Always enable the external interpreter

You can always just not use or even build `iserv`. I don't think the
maintenance cost of the CPP is worth...I can't even tell what the
benefit is.

13 files changed, 46 insertions, 126 deletions

diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index f191370071..a612733de6 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -25,11 +25,6 @@ Flag ghci
     Default: False
     Manual: True
 
-Flag ext-interp
-    Description: Support external interpreter
-    Default: True
-    Manual: True
-
 Flag stage1
     Description: Is this stage 1?
     Default: False
@@ -98,12 +93,6 @@ Library
         CPP-Options: -DHAVE_INTERNAL_INTERPRETER
         Include-Dirs: ../rts/dist/build @FFIIncludeDir@
 
-    if flag(ext-interp)
-        CPP-Options: -DHAVE_EXTERNAL_INTERPRETER
-
-    if flag(ghci) || flag(ext-interp)
-        CPP-Options: -DHAVE_INTERPRETER
-
     -- sanity-check to ensure not more than one integer flag is set
     if flag(integer-gmp) && flag(integer-simple)
         build-depends: invalid-cabal-flag-settings<0
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 9e9e70ad28..465dd2737b 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -4360,26 +4360,25 @@ supportedLanguages = map (flagSpecName . snd) languageFlagsDeps
 supportedLanguageOverlays :: [String]
 supportedLanguageOverlays = map (flagSpecName . snd) safeHaskellFlagsDeps
 
-supportedExtensions :: [String]
-supportedExtensions = concatMap toFlagSpecNamePair xFlags
+supportedExtensions :: PlatformMini -> [String]
+supportedExtensions targetPlatformMini = concatMap toFlagSpecNamePair xFlags
   where
     toFlagSpecNamePair flg
-#if !defined(HAVE_INTERPRETER)
       -- IMPORTANT! Make sure that `ghc --supported-extensions` omits
       -- "TemplateHaskell"/"QuasiQuotes" when it's known not to work out of the
       -- box. See also GHC #11102 and #16331 for more details about
       -- the rationale
-      | flagSpecFlag flg == LangExt.TemplateHaskell  = [noName]
-      | flagSpecFlag flg == LangExt.QuasiQuotes      = [noName]
-#endif
+      | isAIX, flagSpecFlag flg == LangExt.TemplateHaskell  = [noName]
+      | isAIX, flagSpecFlag flg == LangExt.QuasiQuotes      = [noName]
       | otherwise = [name, noName]
       where
+        isAIX = platformMini_os targetPlatformMini == OSAIX
         noName = "No" ++ name
         name = flagSpecName flg
 
-supportedLanguagesAndExtensions :: [String]
-supportedLanguagesAndExtensions =
-    supportedLanguages ++ supportedLanguageOverlays ++ supportedExtensions
+supportedLanguagesAndExtensions :: PlatformMini -> [String]
+supportedLanguagesAndExtensions targetPlatformMini =
+    supportedLanguages ++ supportedLanguageOverlays ++ supportedExtensions targetPlatformMini
 
 -- | These -X<blah> flags cannot be reversed with -XNo<blah>
 languageFlagsDeps :: [(Deprecation, FlagSpec Language)]
diff --git a/compiler/main/DynamicLoading.hs b/compiler/main/DynamicLoading.hs
index 64cc0a1216..ea09a8ceb5 100644
--- a/compiler/main/DynamicLoading.hs
+++ b/compiler/main/DynamicLoading.hs
@@ -3,7 +3,6 @@
 -- | Dynamically lookup up values from modules and loading them.
 module DynamicLoading (
         initializePlugins,
-#if defined(HAVE_INTERPRETER)
         -- * Loading plugins
         loadFrontendPlugin,
 
@@ -19,15 +18,11 @@ module DynamicLoading (
         getValueSafely,
         getHValueSafely,
         lessUnsafeCoerce
-#else
-        pluginError
-#endif
     ) where
 
 import GhcPrelude
 import DynFlags
 
-#if defined(HAVE_INTERPRETER)
 import Linker           ( linkModule, getHValue )
 import GHCi             ( wormhole )
 import SrcLoc           ( noSrcSpan )
@@ -60,28 +55,11 @@ import Control.Monad     ( when, unless )
 import Data.Maybe        ( mapMaybe )
 import GHC.Exts          ( unsafeCoerce# )
 
-#else
-
-import HscTypes         ( HscEnv )
-import Module           ( ModuleName, moduleNameString )
-import Panic
-
-import Data.List        ( intercalate )
-import Control.Monad    ( unless )
-
-#endif
-
 -- | Loads the plugins specified in the pluginModNames field of the dynamic
 -- flags. Should be called after command line arguments are parsed, but before
 -- actual compilation starts. Idempotent operation. Should be re-called if
 -- pluginModNames or pluginModNameOpts changes.
 initializePlugins :: HscEnv -> DynFlags -> IO DynFlags
-#if !defined(HAVE_INTERPRETER)
-initializePlugins _ df
-  = do let pluginMods = pluginModNames df
-       unless (null pluginMods) (pluginError pluginMods)
-       return df
-#else
 initializePlugins hsc_env df
   | map lpModuleName (cachedPlugins df)
          == pluginModNames df -- plugins not changed
@@ -93,10 +71,6 @@ initializePlugins hsc_env df
   = do loadedPlugins <- loadPlugins (hsc_env { hsc_dflags = df })
        return $ df { cachedPlugins = loadedPlugins }
   where argumentsForPlugin p = map snd . filter ((== lpModuleName p) . fst)
-#endif
-
-
-#if defined(HAVE_INTERPRETER)
 
 loadPlugins :: HscEnv -> IO [LoadedPlugin]
 loadPlugins hsc_env
@@ -302,15 +276,3 @@ throwCmdLineErrorS dflags = throwCmdLineError . showSDoc dflags
 
 throwCmdLineError :: String -> IO a
 throwCmdLineError = throwGhcExceptionIO . CmdLineError
-
-#else
-
-pluginError :: [ModuleName] -> a
-pluginError modnames = throwGhcException (CmdLineError msg)
-  where
-    msg = "not built for interactive use - can't load plugins ("
-            -- module names are not z-encoded
-          ++ intercalate ", " (map moduleNameString modnames)
-          ++ ")"
-
-#endif
diff --git a/compiler/main/HeaderInfo.hs b/compiler/main/HeaderInfo.hs
index d534fab1d5..bd984618a4 100644
--- a/compiler/main/HeaderInfo.hs
+++ b/compiler/main/HeaderInfo.hs
@@ -22,6 +22,7 @@ module HeaderInfo ( getImports
 
 import GhcPrelude
 
+import GHC.Platform
 import HscTypes
 import Parser           ( parseHeader )
 import Lexer
@@ -306,10 +307,12 @@ checkExtension :: DynFlags -> Located FastString -> Located String
 checkExtension dflags (dL->L l ext)
 -- Checks if a given extension is valid, and if so returns
 -- its corresponding flag. Otherwise it throws an exception.
- =  let ext' = unpackFS ext in
-    if ext' `elem` supportedLanguagesAndExtensions
+  = if ext' `elem` supported
     then cL l ("-X"++ext')
     else unsupportedExtnError dflags l ext'
+  where
+    ext' = unpackFS ext
+    supported = supportedLanguagesAndExtensions $ platformMini $ targetPlatform dflags
 
 languagePragParseError :: DynFlags -> SrcSpan -> a
 languagePragParseError dflags loc =
@@ -325,7 +328,8 @@ unsupportedExtnError dflags loc unsup =
         text "Unsupported extension: " <> text unsup $$
         if null suggestions then Outputable.empty else text "Perhaps you meant" <+> quotedListWithOr (map text suggestions)
   where
-     suggestions = fuzzyMatch unsup supportedLanguagesAndExtensions
+     supported = supportedLanguagesAndExtensions $ platformMini $ targetPlatform dflags
+     suggestions = fuzzyMatch unsup supported
 
 
 optionsErrorMsgs :: DynFlags -> [String] -> [Located String] -> FilePath -> Messages
diff --git a/compiler/rename/RnExpr.hs b/compiler/rename/RnExpr.hs
index f2f0685159..3ec24a7a6d 100644
--- a/compiler/rename/RnExpr.hs
+++ b/compiler/rename/RnExpr.hs
@@ -211,8 +211,6 @@ rnExpr (NegApp _ e _)
 
 ------------------------------------------
 -- Template Haskell extensions
--- Don't ifdef-HAVE_INTERPRETER them because we want to fail gracefully
--- (not with an rnExpr crash) in a stage-1 compiler.
 rnExpr e@(HsBracket _ br_body) = rnBracket e br_body
 
 rnExpr (HsSpliceE _ splice) = rnSpliceExpr splice
diff --git a/compiler/simplCore/SimplCore.hs b/compiler/simplCore/SimplCore.hs
index 572084c420..b3af87b2af 100644
--- a/compiler/simplCore/SimplCore.hs
+++ b/compiler/simplCore/SimplCore.hs
@@ -462,11 +462,7 @@ doCorePass (CoreDoRuleCheck phase pat)  = ruleCheckPass phase pat
 doCorePass CoreDoNothing                = return
 doCorePass (CoreDoPasses passes)        = runCorePasses passes
 
-#if defined(HAVE_INTERPRETER)
 doCorePass (CoreDoPluginPass _ pass) = {-# SCC "Plugin" #-} pass
-#else
-doCorePass pass@CoreDoPluginPass {}  = pprPanic "doCorePass" (ppr pass)
-#endif
 
 doCorePass pass@CoreDesugar          = pprPanic "doCorePass" (ppr pass)
 doCorePass pass@CoreDesugarOpt       = pprPanic "doCorePass" (ppr pass)
diff --git a/compiler/typecheck/TcPluginM.hs b/compiler/typecheck/TcPluginM.hs
index 3785a4aac5..f4fe3013a3 100644
--- a/compiler/typecheck/TcPluginM.hs
+++ b/compiler/typecheck/TcPluginM.hs
@@ -3,7 +3,6 @@
 -- access select functions of the 'TcM', principally those to do with
 -- reading parts of the state.
 module TcPluginM (
-#if defined(HAVE_INTERPRETER)
         -- * Basic TcPluginM functionality
         TcPluginM,
         tcPluginIO,
@@ -49,10 +48,8 @@ module TcPluginM (
         newEvVar,
         setEvBind,
         getEvBindsTcPluginM
-#endif
     ) where
 
-#if defined(HAVE_INTERPRETER)
 import GhcPrelude
 
 import qualified TcRnMonad as TcM
@@ -190,7 +187,3 @@ setEvBind :: EvBind -> TcPluginM ()
 setEvBind ev_bind = do
     tc_evbinds <- getEvBindsTcPluginM
     unsafeTcPluginTcM $ TcM.addTcEvBind tc_evbinds ev_bind
-#else
--- this dummy import is needed as a consequence of NoImplicitPrelude
-import GhcPrelude ()
-#endif
diff --git a/ghc/Main.hs b/ghc/Main.hs
index d53c71a779..4cdf3ecb94 100644
--- a/ghc/Main.hs
+++ b/ghc/Main.hs
@@ -1,4 +1,7 @@
-{-# LANGUAGE CPP, NondecreasingIndentation, TupleSections #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE NondecreasingIndentation #-}
+{-# LANGUAGE TupleSections #-}
 {-# OPTIONS -fno-warn-incomplete-patterns -optc-DNON_POSIX_SOURCE #-}
 
 -----------------------------------------------------------------------------
@@ -30,12 +33,8 @@ import GHCi.UI          ( interactiveUI, ghciWelcomeMsg, defaultGhciSettings )
 #endif
 
 -- Frontend plugins
-#if defined(HAVE_INTERPRETER)
 import DynamicLoading   ( loadFrontendPlugin )
 import Plugins
-#else
-import DynamicLoading   ( pluginError )
-#endif
 #if defined(HAVE_INTERNAL_INTERPRETER)
 import DynamicLoading   ( initializePlugins )
 #endif
@@ -44,6 +43,8 @@ import Module           ( ModuleName )
 
 -- Various other random stuff that we need
 import GHC.HandleEncoding
+import GHC.Platform
+import GHC.Platform.Host
 import Config
 import Constants
 import HscTypes
@@ -54,6 +55,8 @@ import DynFlags hiding (WarnReason(..))
 import ErrUtils
 import FastString
 import Outputable
+import SysTools.BaseDir
+import SysTools.Settings
 import SrcLoc
 import Util
 import Panic
@@ -74,6 +77,8 @@ import System.Environment
 import System.Exit
 import System.FilePath
 import Control.Monad
+import Control.Monad.Trans.Class
+import Control.Monad.Trans.Except (throwE, runExceptT)
 import Data.Char
 import Data.List
 import Data.Maybe
@@ -122,7 +127,7 @@ main = do
     case mode of
         Left preStartupMode ->
             do case preStartupMode of
-                   ShowSupportedExtensions   -> showSupportedExtensions
+                   ShowSupportedExtensions   -> showSupportedExtensions mbMinusB
                    ShowVersion               -> showVersion
                    ShowNumVersion            -> putStrLn cProjectVersion
                    ShowOptions isInteractive -> showOptions isInteractive
@@ -776,8 +781,24 @@ showInfo dflags = do
         let sq x = " [" ++ x ++ "\n ]"
         putStrLn $ sq $ intercalate "\n ," $ map show $ compilerInfo dflags
 
-showSupportedExtensions :: IO ()
-showSupportedExtensions = mapM_ putStrLn supportedLanguagesAndExtensions
+-- TODO use ErrUtils once that is disentangled from all the other GhcMonad stuff?
+showSupportedExtensions :: Maybe String -> IO ()
+showSupportedExtensions m_top_dir = do
+  res <- runExceptT $ do
+    top_dir <- lift (tryFindTopDir m_top_dir) >>= \case
+      Nothing -> throwE $ SettingsError_MissingData "Could not find the top directory, missing -B flag"
+      Just dir -> pure dir
+    initSettings top_dir
+  targetPlatformMini <- case res of
+    Right s -> pure $ platformMini $ sTargetPlatform s
+    Left (SettingsError_MissingData msg) -> do
+      hPutStrLn stderr $ "WARNING: " ++ show msg
+      hPutStrLn stderr $ "cannot know target platform so guessing target == host (native compiler)."
+      pure cHostPlatformMini
+    Left (SettingsError_BadData msg) -> do
+      hPutStrLn stderr msg
+      exitWith $ ExitFailure 1
+  mapM_ putStrLn $ supportedLanguagesAndExtensions targetPlatformMini
 
 showVersion :: IO ()
 showVersion = putStrLn (cProjectName ++ ", version " ++ cProjectVersion)
@@ -847,15 +868,11 @@ dumpPackagesSimple dflags = putMsg dflags (pprPackagesSimple dflags)
 -- Frontend plugin support
 
 doFrontend :: ModuleName -> [(String, Maybe Phase)] -> Ghc ()
-#if !defined(HAVE_INTERPRETER)
-doFrontend modname _ = pluginError [modname]
-#else
 doFrontend modname srcs = do
     hsc_env <- getSession
     frontend_plugin <- liftIO $ loadFrontendPlugin hsc_env modname
     frontend frontend_plugin
       (reverse $ frontendPluginOpts (hsc_dflags hsc_env)) srcs
-#endif
 
 -- -----------------------------------------------------------------------------
 -- ABI hash support
diff --git a/ghc/ghc-bin.cabal.in b/ghc/ghc-bin.cabal.in
index cf5fde03e3..721df4ea62 100644
--- a/ghc/ghc-bin.cabal.in
+++ b/ghc/ghc-bin.cabal.in
@@ -24,11 +24,6 @@ Flag ghci
     Default: False
     Manual: True
 
-Flag ext-interp
-    Description: Build external interpreter support
-    Default: True
-    Manual: True
-
 Flag threaded
     Description: Link the ghc executable against the threaded RTS
     Default: True
@@ -44,6 +39,7 @@ Executable ghc
                    directory  >= 1   && < 1.4,
                    process    >= 1   && < 1.7,
                    filepath   >= 1   && < 1.5,
+                   transformers == 0.5.*,
                    ghc-boot   == @ProjectVersionMunged@,
                    ghc        == @ProjectVersionMunged@
 
@@ -66,8 +62,7 @@ Executable ghc
             ghc-prim       >= 0.5.0 && < 0.7,
             ghci           == @ProjectVersionMunged@,
             haskeline      == 0.7.*,
-            time           >= 1.8 && < 1.10,
-            transformers   == 0.5.*
+            time           >= 1.8 && < 1.10
         CPP-Options: -DHAVE_INTERNAL_INTERPRETER
         GHC-Options: -fno-warn-name-shadowing
         Other-Modules:
@@ -97,12 +92,6 @@ Executable ghc
     if flag(threaded)
       ghc-options: -threaded
 
-    if flag(ext-interp)
-      cpp-options: -DHAVE_EXTERNAL_INTERPRETER
-
-    if flag(ghci) || flag(ext-interp)
-      cpp-options: -DHAVE_INTERPRETER
-
     Other-Extensions:
         CPP
         NondecreasingIndentation
diff --git a/hadrian/src/Settings/Packages.hs b/hadrian/src/Settings/Packages.hs
index 98fe8a2e24..20bd114480 100644
--- a/hadrian/src/Settings/Packages.hs
+++ b/hadrian/src/Settings/Packages.hs
@@ -79,7 +79,6 @@ packageArgs = do
           , builder (Cabal Flags) ? mconcat
             [ ghcWithNativeCodeGen ? arg "ncg"
             , ghcWithInterpreter ? notStage0 ? arg "ghci"
-            , notStage0 ? not windowsHost ? notM cross ? arg "ext-interp"
             , cross ? arg "-terminfo"
             , notStage0 ? intLib == integerGmp ?
               arg "integer-gmp"
@@ -94,7 +93,6 @@ packageArgs = do
 
           , builder (Cabal Flags) ? mconcat
             [ ghcWithInterpreter ? notStage0 ? arg "ghci"
-            , notStage0 ? not windowsHost ? notM cross ? arg "ext-interp"
             , cross ? arg "-terminfo"
             -- the 'threaded' flag is True by default, but
             -- let's record explicitly that we link all ghc
@@ -128,8 +126,6 @@ packageArgs = do
         -- behind the @-fghci@ flag.
         , package ghci ? mconcat
           [ notStage0 ? builder (Cabal Flags) ? arg "ghci"
-          , notStage0 ? builder (Cabal Flags) ? not windowsHost ? notM cross
-                      ? arg "ext-interp"
           , cross ? stage0 ? builder (Cabal Flags) ? arg "ghci" ]
 
         -------------------------------- haddock -------------------------------
diff --git a/libraries/ghci/GHCi/BreakArray.hs b/libraries/ghci/GHCi/BreakArray.hs
index 41a2ab498f..8ab813a5a7 100644
--- a/libraries/ghci/GHCi/BreakArray.hs
+++ b/libraries/ghci/GHCi/BreakArray.hs
@@ -19,17 +19,14 @@
 module GHCi.BreakArray
     (
       BreakArray
-#if defined(HAVE_INTERPRETER)
           (BA) -- constructor is exported only for ByteCodeGen
     , newBreakArray
     , getBreak
     , setBreakOn
     , setBreakOff
     , showBreakArray
-#endif
     ) where
 
-#if defined(HAVE_INTERPRETER)
 import Prelude -- See note [Why do we import Prelude here?]
 import Control.Monad
 import Data.Word
@@ -116,6 +113,3 @@ readBA# array i = IO $ \s ->
 
 readBreakArray :: BreakArray -> Int -> IO Word8
 readBreakArray (BA array) (I# i) = readBA# array i
-#else
-data BreakArray
-#endif
diff --git a/libraries/ghci/GHCi/InfoTable.hsc b/libraries/ghci/GHCi/InfoTable.hsc
index 826e3bc2fd..ab13485e28 100644
--- a/libraries/ghci/GHCi/InfoTable.hsc
+++ b/libraries/ghci/GHCi/InfoTable.hsc
@@ -10,13 +10,10 @@
 --
 module GHCi.InfoTable
   (
-#if defined(HAVE_INTERPRETER)
     mkConInfoTable
-#endif
   ) where
 
 import Prelude -- See note [Why do we import Prelude here?]
-#if defined(HAVE_INTERPRETER)
 import Foreign
 import Foreign.C
 import GHC.Ptr
@@ -24,7 +21,6 @@ import GHC.Exts
 import GHC.Exts.Heap
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
-#endif
 
 ghciTablesNextToCode :: Bool
 #if defined(TABLES_NEXT_TO_CODE)
@@ -33,7 +29,6 @@ ghciTablesNextToCode = True
 ghciTablesNextToCode = False
 #endif
 
-#if defined(HAVE_INTERPRETER) /* To end */
 -- NOTE: Must return a pointer acceptable for use in the header of a closure.
 -- If tables_next_to_code is enabled, then it must point the the 'code' field.
 -- Otherwise, it should point to the start of the StgInfoTable.
@@ -387,4 +382,3 @@ wORD_SIZE = (#const SIZEOF_HSINT)
 
 conInfoTableSizeB :: Int
 conInfoTableSizeB = wORD_SIZE + itblSize
-#endif /* HAVE_INTERPRETER */
diff --git a/libraries/ghci/ghci.cabal.in b/libraries/ghci/ghci.cabal.in
index 4da94b3549..849e2a147a 100644
--- a/libraries/ghci/ghci.cabal.in
+++ b/libraries/ghci/ghci.cabal.in
@@ -22,11 +22,6 @@ Flag ghci
     Default: False
     Manual: True
 
-Flag ext-interp
-    Description: Build external interpreter support
-    Default: True
-    Manual: True
-
 source-repository head
     type:     git
     location: https://gitlab.haskell.org/ghc/ghc.git
@@ -61,12 +56,6 @@ library
             GHCi.Signals
             GHCi.TH
 
-    if flag(ext-interp)
-        CPP-Options: -DHAVE_EXTERNAL_INTERPRETER
-
-    if flag(ghci) || flag(ext-interp)
-        CPP-Options: -DHAVE_INTERPRETER
-
     include-dirs: @FFIIncludeDir@
 
     exposed-modules: