Refactor ModuleName to L.H.S.Module.Name

ModuleName used to live in GHC.Unit.Module.Name. In this commit, the
definition of ModuleName and its associated functions are moved to
Language.Haskell.Syntax.Module.Name according to the current plan
towards making the AST GHC-independent.

The instances for ModuleName for Outputable, Uniquable and Binary were
moved to the module in which the class is defined because these instances
depend on GHC.

The instance of Eq for ModuleName is slightly changed to no longer
depend on unique explicitly and instead uses FastString's instance of
Eq.

31 files changed, 80 insertions, 89 deletions

diff --git a/compiler/GHC.hs b/compiler/GHC.hs
index 29a287efb4..95d35b85bd 100644
--- a/compiler/GHC.hs
+++ b/compiler/GHC.hs
@@ -175,7 +175,6 @@ module GHC (
 
         -- ** Modules
         Module, mkModule, pprModule, moduleName, moduleUnit,
-        mkModuleName, moduleNameString,
 
         -- ** Names
         Name,
diff --git a/compiler/GHC/Builtin/Names.hs b/compiler/GHC/Builtin/Names.hs
index dba466aa8d..115a7f53f4 100644
--- a/compiler/GHC/Builtin/Names.hs
+++ b/compiler/GHC/Builtin/Names.hs
@@ -136,7 +136,6 @@ where
 import GHC.Prelude
 
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import GHC.Types.Name.Occurrence
 import GHC.Types.Name.Reader
 import GHC.Types.Unique
@@ -145,6 +144,8 @@ import GHC.Types.Name
 import GHC.Types.SrcLoc
 import GHC.Data.FastString
 
+import Language.Haskell.Syntax.Module.Name
+
 {-
 ************************************************************************
 *                                                                      *
diff --git a/compiler/GHC/Builtin/Names/TH.hs b/compiler/GHC/Builtin/Names/TH.hs
index 2eb5e13530..3908f5091c 100644
--- a/compiler/GHC/Builtin/Names/TH.hs
+++ b/compiler/GHC/Builtin/Names/TH.hs
@@ -10,7 +10,6 @@ import GHC.Prelude ()
 
 import GHC.Builtin.Names( mk_known_key_name )
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import GHC.Types.Name( Name )
 import GHC.Types.Name.Occurrence( tcName, clsName, dataName, varName )
 import GHC.Types.Name.Reader( RdrName, nameRdrName )
@@ -18,6 +17,8 @@ import GHC.Types.Unique
 import GHC.Builtin.Uniques
 import GHC.Data.FastString
 
+import Language.Haskell.Syntax.Module.Name
+
 -- To add a name, do three things
 --
 --  1) Allocate a key
diff --git a/compiler/GHC/ByteCode/Linker.hs b/compiler/GHC/ByteCode/Linker.hs
index c9339317d2..c3af3d4e85 100644
--- a/compiler/GHC/ByteCode/Linker.hs
+++ b/compiler/GHC/ByteCode/Linker.hs
@@ -31,7 +31,6 @@ import GHC.Builtin.PrimOps
 import GHC.Builtin.Names
 
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 
 import GHC.Data.FastString
 import GHC.Data.SizedSeq
@@ -43,6 +42,8 @@ import GHC.Utils.Outputable
 import GHC.Types.Name
 import GHC.Types.Name.Env
 
+import Language.Haskell.Syntax.Module.Name
+
 -- Standard libraries
 import Data.Array.Unboxed
 import Foreign.Ptr
diff --git a/compiler/GHC/Core/DataCon.hs b/compiler/GHC/Core/DataCon.hs
index 01ab6414c3..0d436a93f0 100644
--- a/compiler/GHC/Core/DataCon.hs
+++ b/compiler/GHC/Core/DataCon.hs
@@ -86,7 +86,6 @@ import GHC.Types.Var.Env
 import GHC.Types.Basic
 import GHC.Data.FastString
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import GHC.Utils.Binary
 import GHC.Types.Unique.FM ( UniqFM )
 import GHC.Types.Unique.Set
@@ -105,6 +104,8 @@ import qualified Data.Data as Data
 import Data.Char
 import Data.List( find )
 
+import Language.Haskell.Syntax.Module.Name
+
 {-
 Data constructor representation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/compiler/GHC/Core/Opt/CallerCC.hs b/compiler/GHC/Core/Opt/CallerCC.hs
index ba9f809092..1bdb4d7afc 100644
--- a/compiler/GHC/Core/Opt/CallerCC.hs
+++ b/compiler/GHC/Core/Opt/CallerCC.hs
@@ -31,7 +31,6 @@ import GHC.Types.CostCentre
 import GHC.Types.CostCentre.State
 import GHC.Types.Name hiding (varName)
 import GHC.Types.Tickish
-import GHC.Unit.Module.Name
 import GHC.Unit.Module.ModGuts
 import GHC.Types.SrcLoc
 import GHC.Types.Var
@@ -43,6 +42,8 @@ import GHC.Utils.Panic
 import qualified GHC.Utils.Binary as B
 import Data.Char
 
+import Language.Haskell.Syntax.Module.Name
+
 addCallerCostCentres :: ModGuts -> CoreM ModGuts
 addCallerCostCentres guts = do
   dflags <- getDynFlags
diff --git a/compiler/GHC/Core/Opt/Simplify.hs b/compiler/GHC/Core/Opt/Simplify.hs
index de049523cc..d26fd28de2 100644
--- a/compiler/GHC/Core/Opt/Simplify.hs
+++ b/compiler/GHC/Core/Opt/Simplify.hs
@@ -66,7 +66,7 @@ import GHC.Builtin.Names( runRWKey )
 
 import GHC.Data.Maybe   ( isNothing, orElse )
 import GHC.Data.FastString
-import GHC.Unit.Module ( moduleName, pprModuleName )
+import GHC.Unit.Module ( moduleName )
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
diff --git a/compiler/GHC/Driver/Pipeline.hs-boot b/compiler/GHC/Driver/Pipeline.hs-boot
index 3467ff4ced..72ba57a0d1 100644
--- a/compiler/GHC/Driver/Pipeline.hs-boot
+++ b/compiler/GHC/Driver/Pipeline.hs-boot
@@ -5,9 +5,10 @@ import GHC.Driver.Env.Types ( HscEnv )
 import GHC.ForeignSrcLang ( ForeignSrcLang )
 import GHC.Prelude (FilePath, IO)
 import GHC.Unit.Module.Location (ModLocation)
-import GHC.Unit.Module.Name (ModuleName)
 import GHC.Driver.Session (DynFlags)
 
+import Language.Haskell.Syntax.Module.Name
+
 -- These are used in GHC.Driver.Pipeline.Execute, but defined in terms of runPipeline
 compileForeign :: HscEnv -> ForeignSrcLang -> FilePath -> IO FilePath
 compileEmptyStub :: DynFlags -> HscEnv -> FilePath -> ModLocation -> ModuleName -> IO ()
diff --git a/compiler/GHC/Driver/Pipeline/Execute.hs b/compiler/GHC/Driver/Pipeline/Execute.hs
index ff62a9a6db..7390735f28 100644
--- a/compiler/GHC/Driver/Pipeline/Execute.hs
+++ b/compiler/GHC/Driver/Pipeline/Execute.hs
@@ -22,7 +22,6 @@ import GHC.Driver.Pipeline.Phases
 import GHC.Driver.Env hiding (Hsc)
 import GHC.Unit.Module.Location
 import GHC.Driver.Phases
-import GHC.Unit.Module.Name ( ModuleName )
 import GHC.Unit.Types
 import GHC.Types.SourceFile
 import GHC.Unit.Module.Status
@@ -83,6 +82,8 @@ import GHC.Driver.Env.KnotVars
 import GHC.Driver.Config.Finder
 import GHC.Rename.Names
 
+import Language.Haskell.Syntax.Module.Name
+
 newtype HookedUse a = HookedUse { runHookedUse :: (Hooks, PhaseHook) -> IO a }
   deriving (Functor, Applicative, Monad, MonadIO, MonadThrow, MonadCatch) via (ReaderT (Hooks, PhaseHook) IO)
 
diff --git a/compiler/GHC/Driver/Pipeline/Phases.hs b/compiler/GHC/Driver/Pipeline/Phases.hs
index 431c9e0b1d..aa11801b45 100644
--- a/compiler/GHC/Driver/Pipeline/Phases.hs
+++ b/compiler/GHC/Driver/Pipeline/Phases.hs
@@ -16,11 +16,12 @@ import GHC.Types.Error
 import GHC.Driver.Errors.Types
 import GHC.Fingerprint.Type
 import GHC.Unit.Module.Location ( ModLocation )
-import GHC.Unit.Module.Name ( ModuleName )
 import GHC.Unit.Module.ModIface
 import GHC.Linker.Types
 import GHC.Driver.Phases
 
+import Language.Haskell.Syntax.Module.Name ( ModuleName )
+
 -- Typed Pipeline Phases
 -- MP: TODO: We need to refine the arguments to each of these phases so recompilation
 -- can be smarter. For example, rather than passing a whole HscEnv, just pass the options
diff --git a/compiler/GHC/Hs/Doc.hs b/compiler/GHC/Hs/Doc.hs
index 91f584c8d9..209f9608eb 100644
--- a/compiler/GHC/Hs/Doc.hs
+++ b/compiler/GHC/Hs/Doc.hs
@@ -36,7 +36,6 @@ import qualified GHC.Data.EnumSet as EnumSet
 import GHC.Data.EnumSet (EnumSet)
 import GHC.Types.Avail
 import GHC.Types.Name.Set
-import GHC.Unit.Module.Name
 import GHC.Driver.Flags
 
 import Control.Applicative (liftA2)
@@ -48,13 +47,15 @@ import qualified Data.Map as Map
 import Data.List.NonEmpty (NonEmpty(..))
 import GHC.LanguageExtensions.Type
 import qualified GHC.Utils.Outputable as O
-import Language.Haskell.Syntax.Extension
 import GHC.Hs.Extension
 import GHC.Types.Unique.Map
 import Data.List (sortBy)
 
 import GHC.Hs.DocString
 
+import Language.Haskell.Syntax.Extension
+import Language.Haskell.Syntax.Module.Name
+
 -- | A docstring with the (probable) identifiers found in it.
 type HsDoc = WithHsDocIdentifiers HsDocString
 
diff --git a/compiler/GHC/Hs/ImpExp.hs b/compiler/GHC/Hs/ImpExp.hs
index 1f13d8a2fe..06500705ba 100644
--- a/compiler/GHC/Hs/ImpExp.hs
+++ b/compiler/GHC/Hs/ImpExp.hs
@@ -29,8 +29,6 @@ import GHC.Types.FieldLabel   ( FieldLabel )
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Types.SrcLoc
-import Language.Haskell.Syntax.Extension
-import Language.Haskell.Syntax.ImpExp
 import GHC.Parser.Annotation
 import GHC.Hs.Extension
 import GHC.Types.Name
@@ -39,6 +37,10 @@ import GHC.Types.PkgQual
 import Data.Data
 import Data.Maybe
 
+import Language.Haskell.Syntax.Extension
+import Language.Haskell.Syntax.Module.Name
+import Language.Haskell.Syntax.ImpExp
+
 {-
 ************************************************************************
 *                                                                      *
diff --git a/compiler/GHC/Tc/Deriv/Generics.hs b/compiler/GHC/Tc/Deriv/Generics.hs
index 6240de3205..bae4ca79bf 100644
--- a/compiler/GHC/Tc/Deriv/Generics.hs
+++ b/compiler/GHC/Tc/Deriv/Generics.hs
@@ -33,8 +33,8 @@ import GHC.Core.DataCon
 import GHC.Core.TyCon
 import GHC.Core.FamInstEnv ( FamInst, FamFlavor(..), mkSingleCoAxiom )
 import GHC.Tc.Instance.Family
-import GHC.Unit.Module ( moduleName, moduleNameFS
-                        , moduleUnit, unitFS, getModule )
+import GHC.Unit.Module ( moduleName, moduleUnit
+                       , unitFS, getModule )
 import GHC.Iface.Env    ( newGlobalBinder )
 import GHC.Types.Name hiding ( varName )
 import GHC.Types.Name.Reader
diff --git a/compiler/GHC/Types/Unique.hs b/compiler/GHC/Types/Unique.hs
index f4538bf579..60d1c452e2 100644
--- a/compiler/GHC/Types/Unique.hs
+++ b/compiler/GHC/Types/Unique.hs
@@ -59,6 +59,8 @@ import GHC.Exts (indexCharOffAddr#, Char(..), Int(..))
 
 import Data.Char        ( chr, ord )
 
+import Language.Haskell.Syntax.Module.Name
+
 {-
 ************************************************************************
 *                                                                      *
@@ -187,6 +189,10 @@ instance Uniquable FastString where
 instance Uniquable Int where
  getUnique i = mkUniqueGrimily i
 
+instance Uniquable ModuleName where
+  getUnique (ModuleName nm) = getUnique nm
+
+
 {-
 ************************************************************************
 *                                                                      *
diff --git a/compiler/GHC/Unit/Home.hs b/compiler/GHC/Unit/Home.hs
index c72d21e537..4f871d10fb 100644
--- a/compiler/GHC/Unit/Home.hs
+++ b/compiler/GHC/Unit/Home.hs
@@ -33,9 +33,10 @@ where
 
 import GHC.Prelude
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import Data.Maybe
 
+import Language.Haskell.Syntax.Module.Name
+
 -- | Information about the home unit (i.e., the until that will contain the
 -- modules we are compiling)
 --
diff --git a/compiler/GHC/Unit/Module.hs b/compiler/GHC/Unit/Module.hs
index b9813b95f5..7ae0059b71 100644
--- a/compiler/GHC/Unit/Module.hs
+++ b/compiler/GHC/Unit/Module.hs
@@ -18,7 +18,7 @@ module GHC.Unit.Module
     ( module GHC.Unit.Types
 
       -- * The ModuleName type
-    , module GHC.Unit.Module.Name
+    , module Language.Haskell.Syntax.Module.Name
 
       -- * The ModLocation type
     , module GHC.Unit.Module.Location
@@ -47,11 +47,12 @@ import GHC.Prelude
 
 import GHC.Types.Unique.DSet
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import GHC.Unit.Module.Location
 import GHC.Unit.Module.Env
 import GHC.Utils.Misc
 
+import Language.Haskell.Syntax.Module.Name
+
 -- | A 'Module' is definite if it has no free holes.
 moduleIsDefinite :: Module -> Bool
 moduleIsDefinite = isEmptyUniqDSet . moduleFreeHoles
diff --git a/compiler/GHC/Unit/Module/Deps.hs b/compiler/GHC/Unit/Module/Deps.hs
index 5a50f42b35..9099ee2f0d 100644
--- a/compiler/GHC/Unit/Module/Deps.hs
+++ b/compiler/GHC/Unit/Module/Deps.hs
@@ -24,7 +24,6 @@ import GHC.Prelude
 import GHC.Types.SafeHaskell
 import GHC.Types.Name
 
-import GHC.Unit.Module.Name
 import GHC.Unit.Module.Imported
 import GHC.Unit.Module
 import GHC.Unit.Home
diff --git a/compiler/GHC/Unit/Module/Env.hs b/compiler/GHC/Unit/Module/Env.hs
index e8307229f7..32ca0b12cd 100644
--- a/compiler/GHC/Unit/Module/Env.hs
+++ b/compiler/GHC/Unit/Module/Env.hs
@@ -37,7 +37,6 @@ where
 
 import GHC.Prelude
 
-import GHC.Unit.Module.Name (ModuleName)
 import GHC.Types.Unique
 import GHC.Types.Unique.FM
 import GHC.Types.Unique.DFM
@@ -54,6 +53,8 @@ import qualified Data.Set as Set
 import qualified GHC.Data.FiniteMap as Map
 import GHC.Utils.Outputable
 
+import Language.Haskell.Syntax.Module.Name
+
 -- | A map keyed off of 'Module's
 newtype ModuleEnv elt = ModuleEnv (Map NDModule elt)
 
diff --git a/compiler/GHC/Unit/Parser.hs b/compiler/GHC/Unit/Parser.hs
index f9735306de..bac6ba4bf1 100644
--- a/compiler/GHC/Unit/Parser.hs
+++ b/compiler/GHC/Unit/Parser.hs
@@ -10,13 +10,14 @@ where
 import GHC.Prelude
 
 import GHC.Unit.Types
-import GHC.Unit.Module.Name
 import GHC.Data.FastString
 
 import qualified Text.ParserCombinators.ReadP as Parse
 import Text.ParserCombinators.ReadP (ReadP, (<++))
 import Data.Char (isAlphaNum)
 
+import Language.Haskell.Syntax.Module.Name (ModuleName, parseModuleName)
+
 parseUnit :: ReadP Unit
 parseUnit = parseVirtUnitId <++ parseDefUnitId
   where
@@ -55,4 +56,3 @@ parseModSubst = Parse.between (Parse.char '[') (Parse.char ']')
            v <- parseHoleyModule
            return (k, v)
 
-
diff --git a/compiler/GHC/Unit/Types.hs b/compiler/GHC/Unit/Types.hs
index e99fea94d4..f71ce9c02e 100644
--- a/compiler/GHC/Unit/Types.hs
+++ b/compiler/GHC/Unit/Types.hs
@@ -91,7 +91,6 @@ where
 import GHC.Prelude
 import GHC.Types.Unique
 import GHC.Types.Unique.DSet
-import GHC.Unit.Module.Name
 import GHC.Utils.Binary
 import GHC.Utils.Outputable
 import GHC.Data.FastString
@@ -107,6 +106,7 @@ import Data.Bifunctor
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Char8 as BS.Char8
 
+import Language.Haskell.Syntax.Module.Name
 import {-# SOURCE #-} Language.Haskell.Syntax.ImpExp (IsBootInterface(..))
 
 ---------------------------------------------------------------------
diff --git a/compiler/GHC/Unit/Types.hs-boot b/compiler/GHC/Unit/Types.hs-boot
index 21a0f6bc79..a7e09126d5 100644
--- a/compiler/GHC/Unit/Types.hs-boot
+++ b/compiler/GHC/Unit/Types.hs-boot
@@ -3,7 +3,7 @@ module GHC.Unit.Types where
 
 import GHC.Prelude ()
 import {-# SOURCE #-} GHC.Utils.Outputable
-import {-# SOURCE #-} Language.Haskell.Syntax.ImpExp ( ModuleName )
+import Language.Haskell.Syntax.Module.Name (ModuleName)
 import Data.Kind (Type)
 
 data UnitId
diff --git a/compiler/GHC/Utils/Binary.hs b/compiler/GHC/Utils/Binary.hs
index 15071c1b37..5e11489572 100644
--- a/compiler/GHC/Utils/Binary.hs
+++ b/compiler/GHC/Utils/Binary.hs
@@ -77,6 +77,8 @@ module GHC.Utils.Binary
 
 import GHC.Prelude
 
+import Language.Haskell.Syntax.Module.Name (ModuleName(..))
+
 import {-# SOURCE #-} GHC.Types.Name (Name)
 import GHC.Data.FastString
 import GHC.Utils.Panic.Plain
@@ -1103,6 +1105,10 @@ instance Binary Fingerprint where
   put_ h (Fingerprint w1 w2) = do put_ h w1; put_ h w2
   get  h = do w1 <- get h; w2 <- get h; return (Fingerprint w1 w2)
 
+instance Binary ModuleName where
+  put_ bh (ModuleName fs) = put_ bh fs
+  get bh = do fs <- get bh; return (ModuleName fs)
+
 -- instance Binary FunctionOrData where
 --     put_ bh IsFunction = putByte bh 0
 --     put_ bh IsData     = putByte bh 1
diff --git a/compiler/GHC/Utils/Outputable.hs b/compiler/GHC/Utils/Outputable.hs
index 09575cf53d..6ff57e5775 100644
--- a/compiler/GHC/Utils/Outputable.hs
+++ b/compiler/GHC/Utils/Outputable.hs
@@ -78,6 +78,8 @@ module GHC.Utils.Outputable (
 
         pprFastFilePath, pprFilePathString,
 
+        pprModuleName,
+
         -- * Controlling the style in which output is printed
         BindingSite(..),
 
@@ -104,7 +106,7 @@ module GHC.Utils.Outputable (
 
     ) where
 
-import {-# SOURCE #-} Language.Haskell.Syntax.ImpExp ( ModuleName )
+import Language.Haskell.Syntax.Module.Name ( ModuleName(..) )
 
 import GHC.Prelude
 
@@ -1039,6 +1041,16 @@ instance Outputable Serialized where
 instance Outputable Extension where
     ppr = text . show
 
+instance Outputable ModuleName where
+  ppr = pprModuleName
+
+pprModuleName :: ModuleName -> SDoc
+pprModuleName (ModuleName nm) =
+    getPprStyle $ \ sty ->
+    if codeStyle sty
+        then ztext (zEncodeFS nm)
+        else ftext nm
+
 -----------------------------------------------------------------------
 -- The @OutputableP@ class
 -----------------------------------------------------------------------
diff --git a/compiler/Language/Haskell/Syntax.hs b/compiler/Language/Haskell/Syntax.hs
index d5129cbb13..82e9f5558d 100644
--- a/compiler/Language/Haskell/Syntax.hs
+++ b/compiler/Language/Haskell/Syntax.hs
@@ -22,6 +22,7 @@ module Language.Haskell.Syntax (
         module Language.Haskell.Syntax.Expr,
         module Language.Haskell.Syntax.ImpExp,
         module Language.Haskell.Syntax.Lit,
+        module Language.Haskell.Syntax.Module.Name,
         module Language.Haskell.Syntax.Pat,
         module Language.Haskell.Syntax.Type,
         module Language.Haskell.Syntax.Extension,
@@ -32,6 +33,7 @@ import Language.Haskell.Syntax.Decls
 import Language.Haskell.Syntax.Binds
 import Language.Haskell.Syntax.Expr
 import Language.Haskell.Syntax.ImpExp
+import Language.Haskell.Syntax.Module.Name
 import Language.Haskell.Syntax.Lit
 import Language.Haskell.Syntax.Extension
 import Language.Haskell.Syntax.Pat
diff --git a/compiler/Language/Haskell/Syntax/ImpExp.hs b/compiler/Language/Haskell/Syntax/ImpExp.hs
index 7e529701c4..b31c417936 100644
--- a/compiler/Language/Haskell/Syntax/ImpExp.hs
+++ b/compiler/Language/Haskell/Syntax/ImpExp.hs
@@ -3,6 +3,7 @@
 module Language.Haskell.Syntax.ImpExp where
 
 import Language.Haskell.Syntax.Extension
+import Language.Haskell.Syntax.Module.Name
 
 import Data.Eq (Eq)
 import Data.Ord (Ord)
@@ -14,7 +15,6 @@ import Data.String (String)
 import Data.Int (Int)
 
 import GHC.Hs.Doc -- ROMES:TODO Discuss in #21592 whether this is parsed AST or base AST
-import GHC.Data.FastString
 
 {-
 ************************************************************************
@@ -26,9 +26,6 @@ Import and export declaration lists
 One per import declaration in a module.
 -}
 
--- | A ModuleName is essentially a simple string, e.g. @Data.List@.
-newtype ModuleName = ModuleName FastString deriving Show
-
 -- | Located Import Declaration
 type LImportDecl pass = XRec pass (ImportDecl pass)
         -- ^ When in a list this may have
diff --git a/compiler/Language/Haskell/Syntax/ImpExp.hs-boot b/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
index 9cc78600b8..68bd7fdc53 100644
--- a/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
+++ b/compiler/Language/Haskell/Syntax/ImpExp.hs-boot
@@ -1,7 +1,5 @@
 module Language.Haskell.Syntax.ImpExp where
 
-import GHC.Data.FastString
-
 import Data.Eq
 import Data.Ord
 import Text.Show
@@ -16,7 +14,3 @@ instance Eq IsBootInterface
 instance Ord IsBootInterface
 instance Show IsBootInterface
 instance Data IsBootInterface
-
-newtype ModuleName = ModuleName FastString
-
-instance Show ModuleName
diff --git a/compiler/GHC/Unit/Module/Name.hs b/compiler/Language/Haskell/Syntax/Module/Name.hs
index b7bf62857c..65e64d8700 100644
--- a/compiler/GHC/Unit/Module/Name.hs
+++ b/compiler/Language/Haskell/Syntax/Module/Name.hs
@@ -1,53 +1,22 @@
-{-# OPTIONS_GHC -Wno-orphans #-} -- Outputable and Module Name
-
--- | The ModuleName type
-module GHC.Unit.Module.Name
-    ( ModuleName
-    , pprModuleName
-    , moduleNameFS
-    , moduleNameString
-    , moduleNameSlashes, moduleNameColons
-    , mkModuleName
-    , mkModuleNameFS
-    , stableModuleNameCmp
-    , parseModuleName
-    )
-where
-
-import {-# SOURCE #-} Language.Haskell.Syntax.ImpExp (ModuleName(..))
-
-import GHC.Prelude
-
-import GHC.Utils.Outputable
-import GHC.Types.Unique
-import GHC.Data.FastString
-import GHC.Utils.Binary
-import GHC.Utils.Misc
+module Language.Haskell.Syntax.Module.Name where
 
-import Control.DeepSeq
-import Data.Data
-import System.FilePath
+import Prelude
 
-import qualified Text.ParserCombinators.ReadP as Parse
-import Text.ParserCombinators.ReadP (ReadP)
+import Data.Data
 import Data.Char (isAlphaNum)
+import Control.DeepSeq
+import qualified Text.ParserCombinators.ReadP as Parse
+import System.FilePath
 
-instance Uniquable ModuleName where
-  getUnique (ModuleName nm) = getUnique nm
+import GHC.Utils.Misc (abstractConstr)
+import GHC.Data.FastString
 
-instance Eq ModuleName where
-  nm1 == nm2 = getUnique nm1 == getUnique nm2
+-- | A ModuleName is essentially a simple string, e.g. @Data.List@.
+newtype ModuleName = ModuleName FastString deriving (Show, Eq)
 
 instance Ord ModuleName where
   nm1 `compare` nm2 = stableModuleNameCmp nm1 nm2
 
-instance Outputable ModuleName where
-  ppr = pprModuleName
-
-instance Binary ModuleName where
-  put_ bh (ModuleName fs) = put_ bh fs
-  get bh = do fs <- get bh; return (ModuleName fs)
-
 instance Data ModuleName where
   -- don't traverse?
   toConstr _   = abstractConstr "ModuleName"
@@ -61,13 +30,6 @@ stableModuleNameCmp :: ModuleName -> ModuleName -> Ordering
 -- ^ Compares module names lexically, rather than by their 'Unique's
 stableModuleNameCmp n1 n2 = moduleNameFS n1 `lexicalCompareFS` moduleNameFS n2
 
-pprModuleName :: ModuleName -> SDoc
-pprModuleName (ModuleName nm) =
-    getPprStyle $ \ sty ->
-    if codeStyle sty
-        then ztext (zEncodeFS nm)
-        else ftext nm
-
 moduleNameFS :: ModuleName -> FastString
 moduleNameFS (ModuleName mod) = mod
 
@@ -92,7 +54,7 @@ moduleNameColons :: ModuleName -> String
 moduleNameColons = dots_to_colons . moduleNameString
   where dots_to_colons = map (\c -> if c == '.' then ':' else c)
 
-parseModuleName :: ReadP ModuleName
+parseModuleName :: Parse.ReadP ModuleName
 parseModuleName = fmap mkModuleName
                 $ Parse.munch1 (\c -> isAlphaNum c || c `elem` "_.")
 
diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index e06a2c5837..92b70c9ff8 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -765,7 +765,6 @@ Library
         GHC.Unit.Module.ModGuts
         GHC.Unit.Module.ModIface
         GHC.Unit.Module.ModSummary
-        GHC.Unit.Module.Name
         GHC.Unit.Module.Status
         GHC.Unit.Module.Warnings
         GHC.Unit.Parser
@@ -806,6 +805,7 @@ Library
         Language.Haskell.Syntax.Extension
         Language.Haskell.Syntax.ImpExp
         Language.Haskell.Syntax.Lit
+        Language.Haskell.Syntax.Module.Name
         Language.Haskell.Syntax.Pat
         Language.Haskell.Syntax.Type
 
diff --git a/testsuite/tests/count-deps/CountDepsAst.stdout b/testsuite/tests/count-deps/CountDepsAst.stdout
index edf9f38183..e801360c11 100644
--- a/testsuite/tests/count-deps/CountDepsAst.stdout
+++ b/testsuite/tests/count-deps/CountDepsAst.stdout
@@ -249,7 +249,6 @@ GHC.Unit.Module.ModDetails
 GHC.Unit.Module.ModGuts
 GHC.Unit.Module.ModIface
 GHC.Unit.Module.ModSummary
-GHC.Unit.Module.Name
 GHC.Unit.Module.Status
 GHC.Unit.Module.Warnings
 GHC.Unit.Parser
@@ -287,5 +286,6 @@ Language.Haskell.Syntax.Expr
 Language.Haskell.Syntax.Extension
 Language.Haskell.Syntax.ImpExp
 Language.Haskell.Syntax.Lit
+Language.Haskell.Syntax.Module.Name
 Language.Haskell.Syntax.Pat
 Language.Haskell.Syntax.Type
diff --git a/testsuite/tests/count-deps/CountDepsParser.stdout b/testsuite/tests/count-deps/CountDepsParser.stdout
index 213126ce47..86ab7d3e18 100644
--- a/testsuite/tests/count-deps/CountDepsParser.stdout
+++ b/testsuite/tests/count-deps/CountDepsParser.stdout
@@ -256,7 +256,6 @@ GHC.Unit.Module.ModDetails
 GHC.Unit.Module.ModGuts
 GHC.Unit.Module.ModIface
 GHC.Unit.Module.ModSummary
-GHC.Unit.Module.Name
 GHC.Unit.Module.Status
 GHC.Unit.Module.Warnings
 GHC.Unit.Parser
@@ -294,5 +293,6 @@ Language.Haskell.Syntax.Expr
 Language.Haskell.Syntax.Extension
 Language.Haskell.Syntax.ImpExp
 Language.Haskell.Syntax.Lit
+Language.Haskell.Syntax.Module.Name
 Language.Haskell.Syntax.Pat
 Language.Haskell.Syntax.Type
diff --git a/testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs b/testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs
index a6f160a5e3..5e32e5b1db 100644
--- a/testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs
+++ b/testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs
@@ -3,7 +3,7 @@
 module Main where
 
 import GHC.Core.Opt.CallerCC
-import GHC.Unit.Module.Name
+import Language.Haskell.Syntax.Module.Name
 
 deriving instance Eq CallerCcFilter
 deriving instance Show CallerCcFilter