From 30ccf9ed1f592531dac9f3d750278fac6303c3e4 Mon Sep 17 00:00:00 2001
From: Joachim Breitner <mail@joachim-breitner.de>
Date: Wed, 10 Mar 2021 15:28:40 -0500
Subject: Introduce GHC2021 language

This adds support for -XGHC2021, as described in Proposal 0380 [1].

[1] https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0380-ghc2021.rst
---
 compiler/GHC/Driver/Flags.hs   |  2 +-
 compiler/GHC/Driver/Session.hs | 53 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 2 deletions(-)

(limited to 'compiler')

diff --git a/compiler/GHC/Driver/Flags.hs b/compiler/GHC/Driver/Flags.hs
index 3a31e55ff1..2b86c0f266 100644
--- a/compiler/GHC/Driver/Flags.hs
+++ b/compiler/GHC/Driver/Flags.hs
@@ -534,7 +534,7 @@ instance ToJson WarnReason where
   json (ErrReason (Just wf)) = JSString (show wf)
 
 
-data Language = Haskell98 | Haskell2010
+data Language = Haskell98 | Haskell2010 | GHC2021
    deriving (Eq, Enum, Show, Bounded)
 
 instance Outputable Language where
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index 8b7ddd321d..b4218d29ba 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -1351,6 +1351,56 @@ languageExtensions (Just Haskell2010)
        LangExt.FieldSelectors,
        LangExt.RelaxedPolyRec]
 
+languageExtensions (Just GHC2021)
+    = [LangExt.ImplicitPrelude,
+       -- See Note [When is StarIsType enabled]
+       LangExt.StarIsType,
+       LangExt.MonomorphismRestriction,
+       LangExt.TraditionalRecordSyntax,
+       LangExt.EmptyDataDecls,
+       LangExt.ForeignFunctionInterface,
+       LangExt.PatternGuards,
+       LangExt.DoAndIfThenElse,
+       LangExt.FieldSelectors,
+       LangExt.RelaxedPolyRec,
+       -- Now the new extensions (not in Haskell2010)
+       LangExt.BangPatterns,
+       LangExt.BinaryLiterals,
+       LangExt.ConstrainedClassMethods,
+       LangExt.ConstraintKinds,
+       LangExt.DeriveDataTypeable,
+       LangExt.DeriveFoldable,
+       LangExt.DeriveFunctor,
+       LangExt.DeriveGeneric,
+       LangExt.DeriveLift,
+       LangExt.DeriveTraversable,
+       LangExt.EmptyCase,
+       LangExt.EmptyDataDeriving,
+       LangExt.ExistentialQuantification,
+       LangExt.ExplicitForAll,
+       LangExt.FlexibleContexts,
+       LangExt.FlexibleInstances,
+       LangExt.GADTSyntax,
+       LangExt.GeneralizedNewtypeDeriving,
+       LangExt.HexFloatLiterals,
+       LangExt.ImportQualifiedPost,
+       LangExt.InstanceSigs,
+       LangExt.KindSignatures,
+       LangExt.MultiParamTypeClasses,
+       LangExt.RecordPuns,
+       LangExt.NamedWildCards,
+       LangExt.NumericUnderscores,
+       LangExt.PolyKinds,
+       LangExt.PostfixOperators,
+       LangExt.RankNTypes,
+       LangExt.ScopedTypeVariables,
+       LangExt.StandaloneDeriving,
+       LangExt.StandaloneKindSignatures,
+       LangExt.TupleSections,
+       LangExt.TypeApplications,
+       LangExt.TypeOperators,
+       LangExt.TypeSynonymInstances]
+
 hasPprDebug :: DynFlags -> Bool
 hasPprDebug = dopt Opt_D_ppr_debug
 
@@ -3401,7 +3451,8 @@ supportedLanguagesAndExtensions arch_os =
 languageFlagsDeps :: [(Deprecation, FlagSpec Language)]
 languageFlagsDeps = [
   flagSpec "Haskell98"   Haskell98,
-  flagSpec "Haskell2010" Haskell2010
+  flagSpec "Haskell2010" Haskell2010,
+  flagSpec "GHC2021"     GHC2021
   ]
 
 -- | These -X<blah> flags cannot be reversed with -XNo<blah>
-- 
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