compiler: introduce custom "GhcPrelude" Prelude

This switches the compiler/ component to get compiled with
-XNoImplicitPrelude and a `import GhcPrelude` is inserted in all
modules.

This is motivated by the upcoming "Prelude" re-export of
`Semigroup((<>))` which would cause lots of name clashes in every
modulewhich imports also `Outputable`

Reviewers: austin, goldfire, bgamari, alanz, simonmar

Reviewed By: bgamari

Subscribers: goldfire, rwbarton, thomie, mpickering, bgamari

Differential Revision: https://phabricator.haskell.org/D3989

45 files changed, 97 insertions, 1 deletions

diff --git a/compiler/utils/AsmUtils.hs b/compiler/utils/AsmUtils.hs
index 55f9d6d551..36fb7ef6cb 100644
--- a/compiler/utils/AsmUtils.hs
+++ b/compiler/utils/AsmUtils.hs
@@ -6,6 +6,8 @@ module AsmUtils
     ( sectionType
     ) where
 
+import GhcPrelude
+
 import Platform
 import Outputable
 
diff --git a/compiler/utils/Bag.hs b/compiler/utils/Bag.hs
index fffbb6eb12..a027db23b7 100644
--- a/compiler/utils/Bag.hs
+++ b/compiler/utils/Bag.hs
@@ -25,6 +25,8 @@ module Bag (
         anyBagM, filterBagM
     ) where
 
+import GhcPrelude
+
 import Outputable
 import Util
 
diff --git a/compiler/utils/Binary.hs b/compiler/utils/Binary.hs
index 9254e97985..1c0284a332 100644
--- a/compiler/utils/Binary.hs
+++ b/compiler/utils/Binary.hs
@@ -59,6 +59,8 @@ module Binary
 -- The *host* architecture version:
 #include "../includes/MachDeps.h"
 
+import GhcPrelude
+
 import {-# SOURCE #-} Name (Name)
 import FastString
 import Panic
diff --git a/compiler/utils/BooleanFormula.hs b/compiler/utils/BooleanFormula.hs
index 43a71f0080..a42bb90a1c 100644
--- a/compiler/utils/BooleanFormula.hs
+++ b/compiler/utils/BooleanFormula.hs
@@ -16,6 +16,8 @@ module BooleanFormula (
         pprBooleanFormula, pprBooleanFormulaNice
   ) where
 
+import GhcPrelude
+
 import Data.List ( nub, intersperse )
 import Data.Data
 
diff --git a/compiler/utils/BufWrite.hs b/compiler/utils/BufWrite.hs
index eff57059de..e25bf06c4c 100644
--- a/compiler/utils/BufWrite.hs
+++ b/compiler/utils/BufWrite.hs
@@ -23,6 +23,8 @@ module BufWrite (
         bFlush,
   ) where
 
+import GhcPrelude
+
 import FastString
 import FastMutInt
 
diff --git a/compiler/utils/Digraph.hs b/compiler/utils/Digraph.hs
index 3d9e5a39cb..c6f2706cec 100644
--- a/compiler/utils/Digraph.hs
+++ b/compiler/utils/Digraph.hs
@@ -40,6 +40,8 @@ module Digraph(
 ------------------------------------------------------------------------------
 
 
+import GhcPrelude
+
 import Util        ( minWith, count )
 import Outputable
 import Maybes      ( expectJust )
diff --git a/compiler/utils/Encoding.hs b/compiler/utils/Encoding.hs
index f2b0979995..f809ba9016 100644
--- a/compiler/utils/Encoding.hs
+++ b/compiler/utils/Encoding.hs
@@ -33,6 +33,8 @@ module Encoding (
         toBase62Padded
   ) where
 
+import GhcPrelude
+
 import Foreign
 import Foreign.ForeignPtr.Unsafe
 import Data.Char
diff --git a/compiler/utils/EnumSet.hs b/compiler/utils/EnumSet.hs
index aa36b788aa..99b93f5c22 100644
--- a/compiler/utils/EnumSet.hs
+++ b/compiler/utils/EnumSet.hs
@@ -10,6 +10,8 @@ module EnumSet
     , empty
     ) where
 
+import GhcPrelude
+
 import qualified Data.IntSet as IntSet
 
 newtype EnumSet a = EnumSet IntSet.IntSet
diff --git a/compiler/utils/Exception.hs b/compiler/utils/Exception.hs
index 850393e359..9d9b3ae25c 100644
--- a/compiler/utils/Exception.hs
+++ b/compiler/utils/Exception.hs
@@ -6,6 +6,8 @@ module Exception
     )
     where
 
+import GhcPrelude
+
 import Control.Exception
 import Control.Monad.IO.Class
 
diff --git a/compiler/utils/FV.hs b/compiler/utils/FV.hs
index b5cf096aac..6d0dc2b2ab 100644
--- a/compiler/utils/FV.hs
+++ b/compiler/utils/FV.hs
@@ -26,6 +26,8 @@ module FV (
         mapUnionFV,
     ) where
 
+import GhcPrelude
+
 import Var
 import VarSet
 
diff --git a/compiler/utils/FastFunctions.hs b/compiler/utils/FastFunctions.hs
index c643e3c8fb..be3f3cbee4 100644
--- a/compiler/utils/FastFunctions.hs
+++ b/compiler/utils/FastFunctions.hs
@@ -10,6 +10,8 @@ module FastFunctions (
 
 #include "HsVersions.h"
 
+import GhcPrelude ()
+
 import GHC.Exts
 import GHC.IO   (IO(..))
 
diff --git a/compiler/utils/FastMutInt.hs b/compiler/utils/FastMutInt.hs
index 2a6e7b83aa..6ba139a486 100644
--- a/compiler/utils/FastMutInt.hs
+++ b/compiler/utils/FastMutInt.hs
@@ -15,6 +15,8 @@ module FastMutInt(
         readFastMutPtr, writeFastMutPtr
   ) where
 
+import GhcPrelude
+
 import Data.Bits
 import GHC.Base
 import GHC.Ptr
diff --git a/compiler/utils/FastString.hs b/compiler/utils/FastString.hs
index ee6dd7a415..fde4ff01de 100644
--- a/compiler/utils/FastString.hs
+++ b/compiler/utils/FastString.hs
@@ -97,6 +97,8 @@ module FastString
 
 #include "HsVersions.h"
 
+import GhcPrelude as Prelude
+
 import Encoding
 import FastFunctions
 import Panic
diff --git a/compiler/utils/FastStringEnv.hs b/compiler/utils/FastStringEnv.hs
index 14b0859211..1b4af6cee7 100644
--- a/compiler/utils/FastStringEnv.hs
+++ b/compiler/utils/FastStringEnv.hs
@@ -27,6 +27,8 @@ module FastStringEnv (
         mkDFsEnv, emptyDFsEnv, dFsEnvElts, lookupDFsEnv
     ) where
 
+import GhcPrelude
+
 import UniqFM
 import UniqDFM
 import Maybes
diff --git a/compiler/utils/Fingerprint.hsc b/compiler/utils/Fingerprint.hsc
index d4cee0e10b..4c89ec0893 100644
--- a/compiler/utils/Fingerprint.hsc
+++ b/compiler/utils/Fingerprint.hsc
@@ -24,6 +24,8 @@ module Fingerprint (
 #include "md5.h"
 ##include "HsVersions.h"
 
+import GhcPrelude
+
 import Foreign
 import GHC.IO
 import Numeric          ( readHex )
diff --git a/compiler/utils/FiniteMap.hs b/compiler/utils/FiniteMap.hs
index cb6e5573e8..afa3636432 100644
--- a/compiler/utils/FiniteMap.hs
+++ b/compiler/utils/FiniteMap.hs
@@ -7,6 +7,8 @@ module FiniteMap (
         foldRight, foldRightWithKey
     ) where
 
+import GhcPrelude
+
 import Data.Map (Map)
 import qualified Data.Map as Map
 
diff --git a/compiler/utils/GhcPrelude.hs b/compiler/utils/GhcPrelude.hs
new file mode 100644
index 0000000000..ed4eacbfb8
--- /dev/null
+++ b/compiler/utils/GhcPrelude.hs
@@ -0,0 +1,9 @@
+-- | Custom GHC "Prelude"
+--
+-- This module serves as a replacement for the "Prelude" module
+-- and abstracts over differences between the bootstrapping
+-- GHC version, and may also provide a common default vocabulary.
+--
+module GhcPrelude (module X) where
+
+import Prelude as X
diff --git a/compiler/utils/GraphBase.hs b/compiler/utils/GraphBase.hs
index c3850dfdd6..b66599356e 100644
--- a/compiler/utils/GraphBase.hs
+++ b/compiler/utils/GraphBase.hs
@@ -12,6 +12,8 @@ module GraphBase (
 
 where
 
+import GhcPrelude
+
 import UniqSet
 import UniqFM
 
diff --git a/compiler/utils/GraphColor.hs b/compiler/utils/GraphColor.hs
index be7975b306..7affb92391 100644
--- a/compiler/utils/GraphColor.hs
+++ b/compiler/utils/GraphColor.hs
@@ -12,6 +12,8 @@ module GraphColor (
 
 where
 
+import GhcPrelude
+
 import GraphBase
 import GraphOps
 import GraphPpr
diff --git a/compiler/utils/GraphOps.hs b/compiler/utils/GraphOps.hs
index 565134be92..bb4504ff1f 100644
--- a/compiler/utils/GraphOps.hs
+++ b/compiler/utils/GraphOps.hs
@@ -18,6 +18,8 @@ module GraphOps (
 )
 where
 
+import GhcPrelude
+
 import GraphBase
 
 import Outputable
diff --git a/compiler/utils/GraphPpr.hs b/compiler/utils/GraphPpr.hs
index a40e1058d0..c39395eda8 100644
--- a/compiler/utils/GraphPpr.hs
+++ b/compiler/utils/GraphPpr.hs
@@ -7,6 +7,8 @@ module GraphPpr (
 )
 where
 
+import GhcPrelude
+
 import GraphBase
 
 import Outputable
diff --git a/compiler/utils/IOEnv.hs b/compiler/utils/IOEnv.hs
index 6fc5f9dc67..b9210702fa 100644
--- a/compiler/utils/IOEnv.hs
+++ b/compiler/utils/IOEnv.hs
@@ -29,6 +29,8 @@ module IOEnv (
         atomicUpdMutVar, atomicUpdMutVar'
   ) where
 
+import GhcPrelude
+
 import DynFlags
 import Exception
 import Module
diff --git a/compiler/utils/Json.hs b/compiler/utils/Json.hs
index ffbff50641..2bf00d3851 100644
--- a/compiler/utils/Json.hs
+++ b/compiler/utils/Json.hs
@@ -1,6 +1,8 @@
 {-# LANGUAGE GADTs #-}
 module Json where
 
+import GhcPrelude
+
 import Outputable
 import Data.Char
 import Numeric
diff --git a/compiler/utils/ListSetOps.hs b/compiler/utils/ListSetOps.hs
index 7fa441402c..c311ac9c85 100644
--- a/compiler/utils/ListSetOps.hs
+++ b/compiler/utils/ListSetOps.hs
@@ -23,6 +23,8 @@ module ListSetOps (
 
 #include "HsVersions.h"
 
+import GhcPrelude
+
 import Outputable
 import Util
 
diff --git a/compiler/utils/ListT.hs b/compiler/utils/ListT.hs
index 7dc1aa3eaf..c16701419d 100644
--- a/compiler/utils/ListT.hs
+++ b/compiler/utils/ListT.hs
@@ -29,6 +29,8 @@ module ListT (
     fold
   ) where
 
+import GhcPrelude
+
 import Control.Applicative
 
 import Control.Monad
diff --git a/compiler/utils/Maybes.hs b/compiler/utils/Maybes.hs
index 89dd5b4fae..3a139a5b36 100644
--- a/compiler/utils/Maybes.hs
+++ b/compiler/utils/Maybes.hs
@@ -23,6 +23,8 @@ module Maybes (
         MaybeT(..), liftMaybeT, tryMaybeT
     ) where
 
+import GhcPrelude
+
 import Control.Monad
 import Control.Monad.Trans.Maybe
 import Control.Exception (catch, SomeException(..))
diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index d6fb31731e..39a76e1cf2 100644
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -27,6 +27,8 @@ module MonadUtils
 -- Imports
 -------------------------------------------------------------------------------
 
+import GhcPrelude
+
 import Maybes
 
 import Control.Monad
diff --git a/compiler/utils/OrdList.hs b/compiler/utils/OrdList.hs
index 90fdefb908..081210a534 100644
--- a/compiler/utils/OrdList.hs
+++ b/compiler/utils/OrdList.hs
@@ -15,6 +15,8 @@ module OrdList (
         mapOL, fromOL, toOL, foldrOL, foldlOL
 ) where
 
+import GhcPrelude
+
 import Outputable
 
 import Data.Semigroup   ( Semigroup )
diff --git a/compiler/utils/Outputable.hs b/compiler/utils/Outputable.hs
index 5cd7656b4f..d257e3ec9f 100644
--- a/compiler/utils/Outputable.hs
+++ b/compiler/utils/Outputable.hs
@@ -85,6 +85,8 @@ module Outputable (
         pprDebugAndThen, callStackDoc
     ) where
 
+import GhcPrelude
+
 import {-# SOURCE #-}   DynFlags( DynFlags, hasPprDebug, hasNoDebugOutput,
                                   targetPlatform, pprUserLength, pprCols,
                                   useUnicode, useUnicodeSyntax,
diff --git a/compiler/utils/Outputable.hs-boot b/compiler/utils/Outputable.hs-boot
index 980c186889..ad7d091833 100644
--- a/compiler/utils/Outputable.hs-boot
+++ b/compiler/utils/Outputable.hs-boot
@@ -1,5 +1,7 @@
 module Outputable where
 
+import GhcPrelude
+
 data SDoc
 
 showSDocUnsafe :: SDoc -> String
diff --git a/compiler/utils/Pair.hs b/compiler/utils/Pair.hs
index aeb8648b64..08b19be0b2 100644
--- a/compiler/utils/Pair.hs
+++ b/compiler/utils/Pair.hs
@@ -9,6 +9,8 @@ module Pair ( Pair(..), unPair, toPair, swap, pLiftFst, pLiftSnd ) where
 
 #include "HsVersions.h"
 
+import GhcPrelude
+
 import Outputable
 import qualified Data.Semigroup as Semi
 
diff --git a/compiler/utils/Panic.hs b/compiler/utils/Panic.hs
index 0a21f251fb..910906e08c 100644
--- a/compiler/utils/Panic.hs
+++ b/compiler/utils/Panic.hs
@@ -27,6 +27,8 @@ module Panic (
 ) where
 #include "HsVersions.h"
 
+import GhcPrelude
+
 import {-# SOURCE #-} Outputable (SDoc, showSDocUnsafe)
 
 import Config
diff --git a/compiler/utils/Platform.hs b/compiler/utils/Platform.hs
index 8cd1fa75e3..c313870f2f 100644
--- a/compiler/utils/Platform.hs
+++ b/compiler/utils/Platform.hs
@@ -20,6 +20,8 @@ module Platform (
 
 where
 
+import GhcPrelude
+
 -- | Contains enough information for the native code generator to emit
 --      code for this platform.
 data Platform
diff --git a/compiler/utils/PprColour.hs b/compiler/utils/PprColour.hs
index f8ea28faa9..f32b8b0084 100644
--- a/compiler/utils/PprColour.hs
+++ b/compiler/utils/PprColour.hs
@@ -1,4 +1,6 @@
 module PprColour where
+import GhcPrelude
+
 import Data.Maybe (fromMaybe)
 import Util (OverridingBool(..), split)
 import Data.Semigroup as Semi
diff --git a/compiler/utils/Pretty.hs b/compiler/utils/Pretty.hs
index a4d67f03a0..78c8e6a885 100644
--- a/compiler/utils/Pretty.hs
+++ b/compiler/utils/Pretty.hs
@@ -111,11 +111,12 @@ module Pretty (
 
   ) where
 
+import GhcPrelude hiding (error)
+
 import BufWrite
 import FastString
 import Panic
 import System.IO
-import Prelude hiding (error)
 
 --for a RULES
 import GHC.Base ( unpackCString# )
diff --git a/compiler/utils/State.hs b/compiler/utils/State.hs
index 8eca4657df..11bd7686d7 100644
--- a/compiler/utils/State.hs
+++ b/compiler/utils/State.hs
@@ -2,6 +2,8 @@
 
 module State where
 
+import GhcPrelude
+
 newtype State s a = State { runState' :: s -> (# a, s #) }
 
 instance Functor (State s) where
diff --git a/compiler/utils/Stream.hs b/compiler/utils/Stream.hs
index f7b21017cf..ad01fad40c 100644
--- a/compiler/utils/Stream.hs
+++ b/compiler/utils/Stream.hs
@@ -11,6 +11,8 @@ module Stream (
     Stream.map, Stream.mapM, Stream.mapAccumL
   ) where
 
+import GhcPrelude
+
 import Control.Monad
 
 -- |
diff --git a/compiler/utils/StringBuffer.hs b/compiler/utils/StringBuffer.hs
index d75e537fca..08402101af 100644
--- a/compiler/utils/StringBuffer.hs
+++ b/compiler/utils/StringBuffer.hs
@@ -45,6 +45,8 @@ module StringBuffer
 
 #include "HsVersions.h"
 
+import GhcPrelude
+
 import Encoding
 import FastString
 import FastFunctions
diff --git a/compiler/utils/UnVarGraph.hs b/compiler/utils/UnVarGraph.hs
index 228f3b5220..a540132bb7 100644
--- a/compiler/utils/UnVarGraph.hs
+++ b/compiler/utils/UnVarGraph.hs
@@ -27,6 +27,8 @@ module UnVarGraph
     , delNode
     ) where
 
+import GhcPrelude
+
 import Id
 import VarEnv
 import UniqFM
diff --git a/compiler/utils/UniqDFM.hs b/compiler/utils/UniqDFM.hs
index cb3dd7b7bd..715600ddb8 100644
--- a/compiler/utils/UniqDFM.hs
+++ b/compiler/utils/UniqDFM.hs
@@ -59,6 +59,8 @@ module UniqDFM (
         alwaysUnsafeUfmToUdfm,
     ) where
 
+import GhcPrelude
+
 import Unique           ( Uniquable(..), Unique, getKey )
 import Outputable
 
diff --git a/compiler/utils/UniqDSet.hs b/compiler/utils/UniqDSet.hs
index eef545eedd..e33becf036 100644
--- a/compiler/utils/UniqDSet.hs
+++ b/compiler/utils/UniqDSet.hs
@@ -32,6 +32,8 @@ module UniqDSet (
         partitionUniqDSet
     ) where
 
+import GhcPrelude
+
 import UniqDFM
 import UniqSet
 import Unique
diff --git a/compiler/utils/UniqFM.hs b/compiler/utils/UniqFM.hs
index 076479f984..f0cc197b71 100644
--- a/compiler/utils/UniqFM.hs
+++ b/compiler/utils/UniqFM.hs
@@ -71,6 +71,8 @@ module UniqFM (
         pprUniqFM, pprUFM, pprUFMWithKeys, pluralUFM
     ) where
 
+import GhcPrelude
+
 import Unique           ( Uniquable(..), Unique, getKey )
 import Outputable
 
diff --git a/compiler/utils/UniqMap.hs b/compiler/utils/UniqMap.hs
index c0960dd5b2..2dd3cd57ea 100644
--- a/compiler/utils/UniqMap.hs
+++ b/compiler/utils/UniqMap.hs
@@ -44,6 +44,8 @@ module UniqMap (
     -- Non-deterministic functions omitted
 ) where
 
+import GhcPrelude
+
 import UniqFM
 
 import Unique
diff --git a/compiler/utils/UniqSet.hs b/compiler/utils/UniqSet.hs
index d09b337d12..be600a09b3 100644
--- a/compiler/utils/UniqSet.hs
+++ b/compiler/utils/UniqSet.hs
@@ -46,6 +46,8 @@ module UniqSet (
         nonDetFoldUniqSet_Directly
     ) where
 
+import GhcPrelude
+
 import UniqFM
 import Unique
 import Data.Coerce
diff --git a/compiler/utils/Util.hs b/compiler/utils/Util.hs
index 6146bf0113..3b402f2833 100644
--- a/compiler/utils/Util.hs
+++ b/compiler/utils/Util.hs
@@ -129,6 +129,8 @@ module Util (
 
 #include "HsVersions.h"
 
+import GhcPrelude
+
 import Exception
 import Panic