Remove unused imports of the form 'import foo ()' (Fixes #17065)

These kinds of imports are necessary in some cases such as
importing instances of typeclasses or intentionally creating
dependencies in the build system, but '-Wunused-imports' can't
detect when they are no longer needed. This commit removes the
unused ones currently in the code base (not including test files
or submodules), with the hope that doing so may increase
parallelism in the build system by removing unnecessary
dependencies.

35 files changed, 14 insertions, 40 deletions

diff --git a/compiler/cmm/CmmBuildInfoTables.hs b/compiler/cmm/CmmBuildInfoTables.hs
index 90d15aeea7..9c05a8fe29 100644
--- a/compiler/cmm/CmmBuildInfoTables.hs
+++ b/compiler/cmm/CmmBuildInfoTables.hs
@@ -19,7 +19,6 @@ import Module
 import GHC.Platform
 import Digraph
 import CLabel
-import PprCmmDecl ()
 import Cmm
 import CmmUtils
 import DynFlags
@@ -30,7 +29,6 @@ import UniqSupply
 import CostCentre
 import StgCmmHeap
 
-import PprCmm()
 import Control.Monad
 import Data.Map (Map)
 import qualified Data.Map as Map
diff --git a/compiler/cmm/CmmCallConv.hs b/compiler/cmm/CmmCallConv.hs
index 4e6a9d293a..df1eaad005 100644
--- a/compiler/cmm/CmmCallConv.hs
+++ b/compiler/cmm/CmmCallConv.hs
@@ -10,7 +10,7 @@ import GhcPrelude
 import CmmExpr
 import SMRep
 import Cmm (Convention(..))
-import PprCmm ()
+import PprCmm () -- For Outputable instances
 
 import DynFlags
 import GHC.Platform
diff --git a/compiler/cmm/CmmCommonBlockElim.hs b/compiler/cmm/CmmCommonBlockElim.hs
index b43d68970f..cbf7d83d36 100644
--- a/compiler/cmm/CmmCommonBlockElim.hs
+++ b/compiler/cmm/CmmCommonBlockElim.hs
@@ -13,7 +13,6 @@ import Cmm
 import CmmUtils
 import CmmSwitch (eqSwitchTargetWith)
 import CmmContFlowOpt
--- import PprCmm ()
 
 import Hoopl.Block
 import Hoopl.Graph
diff --git a/compiler/cmm/CmmLint.hs b/compiler/cmm/CmmLint.hs
index d5c3f84443..3ad65bd536 100644
--- a/compiler/cmm/CmmLint.hs
+++ b/compiler/cmm/CmmLint.hs
@@ -21,7 +21,7 @@ import Cmm
 import CmmUtils
 import CmmLive
 import CmmSwitch (switchTargetsToList)
-import PprCmm ()
+import PprCmm () -- For Outputable instances
 import Outputable
 import DynFlags
 
diff --git a/compiler/cmm/CmmLive.hs b/compiler/cmm/CmmLive.hs
index f340c32c8a..ca474ef61c 100644
--- a/compiler/cmm/CmmLive.hs
+++ b/compiler/cmm/CmmLive.hs
@@ -17,7 +17,7 @@ import GhcPrelude
 import DynFlags
 import BlockId
 import Cmm
-import PprCmmExpr ()
+import PprCmmExpr () -- For Outputable instances
 import Hoopl.Block
 import Hoopl.Collections
 import Hoopl.Dataflow
diff --git a/compiler/cmm/CmmProcPoint.hs b/compiler/cmm/CmmProcPoint.hs
index 528337c57e..746a175cfe 100644
--- a/compiler/cmm/CmmProcPoint.hs
+++ b/compiler/cmm/CmmProcPoint.hs
@@ -14,7 +14,7 @@ import DynFlags
 import BlockId
 import CLabel
 import Cmm
-import PprCmm ()
+import PprCmm () -- For Outputable instances
 import CmmUtils
 import CmmInfo
 import CmmLive
diff --git a/compiler/cmm/CmmSink.hs b/compiler/cmm/CmmSink.hs
index 409cd0fbf2..8a6b120377 100644
--- a/compiler/cmm/CmmSink.hs
+++ b/compiler/cmm/CmmSink.hs
@@ -19,7 +19,6 @@ import GHC.Platform (isARM, platformArch)
 import DynFlags
 import Unique
 import UniqFM
-import PprCmm ()
 
 import qualified Data.IntSet as IntSet
 import Data.List (partition)
diff --git a/compiler/cmm/Debug.hs b/compiler/cmm/Debug.hs
index da37495530..4aec63fad6 100644
--- a/compiler/cmm/Debug.hs
+++ b/compiler/cmm/Debug.hs
@@ -32,7 +32,6 @@ import CoreSyn
 import FastString      ( nilFS, mkFastString )
 import Module
 import Outputable
-import PprCore         ()
 import PprCmmExpr      ( pprExpr )
 import SrcLoc
 import Util            ( seqList )
diff --git a/compiler/cmm/PprC.hs b/compiler/cmm/PprC.hs
index 7227edd57e..d412969ca7 100644
--- a/compiler/cmm/PprC.hs
+++ b/compiler/cmm/PprC.hs
@@ -32,7 +32,7 @@ import BlockId
 import CLabel
 import ForeignCall
 import Cmm hiding (pprBBlock)
-import PprCmm ()
+import PprCmm () -- For Outputable instances
 import Hoopl.Block
 import Hoopl.Collections
 import Hoopl.Graph
diff --git a/compiler/cmm/PprCmm.hs b/compiler/cmm/PprCmm.hs
index 90f26e4247..397a666022 100644
--- a/compiler/cmm/PprCmm.hs
+++ b/compiler/cmm/PprCmm.hs
@@ -41,7 +41,6 @@ where
 
 import GhcPrelude hiding (succ)
 
-import BlockId ()
 import CLabel
 import Cmm
 import CmmUtils
@@ -52,7 +51,6 @@ import Outputable
 import PprCmmDecl
 import PprCmmExpr
 import Util
-import PprCore ()
 
 import BasicTypes
 import Hoopl.Block
diff --git a/compiler/codeGen/StgCmmClosure.hs b/compiler/codeGen/StgCmmClosure.hs
index 74de2d8756..437219bf45 100644
--- a/compiler/codeGen/StgCmmClosure.hs
+++ b/compiler/codeGen/StgCmmClosure.hs
@@ -71,7 +71,7 @@ import GhcPrelude
 import StgSyn
 import SMRep
 import Cmm
-import PprCmmExpr()
+import PprCmmExpr() -- For Outputable instances
 
 import CostCentre
 import BlockId
diff --git a/compiler/coreSyn/CoreSubst.hs b/compiler/coreSyn/CoreSubst.hs
index 695c7a2f9d..2e3a0087f1 100644
--- a/compiler/coreSyn/CoreSubst.hs
+++ b/compiler/coreSyn/CoreSubst.hs
@@ -61,7 +61,6 @@ import UniqSupply
 import Maybes
 import Util
 import Outputable
-import PprCore          ()              -- Instances
 import Data.List
 
 
diff --git a/compiler/coreSyn/CoreUnfold.hs b/compiler/coreSyn/CoreUnfold.hs
index 4570d7a8aa..8a51e587ad 100644
--- a/compiler/coreSyn/CoreUnfold.hs
+++ b/compiler/coreSyn/CoreUnfold.hs
@@ -46,7 +46,6 @@ import GhcPrelude
 
 import DynFlags
 import CoreSyn
-import PprCore          ()      -- Instances
 import OccurAnal        ( occurAnalyseExpr_NoBinderSwap )
 import CoreOpt
 import CoreArity       ( manifestArity )
diff --git a/compiler/hsSyn/HsBinds.hs b/compiler/hsSyn/HsBinds.hs
index c5fadc0b4a..4be761e3ac 100644
--- a/compiler/hsSyn/HsBinds.hs
+++ b/compiler/hsSyn/HsBinds.hs
@@ -28,7 +28,6 @@ import {-# SOURCE #-} HsPat  ( LPat )
 
 import HsExtension
 import HsTypes
-import PprCore ()
 import CoreSyn
 import TcEvidence
 import Type
diff --git a/compiler/hsSyn/HsSyn.hs b/compiler/hsSyn/HsSyn.hs
index e04abbf70f..622f1b9c77 100644
--- a/compiler/hsSyn/HsSyn.hs
+++ b/compiler/hsSyn/HsSyn.hs
@@ -50,7 +50,7 @@ import HsTypes
 import BasicTypes       ( Fixity, WarningTxt )
 import HsUtils
 import HsDoc
-import HsInstances ()
+import HsInstances () -- For Data instances
 
 -- others:
 import Outputable
diff --git a/compiler/hsSyn/HsTypes.hs b/compiler/hsSyn/HsTypes.hs
index 08b8eade7d..ad9c186c76 100644
--- a/compiler/hsSyn/HsTypes.hs
+++ b/compiler/hsSyn/HsTypes.hs
@@ -77,7 +77,6 @@ import GhcPrelude
 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
 
 import HsExtension
-import HsLit () -- for instances
 
 import Id ( Id )
 import Name( Name )
diff --git a/compiler/iface/FlagChecker.hs b/compiler/iface/FlagChecker.hs
index a9ab4c97d7..34b55e9fef 100644
--- a/compiler/iface/FlagChecker.hs
+++ b/compiler/iface/FlagChecker.hs
@@ -11,7 +11,6 @@ module FlagChecker (
 import GhcPrelude
 
 import Binary
-import BinIface ()
 import DynFlags
 import HscTypes
 import Module
diff --git a/compiler/iface/IfaceSyn.hs b/compiler/iface/IfaceSyn.hs
index 3da0c63174..688998f96d 100644
--- a/compiler/iface/IfaceSyn.hs
+++ b/compiler/iface/IfaceSyn.hs
@@ -46,7 +46,6 @@ import GhcPrelude
 import IfaceType
 import BinFingerprint
 import CoreSyn( IsOrphan, isOrphan )
-import PprCore()            -- Printing DFunArgs
 import DynFlags( gopt, GeneralFlag (Opt_PrintAxiomIncomps) )
 import Demand
 import Class
diff --git a/compiler/main/HeaderInfo.hs b/compiler/main/HeaderInfo.hs
index c7557922bc..0d7e6fd702 100644
--- a/compiler/main/HeaderInfo.hs
+++ b/compiler/main/HeaderInfo.hs
@@ -35,7 +35,6 @@ import DynFlags
 import ErrUtils
 import Util
 import Outputable
-import Pretty           ()
 import Maybes
 import Bag              ( emptyBag, listToBag, unitBag )
 import MonadUtils
diff --git a/compiler/nativeGen/BlockLayout.hs b/compiler/nativeGen/BlockLayout.hs
index 8904b4113b..3755ed5db6 100644
--- a/compiler/nativeGen/BlockLayout.hs
+++ b/compiler/nativeGen/BlockLayout.hs
@@ -37,7 +37,6 @@ import Maybes
 --import Debug
 --import Debug.Trace
 import ListSetOps (removeDups)
-import PprCmm ()
 
 import OrdList
 import Data.List
diff --git a/compiler/nativeGen/CFG.hs b/compiler/nativeGen/CFG.hs
index af0c6da455..44ddecd216 100644
--- a/compiler/nativeGen/CFG.hs
+++ b/compiler/nativeGen/CFG.hs
@@ -56,7 +56,7 @@ import Outputable
 --import Debug
 --import OrdList
 --import Debug.Trace
-import PprCmm ()
+import PprCmm () -- For Outputable instances
 import qualified DynFlags as D
 
 import Data.List
diff --git a/compiler/nativeGen/PPC/Ppr.hs b/compiler/nativeGen/PPC/Ppr.hs
index 4254f23122..0c3aaccda2 100644
--- a/compiler/nativeGen/PPC/Ppr.hs
+++ b/compiler/nativeGen/PPC/Ppr.hs
@@ -27,7 +27,7 @@ import Hoopl.Label
 
 import BlockId
 import CLabel
-import PprCmmExpr ()
+import PprCmmExpr () -- For Outputable instances
 
 import Unique                ( pprUniqueAlways, getUnique )
 import GHC.Platform
diff --git a/compiler/nativeGen/RegAlloc/Graph/Stats.hs b/compiler/nativeGen/RegAlloc/Graph/Stats.hs
index 487e3ee03a..f765224072 100644
--- a/compiler/nativeGen/RegAlloc/Graph/Stats.hs
+++ b/compiler/nativeGen/RegAlloc/Graph/Stats.hs
@@ -28,7 +28,6 @@ import RegClass
 import Reg
 import TargetReg
 
-import PprCmm()
 import Outputable
 import UniqFM
 import UniqSet
diff --git a/compiler/nativeGen/RegAlloc/Liveness.hs b/compiler/nativeGen/RegAlloc/Liveness.hs
index bbb7976a75..3f160ea678 100644
--- a/compiler/nativeGen/RegAlloc/Liveness.hs
+++ b/compiler/nativeGen/RegAlloc/Liveness.hs
@@ -45,7 +45,6 @@ import CFG
 import Hoopl.Collections
 import Hoopl.Label
 import Cmm hiding (RegSet, emptyRegSet)
-import PprCmm()
 
 import Digraph
 import DynFlags
diff --git a/compiler/nativeGen/SPARC/CodeGen.hs b/compiler/nativeGen/SPARC/CodeGen.hs
index 056d0c6fbf..bb8bbe16b6 100644
--- a/compiler/nativeGen/SPARC/CodeGen.hs
+++ b/compiler/nativeGen/SPARC/CodeGen.hs
@@ -31,7 +31,6 @@ import SPARC.CodeGen.CondCode
 import SPARC.CodeGen.Gen64
 import SPARC.CodeGen.Gen32
 import SPARC.CodeGen.Base
-import SPARC.Ppr        ()
 import SPARC.Instr
 import SPARC.Imm
 import SPARC.AddrMode
diff --git a/compiler/nativeGen/SPARC/CodeGen/Base.hs b/compiler/nativeGen/SPARC/CodeGen/Base.hs
index e64af0c44e..97c54a9364 100644
--- a/compiler/nativeGen/SPARC/CodeGen/Base.hs
+++ b/compiler/nativeGen/SPARC/CodeGen/Base.hs
@@ -25,7 +25,7 @@ import Reg
 import CodeGen.Platform
 import DynFlags
 import Cmm
-import PprCmmExpr ()
+import PprCmmExpr () -- For Outputable instances
 import GHC.Platform
 
 import Outputable
diff --git a/compiler/nativeGen/SPARC/CodeGen/Expand.hs b/compiler/nativeGen/SPARC/CodeGen/Expand.hs
index 0b318740db..a29c24dcd4 100644
--- a/compiler/nativeGen/SPARC/CodeGen/Expand.hs
+++ b/compiler/nativeGen/SPARC/CodeGen/Expand.hs
@@ -11,7 +11,6 @@ import SPARC.Instr
 import SPARC.Imm
 import SPARC.AddrMode
 import SPARC.Regs
-import SPARC.Ppr        ()
 import Instruction
 import Reg
 import Format
diff --git a/compiler/nativeGen/SPARC/CodeGen/Gen64.hs b/compiler/nativeGen/SPARC/CodeGen/Gen64.hs
index 6fa7482f9b..18df9e19a3 100644
--- a/compiler/nativeGen/SPARC/CodeGen/Gen64.hs
+++ b/compiler/nativeGen/SPARC/CodeGen/Gen64.hs
@@ -16,7 +16,7 @@ import SPARC.Regs
 import SPARC.AddrMode
 import SPARC.Imm
 import SPARC.Instr
-import SPARC.Ppr()
+-- import SPARC.Ppr()
 import NCGMonad
 import Instruction
 import Format
diff --git a/compiler/nativeGen/SPARC/CodeGen/Sanity.hs b/compiler/nativeGen/SPARC/CodeGen/Sanity.hs
index fcf5b65bde..7f9bfed229 100644
--- a/compiler/nativeGen/SPARC/CodeGen/Sanity.hs
+++ b/compiler/nativeGen/SPARC/CodeGen/Sanity.hs
@@ -9,7 +9,7 @@ where
 import GhcPrelude
 
 import SPARC.Instr
-import SPARC.Ppr        ()
+import SPARC.Ppr        () -- For Outputable instances
 import Instruction
 
 import Cmm
diff --git a/compiler/nativeGen/SPARC/Ppr.hs b/compiler/nativeGen/SPARC/Ppr.hs
index fc67f77541..2bec7ec01f 100644
--- a/compiler/nativeGen/SPARC/Ppr.hs
+++ b/compiler/nativeGen/SPARC/Ppr.hs
@@ -39,7 +39,7 @@ import Format
 import PprBase
 
 import Cmm hiding (topInfoTable)
-import PprCmm()
+import PprCmm() -- For Outputable instances
 import BlockId
 import CLabel
 import Hoopl.Label
diff --git a/compiler/nativeGen/X86/CodeGen.hs b/compiler/nativeGen/X86/CodeGen.hs
index 13662f6807..4aeb4eb635 100644
--- a/compiler/nativeGen/X86/CodeGen.hs
+++ b/compiler/nativeGen/X86/CodeGen.hs
@@ -38,9 +38,6 @@ import X86.Cond
 import X86.Regs
 import X86.RegInfo
 
---TODO: Remove - Just for development/debugging
-import X86.Ppr()
-
 import CodeGen.Platform
 import CPrim
 import Debug            ( DebugBlock(..), UnwindPoint(..), UnwindTable
@@ -60,7 +57,6 @@ import GHC.Platform
 import BasicTypes
 import BlockId
 import Module           ( primUnitId )
-import PprCmm           ()
 import CmmUtils
 import CmmSwitch
 import Cmm
diff --git a/compiler/typecheck/TcSimplify.hs b/compiler/typecheck/TcSimplify.hs
index d16be28773..5a7924017d 100644
--- a/compiler/typecheck/TcSimplify.hs
+++ b/compiler/typecheck/TcSimplify.hs
@@ -48,7 +48,6 @@ import TcMType   as TcM
 import TcRnMonad as TcM
 import TcSMonad  as TcS
 import TcType
-import TrieMap       () -- DV: for now
 import Type
 import TysWiredIn    ( liftedRepTy )
 import Unify         ( tcMatchTyKi )
diff --git a/libraries/base/GHC/Err.hs b/libraries/base/GHC/Err.hs
index 26e3f2059d..17b5b8ec41 100644
--- a/libraries/base/GHC/Err.hs
+++ b/libraries/base/GHC/Err.hs
@@ -23,7 +23,6 @@
 -----------------------------------------------------------------------------
 
 module GHC.Err( absentErr, error, errorWithoutStackTrace, undefined ) where
-import GHC.CString ()
 import GHC.Types (Char, RuntimeRep)
 import GHC.Stack.Types
 import GHC.Prim
diff --git a/libraries/ghc-prim/GHC/Magic.hs b/libraries/ghc-prim/GHC/Magic.hs
index 2cc3212d95..403c3f0cca 100644
--- a/libraries/ghc-prim/GHC/Magic.hs
+++ b/libraries/ghc-prim/GHC/Magic.hs
@@ -39,7 +39,6 @@ module GHC.Magic ( inline, noinline, lazy, oneShot, runRW# ) where
 import GHC.Prim (realWorld#)
 #endif
 import GHC.Prim (State#, RealWorld)
-import GHC.CString ()
 import GHC.Types (RuntimeRep, TYPE)
 
 -- | The call @inline f@ arranges that @f@ is inlined, regardless of
diff --git a/libraries/ghci/GHCi/Message.hs b/libraries/ghci/GHCi/Message.hs
index d8c27b0702..70c532fc94 100644
--- a/libraries/ghci/GHCi/Message.hs
+++ b/libraries/ghci/GHCi/Message.hs
@@ -25,7 +25,7 @@ module GHCi.Message
 import Prelude -- See note [Why do we import Prelude here?]
 import GHCi.RemoteTypes
 import GHCi.FFI
-import GHCi.TH.Binary ()
+import GHCi.TH.Binary () -- For Binary instances
 import GHCi.BreakArray
 
 import GHC.LanguageExtensions