANGUAGE TypeFamilies     #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE MultiWayIf #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE RecordWildCards #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 -- | Typecheck some @Matches@
 module GHC.Tc.Gen.Match
    ( tcMatchesFun
diff --git a/compiler/GHC/Tc/Gen/Pat.hs b/compiler/GHC/Tc/Gen/Pat.hs
index 27b2b1358b..4ee4480c60 100644
--- a/compiler/GHC/Tc/Gen/Pat.hs
+++ b/compiler/GHC/Tc/Gen/Pat.hs
@@ -1,18 +1,17 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-
--}
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TupleSections #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+
+-}
+
 -- | Typechecking patterns
 module GHC.Tc.Gen.Pat
    ( tcLetPat
diff --git a/compiler/GHC/Tc/Gen/Rule.hs b/compiler/GHC/Tc/Gen/Rule.hs
index 5ee65b6e05..ec9d1da5e9 100644
--- a/compiler/GHC/Tc/Gen/Rule.hs
+++ b/compiler/GHC/Tc/Gen/Rule.hs
@@ -1,12 +1,11 @@
+{-# LANGUAGE TypeFamilies #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The AQUA Project, Glasgow University, 1993-1998
 
 -}
 
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE TypeFamilies #-}
-
 -- | Typechecking rewrite rules
 module GHC.Tc.Gen.Rule ( tcRules ) where
 
diff --git a/compiler/GHC/Tc/Gen/Splice.hs b/compiler/GHC/Tc/Gen/Splice.hs
index 54e736fda5..c83890b1ae 100644
--- a/compiler/GHC/Tc/Gen/Splice.hs
+++ b/compiler/GHC/Tc/Gen/Splice.hs
@@ -1,26 +1,22 @@
+{-# LANGUAGE CPP                    #-}
+{-# LANGUAGE FlexibleInstances      #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE GADTs                  #-}
+{-# LANGUAGE InstanceSigs           #-}
+{-# LANGUAGE MultiWayIf             #-}
+{-# LANGUAGE ScopedTypeVariables    #-}
+{-# LANGUAGE TupleSections          #-}
+{-# LANGUAGE TypeFamilies           #-}
+
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MagicHash #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE InstanceSigs #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE MultiWayIf #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE FunctionalDependencies #-}
-{-# OPTIONS_GHC -fno-warn-orphans #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 -- | Template Haskell splices
 module GHC.Tc.Gen.Splice(
      tcSpliceExpr, tcTypedBracket, tcUntypedBracket,
@@ -573,8 +569,8 @@ For correct pattern-match warnings it's crucial that we annotate the Origin
 consistently (#17270). In the future we could offer the Origin as part of the
 TH AST. That would enable us to give quotes from the current module get
 FromSource origin, and/or third library authors to tag certain parts of
-generated code as FromSource to enable warnings. That effort is tracked in
-#14838.
+generated code as FromSource to enable warnings.
+That effort is tracked in #14838.
 -}
 
 {-
diff --git a/compiler/GHC/Tc/Module.hs b/compiler/GHC/Tc/Module.hs
index b83a4bee8e..2b583cd6a4 100644
--- a/compiler/GHC/Tc/Module.hs
+++ b/compiler/GHC/Tc/Module.hs
@@ -1,21 +1,19 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-
--}
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE NondecreasingIndentation #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+
+-}
+
 -- | Typechecking a whole module
 --
 -- https://gitlab.haskell.org/ghc/ghc/wikis/commentary/compiler/type-checker
diff --git a/compiler/GHC/Tc/Solver.hs b/compiler/GHC/Tc/Solver.hs
index 70af1b1255..ab1e6d56d3 100644
--- a/compiler/GHC/Tc/Solver.hs
+++ b/compiler/GHC/Tc/Solver.hs
@@ -2317,8 +2317,7 @@ But this transitive closure stuff gives rise to a complex rule for
 when defaulting actually happens, and one that was never documented.
 Moreover (#12923), the more complex rule is sometimes NOT what
 you want.  So I simply removed the extra code to implement the
-contamination stuff.  There was zero effect on the testsuite (not even
-#8155).
+contamination stuff.  There was zero effect on the testsuite (not even #8155).
 ------ End of historical note -----------
 
 
diff --git a/compiler/GHC/Tc/Solver/Flatten.hs b/compiler/GHC/Tc/Solver/Flatten.hs
index 2a4c7be1bb..dd214ceb7c 100644
--- a/compiler/GHC/Tc/Solver/Flatten.hs
+++ b/compiler/GHC/Tc/Solver/Flatten.hs
@@ -1,4 +1,6 @@
-{-# LANGUAGE CPP, DeriveFunctor, ViewPatterns, BangPatterns #-}
+{-# LANGUAGE BangPatterns  #-}
+{-# LANGUAGE CPP           #-}
+{-# LANGUAGE DeriveFunctor #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
diff --git a/compiler/GHC/Tc/Solver/Interact.hs b/compiler/GHC/Tc/Solver/Interact.hs
index 57bca5fcec..fe349866d2 100644
--- a/compiler/GHC/Tc/Solver/Interact.hs
+++ b/compiler/GHC/Tc/Solver/Interact.hs
@@ -939,7 +939,7 @@ can change the behavior of the user's code.
 The following four modules produce a program whose output would change depending
 on whether we apply this optimization when IncoherentInstances is in effect:
 
-#########
+=========
     {-# LANGUAGE MultiParamTypeClasses #-}
     module A where
 
@@ -949,8 +949,9 @@ on whether we apply this optimization when IncoherentInstances is in effect:
     class A a => C a b where
       m :: b -> a -> a
 
-#########
-    {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-}
+=========
+    {-# LANGUAGE FlexibleInstances     #-}
+    {-# LANGUAGE MultiParamTypeClasses #-}
     module B where
 
     import A
@@ -961,9 +962,11 @@ on whether we apply this optimization when IncoherentInstances is in effect:
     instance C a [b] where
       m _ = id
 
-#########
-    {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, FlexibleContexts #-}
-    {-# LANGUAGE IncoherentInstances #-}
+=========
+    {-# LANGUAGE FlexibleContexts      #-}
+    {-# LANGUAGE FlexibleInstances     #-}
+    {-# LANGUAGE IncoherentInstances   #-}
+    {-# LANGUAGE MultiParamTypeClasses #-}
     module C where
 
     import A
@@ -977,7 +980,7 @@ on whether we apply this optimization when IncoherentInstances is in effect:
     intC :: C Int a => a -> Int -> Int
     intC _ x = int x
 
-#########
+=========
     module Main where
 
     import A
diff --git a/compiler/GHC/Tc/Solver/Monad.hs b/compiler/GHC/Tc/Solver/Monad.hs
index a524493b94..4c20eed977 100644
--- a/compiler/GHC/Tc/Solver/Monad.hs
+++ b/compiler/GHC/Tc/Solver/Monad.hs
@@ -1300,7 +1300,7 @@ This is triggered by test case typecheck/should_compile/SplitWD.
 
 Note [Examples of how Derived shadows helps completeness]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-#10009, a very nasty example:
+Ticket #10009, a very nasty example:
 
     f :: (UnF (F b) ~ b) => F b -> ()
 
diff --git a/compiler/GHC/Tc/TyCl/PatSyn.hs b/compiler/GHC/Tc/TyCl/PatSyn.hs
index 88a0e4eeef..79d3f97077 100644
--- a/compiler/GHC/Tc/TyCl/PatSyn.hs
+++ b/compiler/GHC/Tc/TyCl/PatSyn.hs
@@ -1,16 +1,15 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-
--}
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+
+-}
+
 -- | Typechecking pattern synonym declarations
 module GHC.Tc.TyCl.PatSyn
    ( tcPatSynDecl
diff --git a/compiler/GHC/Tc/TyCl/Utils.hs b/compiler/GHC/Tc/TyCl/Utils.hs
index 031faebed0..a225fbdd6d 100644
--- a/compiler/GHC/Tc/TyCl/Utils.hs
+++ b/compiler/GHC/Tc/TyCl/Utils.hs
@@ -1,16 +1,15 @@
-{-
-(c) The University of Glasgow 2006
-(c) The GRASP/AQUA Project, Glasgow University, 1992-1999
-
--}
-
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
 
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1992-1999
+
+-}
+
 -- | Analysis functions over data types. Specifically, detecting recursive types.
 --
 -- This stuff is only used for source-code decls; it's recorded in interface
diff --git a/compiler/GHC/Tc/Types.hs b/compiler/GHC/Tc/Types.hs
index 884e72f899..24b4905399 100644
--- a/compiler/GHC/Tc/Types.hs
+++ b/compiler/GHC/Tc/Types.hs
@@ -1,12 +1,14 @@
+{-# LANGUAGE CPP                        #-}
+{-# LANGUAGE DeriveFunctor              #-}
+{-# LANGUAGE ExistentialQuantification  #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+
 {-
 (c) The University of Glasgow 2006-2012
 (c) The GRASP Project, Glasgow University, 1992-2002
 
 -}
 
-{-# LANGUAGE CPP, DeriveFunctor, ExistentialQuantification, GeneralizedNewtypeDeriving,
-             ViewPatterns #-}
-
 -- | Various types used during typechecking.
 --
 -- Please see "GHC.Tc.Utils.Monad" as well for operations on these types. You probably
diff --git a/compiler/GHC/Tc/Utils/Backpack.hs b/compiler/GHC/Tc/Utils/Backpack.hs
index dcdf51c237..7919f8cc4c 100644
--- a/compiler/GHC/Tc/Utils/Backpack.hs
+++ b/compiler/GHC/Tc/Utils/Backpack.hs
@@ -1,9 +1,7 @@
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE CPP                      #-}
 {-# LANGUAGE NondecreasingIndentation #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE ScopedTypeVariables      #-}
+{-# LANGUAGE TypeFamilies             #-}
 
 module GHC.Tc.Utils.Backpack (
     findExtraSigImports',
diff --git a/compiler/GHC/Tc/Utils/Instantiate.hs b/compiler/GHC/Tc/Utils/Instantiate.hs
index 0e928ed5fd..a47e913d17 100644
--- a/compiler/GHC/Tc/Utils/Instantiate.hs
+++ b/compiler/GHC/Tc/Utils/Instantiate.hs
@@ -1,15 +1,15 @@
+{-# LANGUAGE CPP              #-}
+{-# LANGUAGE FlexibleContexts #-}
+
+{-# 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
 
 -}
 
-{-# LANGUAGE CPP, MultiWayIf, TupleSections #-}
-{-# LANGUAGE FlexibleContexts #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 module GHC.Tc.Utils.Instantiate (
        topSkolemise,
        topInstantiate, instantiateSigma,
diff --git a/compiler/GHC/Tc/Utils/Monad.hs b/compiler/GHC/Tc/Utils/Monad.hs
index 7932d140b3..9910101424 100644
--- a/compiler/GHC/Tc/Utils/Monad.hs
+++ b/compiler/GHC/Tc/Utils/Monad.hs
@@ -1,14 +1,16 @@
-{-
-(c) The University of Glasgow 2006
-
--}
+{-# LANGUAGE BangPatterns      #-}
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE ExplicitForAll    #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE RecordWildCards   #-}
 
-{-# LANGUAGE CPP, ExplicitForAll, FlexibleInstances, BangPatterns #-}
-{-# LANGUAGE RecordWildCards #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# LANGUAGE ViewPatterns #-}
 
+{-
+(c) The University of Glasgow 2006
+
+-}
 
 -- | Functions for working with the typechecker environment (setters,
 -- getters...).
diff --git a/compiler/GHC/Tc/Utils/TcMType.hs b/compiler/GHC/Tc/Utils/TcMType.hs
index 88c354fd80..2d2430e7d9 100644
--- a/compiler/GHC/Tc/Utils/TcMType.hs
+++ b/compiler/GHC/Tc/Utils/TcMType.hs
@@ -1,13 +1,14 @@
+{-# LANGUAGE CPP             #-}
+{-# LANGUAGE MultiWayIf      #-}
+{-# LANGUAGE TupleSections   #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP, TupleSections, MultiWayIf, PatternSynonyms, BangPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Monadic type operations
 --
 -- This module contains monadic operations over types that contain mutable type
diff --git a/compiler/GHC/Tc/Utils/TcType.hs b/compiler/GHC/Tc/Utils/TcType.hs
index 6d5ef37442..54258c7e52 100644
--- a/compiler/GHC/Tc/Utils/TcType.hs
+++ b/compiler/GHC/Tc/Utils/TcType.hs
@@ -1,12 +1,15 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 
 -}
 
-{-# LANGUAGE CPP, ScopedTypeVariables, MultiWayIf, FlexibleContexts #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Types used in the typechecker
 --
 -- This module provides the Type interface for front-end parts of the
diff --git a/compiler/GHC/Tc/Utils/Unify.hs b/compiler/GHC/Tc/Utils/Unify.hs
index 0c29a6557f..c1202f02d7 100644
--- a/compiler/GHC/Tc/Utils/Unify.hs
+++ b/compiler/GHC/Tc/Utils/Unify.hs
@@ -1,15 +1,16 @@
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DeriveFunctor       #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TupleSections       #-}
+
+{-# 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
-
 -}
 
-{-# LANGUAGE CPP, DeriveFunctor, MultiWayIf, TupleSections,
-    ScopedTypeVariables #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Type subsumption and unification
 module GHC.Tc.Utils.Unify (
   -- Full-blown subsumption
diff --git a/compiler/GHC/Tc/Utils/Zonk.hs b/compiler/GHC/Tc/Utils/Zonk.hs
index e00b5a09e3..a47b75adc2 100644
--- a/compiler/GHC/Tc/Utils/Zonk.hs
+++ b/compiler/GHC/Tc/Utils/Zonk.hs
@@ -1,16 +1,15 @@
+{-# LANGUAGE CPP              #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeFamilies     #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The AQUA Project, Glasgow University, 1996-1998
 
 -}
 
-{-# LANGUAGE CPP, TupleSections #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-
 -- | Specialisations of the @HsSyn@ syntax for the typechecker
 --
 -- This module is an extension of @HsSyn@ syntax, for use in the type checker.
diff --git a/compiler/GHC/Tc/Validity.hs b/compiler/GHC/Tc/Validity.hs
index 540480147c..5f08249e38 100644
--- a/compiler/GHC/Tc/Validity.hs
+++ b/compiler/GHC/Tc/Validity.hs
@@ -1,13 +1,13 @@
+{-# LANGUAGE CPP           #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 -}
 
-{-# LANGUAGE CPP, TupleSections, ViewPatterns #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.Tc.Validity (
   Rank, UserTypeCtxt(..), checkValidType, checkValidMonoType,
   checkValidTheta,
diff --git a/compiler/GHC/ThToHs.hs b/compiler/GHC/ThToHs.hs
index 450e231628..3f093dd8b8 100644
--- a/compiler/GHC/ThToHs.hs
+++ b/compiler/GHC/ThToHs.hs
@@ -1,3 +1,16 @@
+{-# LANGUAGE BangPatterns            #-}
+{-# LANGUAGE DeriveFunctor           #-}
+{-# LANGUAGE FlexibleContexts        #-}
+{-# LANGUAGE FunctionalDependencies  #-}
+{-# LANGUAGE LambdaCase              #-}
+{-# LANGUAGE ConstrainedClassMethods #-}
+{-# LANGUAGE ScopedTypeVariables     #-}
+{-# LANGUAGE TypeFamilies            #-}
+{-# LANGUAGE ViewPatterns            #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -6,19 +19,6 @@
 This module converts Template Haskell syntax into Hs syntax
 -}
 
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE LambdaCase #-}
-
-{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns   #-}
-
 module GHC.ThToHs
    ( convertToHsExpr
    , convertToPat
diff --git a/compiler/GHC/Types/Demand.hs b/compiler/GHC/Types/Demand.hs
index ec008ab07c..ac1a14d818 100644
--- a/compiler/GHC/Types/Demand.hs
+++ b/compiler/GHC/Types/Demand.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP                  #-}
+{-# LANGUAGE FlexibleInstances    #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -5,9 +10,6 @@
 \section[Demand]{@Demand@: A decoupled implementation of a demand domain}
 -}
 
-{-# LANGUAGE CPP, FlexibleInstances, TypeSynonymInstances, RecordWildCards #-}
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 module GHC.Types.Demand (
         StrDmd, UseDmd(..), Count,
 
diff --git a/compiler/GHC/Types/FieldLabel.hs b/compiler/GHC/Types/FieldLabel.hs
index 7636545963..f3352c50a1 100644
--- a/compiler/GHC/Types/FieldLabel.hs
+++ b/compiler/GHC/Types/FieldLabel.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveTraversable  #-}
+{-# LANGUAGE StandaloneDeriving #-}
+
 {-
 %
 % (c) Adam Gundry 2013-2015
@@ -56,12 +60,6 @@ Of course, datatypes with no constructors cannot have any fields.
 
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE DeriveFoldable #-}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE StandaloneDeriving #-}
-
 module GHC.Types.FieldLabel
    ( FieldLabelString
    , FieldLabelEnv
diff --git a/compiler/GHC/Types/Name.hs b/compiler/GHC/Types/Name.hs
index 6cdf6513d6..fa38678896 100644
--- a/compiler/GHC/Types/Name.hs
+++ b/compiler/GHC/Types/Name.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE RecordWildCards   #-}
+{-# LANGUAGE TypeFamilies      #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -5,11 +9,6 @@
 \section[Name]{@Name@: to transmit name info from renamer to typechecker}
 -}
 
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE PatternSynonyms #-}
-
 -- |
 -- #name_types#
 -- GHC uses several kinds of name internally:
diff --git a/compiler/GHC/Types/SrcLoc.hs b/compiler/GHC/Types/SrcLoc.hs
index 30db87d827..38c7872358 100644
--- a/compiler/GHC/Types/SrcLoc.hs
+++ b/compiler/GHC/Types/SrcLoc.hs
@@ -1,17 +1,11 @@
--- (c) The University of Glasgow, 1992-2006
-
 {-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE DeriveFunctor      #-}
-{-# LANGUAGE DeriveFoldable     #-}
 {-# LANGUAGE DeriveTraversable  #-}
+{-# LANGUAGE FlexibleContexts   #-}
 {-# LANGUAGE FlexibleInstances  #-}
 {-# LANGUAGE RecordWildCards    #-}
 {-# LANGUAGE TypeFamilies       #-}
-{-# LANGUAGE ViewPatterns       #-}
-{-# LANGUAGE FlexibleContexts   #-}
-{-# LANGUAGE PatternSynonyms    #-}
 
+-- (c) The University of Glasgow, 1992-2006
 
 -- | This module contains types that relate to the positions of things
 -- in source files, and allow tagging of those things with locations
diff --git a/compiler/GHC/Unit.hs b/compiler/GHC/Unit.hs
index 64577d55ae..593e94fa38 100644
--- a/compiler/GHC/Unit.hs
+++ b/compiler/GHC/Unit.hs
@@ -1,6 +1,4 @@
-{-# LANGUAGE TypeSynonymInstances #-}
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE DeriveFunctor #-}
 
 -- | Units are library components from Cabal packages compiled and installed in
 -- a database
diff --git a/compiler/GHC/Unit/Module.hs b/compiler/GHC/Unit/Module.hs
index cb8e6c3fe9..6431aaeae2 100644
--- a/compiler/GHC/Unit/Module.hs
+++ b/compiler/GHC/Unit/Module.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE ExplicitNamespaces #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE RecordWildCards #-}
+
 {-
 (c) The University of Glasgow, 2004-2006
 
@@ -9,14 +14,6 @@ These are Uniquable, hence we can build Maps with Modules as
 the keys.
 -}
 
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE ExplicitNamespaces #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-
 module GHC.Unit.Module
     ( module GHC.Unit.Types
 
diff --git a/compiler/GHC/Utils/Error.hs b/compiler/GHC/Utils/Error.hs
index 72b469f7d3..1bd3e57f56 100644
--- a/compiler/GHC/Utils/Error.hs
+++ b/compiler/GHC/Utils/Error.hs
@@ -1,15 +1,14 @@
+{-# LANGUAGE BangPatterns    #-}
+{-# LANGUAGE CPP             #-}
+{-# LANGUAGE LambdaCase      #-}
+{-# LANGUAGE RankNTypes      #-}
+
 {-
 (c) The AQUA Project, Glasgow University, 1994-1998
 
 \section[ErrsUtils]{Utilities for error reporting}
 -}
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE LambdaCase #-}
-
 module GHC.Utils.Error (
         -- * Basic types
         Validity(..), andValid, allValid, isValid, getInvalids, orValid,
diff --git a/hadrian/src/Main.hs b/hadrian/src/Main.hs
index e6bf015c0a..d75bc743a7 100644
--- a/hadrian/src/Main.hs
+++ b/hadrian/src/Main.hs
@@ -1,21 +1,21 @@
 module Main (main) where
 
-import System.Directory (getCurrentDirectory)
 import Development.Shake
 import Hadrian.Expression
 import Hadrian.Utilities
 import Settings.Parser
+import System.Directory (getCurrentDirectory)
 
 import qualified Base
 import qualified CommandLine
 import qualified Environment
 import qualified Rules
 import qualified Rules.Clean
-import qualified Rules.Lint
 import qualified Rules.Documentation
+import qualified Rules.Lint
 import qualified Rules.Nofib
-import qualified Rules.SourceDist
 import qualified Rules.Selftest
+import qualified Rules.SourceDist
 import qualified Rules.Test
 import qualified UserSettings
 
diff --git a/hadrian/src/Rules/Lint.hs b/hadrian/src/Rules/Lint.hs
index 39e047a4d4..76ee4a7028 100644
--- a/hadrian/src/Rules/Lint.hs
+++ b/hadrian/src/Rules/Lint.hs
@@ -7,7 +7,9 @@ import Settings.Builders.Common
 import System.Directory (findExecutable)
 
 lintRules :: Rules ()
-lintRules = "lint:base" ~> lint base
+lintRules = do
+  "lint:base" ~> lint base
+  "lint:compiler" ~> lint compiler
 
 lint :: Action () -> Action ()
 lint lintAction = do
@@ -43,3 +45,31 @@ base = do
                 " -h " <> hlintYaml <> " libraries/base"
   putBuild $ "| " <> cmdLine
   cmd_ cmdLine
+
+compiler :: Action ()
+compiler = do
+  topDir   <- topDirectory
+  buildDir <- buildRoot
+  let stage1Lib      = topDir </> buildDir </> "stage1/lib"
+  let stage1Compiler = topDir </> buildDir </> "stage1/compiler/build"
+  let machDeps       = topDir </> "includes/MachDeps.h"
+  let hsVersions     = topDir </> "compiler/HsVersions.h"
+  let compilerDir    = topDir </> "compiler"
+  let ghcautoconf    = stage1Lib </> "ghcautoconf.h"
+  let ghcplatform    = stage1Lib </> "ghcplatform.h"
+  let pmv            = stage1Compiler </> "primop-vector-uniques.hs-incl"
+  need [ghcautoconf, ghcplatform, machDeps, hsVersions, pmv]
+  let include0  = topDir </> "includes"
+  let include1  = stage1Lib
+  let hlintYaml = topDir </> "compiler/.hlint.yaml"
+  hostArch <- (<> "_HOST_ARCH") <$> setting HostArch
+  let cmdLine = "hlint -j --cpp-define " <> hostArch <>
+                " --cpp-include=" <> include0 <>
+                " --cpp-include=" <> include1 <>
+                " --cpp-include=" <> compilerDir <>
+                " --cpp-include=" <> ghcplatform <>
+                " --cpp-include=" <> stage1Compiler <>
+                " -h " <> hlintYaml <> " compiler"
+  putBuild $ "| " <> cmdLine
+  cmd_ cmdLine
+