Extract out use of UnboxedTuples from GHCi.Leak

See #13101 + #15454 for motivation.  This change reduces the number of
modules that need to be compiled to object code when loading GHC into
GHCi.

2 files changed, 19 insertions, 5 deletions

diff --git a/ghc/GHCi/Leak.hs b/ghc/GHCi/Leak.hs
index 8135c3731e..874d9e2cdc 100644
--- a/ghc/GHCi/Leak.hs
+++ b/ghc/GHCi/Leak.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE RecordWildCards, LambdaCase, MagicHash, UnboxedTuples #-}
+{-# LANGUAGE RecordWildCards, LambdaCase #-}
 module GHCi.Leak
   ( LeakIndicators
   , getLeakIndicators
@@ -10,9 +10,8 @@ import Data.Bits
 import DynFlags ( sTargetPlatform )
 import Foreign.Ptr (ptrToIntPtr, intPtrToPtr)
 import GHC
-import GHC.Exts (anyToAddr#)
 import GHC.Ptr (Ptr (..))
-import GHC.Types (IO (..))
+import GHCi.Util
 import HscTypes
 import Outputable
 import Platform (target32Bit)
@@ -64,8 +63,7 @@ checkLeakIndicators dflags (LeakIndicators leakmods)  = do
   report :: String -> Maybe a -> IO ()
   report _ Nothing = return ()
   report msg (Just a) = do
-    addr <- IO (\s -> case anyToAddr# a s of
-                        (# s', addr #) -> (# s', Ptr addr #)) :: IO (Ptr ())
+    addr <- anyToPtr a
     putStrLn ("-fghci-leak-check: " ++ msg ++ " is still alive at " ++
               show (maskTagBits addr))
 
diff --git a/ghc/GHCi/Util.hs b/ghc/GHCi/Util.hs
new file mode 100644
index 0000000000..050a0566d6
--- /dev/null
+++ b/ghc/GHCi/Util.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE MagicHash, UnboxedTuples #-}
+
+-- | Utilities for GHCi.
+module GHCi.Util where
+
+-- NOTE: Avoid importing GHC modules here, because the primary purpose
+-- of this module is to not use UnboxedTuples in a module that imports
+-- lots of other modules.  See issue#13101 for more info.
+
+import GHC.Exts
+import GHC.Types
+
+anyToPtr :: a -> IO (Ptr ())
+anyToPtr x =
+  IO (\s -> case anyToAddr# x s of
+              (# s', addr #) -> (# s', Ptr addr #)) :: IO (Ptr ())