Don't perform permission checks for scripts named with -ghci-script (#6017)

The user explicitly requested this script on the command-line, so it's
unnecessary to require that the script is also owned by the user.
Also, it is currently impossible to make a GHCi wrapper that invokes a
custom script without first making a copy of the script to circumvent
the permissions check, which seems wrong.

ghc/InteractiveUI.hs

@@ -455,13 +455,18 @@ runGHCi paths maybe_exprs = do
    canonicalizePath' fp = liftM Just (canonicalizePath fp)
                 `catchIO` \_ -> return Nothing
 
-   sourceConfigFile :: FilePath -> GHCi ()
-   sourceConfigFile file = do
+   sourceConfigFile :: (FilePath, Bool) -> GHCi ()
+   sourceConfigFile (file, check_perms) = do
      exists <- liftIO $ doesFileExist file
      when exists $ do
-       dir_ok  <- liftIO $ checkPerms (getDirectory file)
-       file_ok <- liftIO $ checkPerms file
-       when (dir_ok && file_ok) $ do
+       perms_ok <-
+         if not check_perms
+            then return True
+            else do
+              dir_ok  <- liftIO $ checkPerms (getDirectory file)
+              file_ok <- liftIO $ checkPerms file
+              return (dir_ok && file_ok)
+       when perms_ok $ do
          either_hdl <- liftIO $ tryIO (openFile file ReadMode)
          case either_hdl of
            Left _e   -> return ()
@@ -479,9 +484,14 @@ runGHCi paths maybe_exprs = do
   setGHCContextFromGHCiState
 
   when (read_dot_files) $ do
-    mcfgs0 <- sequence $ [ current_dir, app_user_dir, home_dir ] ++ map (return . Just ) (ghciScripts dflags)
-    mcfgs <- liftIO $ mapM canonicalizePath' (catMaybes mcfgs0)
-    mapM_ sourceConfigFile $ nub $ catMaybes mcfgs
+    mcfgs0 <- catMaybes <$> sequence [ current_dir, app_user_dir, home_dir ]
+    let mcfgs1 = zip mcfgs0 (repeat True)
+              ++ zip (ghciScripts dflags) (repeat False)
+         -- False says "don't check permissions".  We don't
+         -- require that a script explicitly added by
+         -- -ghci-script is owned by the current user. (#6017)
+    mcfgs <- liftIO $ mapM (\(f, b) -> (,b) <$> canonicalizePath' f) mcfgs1
+    mapM_ sourceConfigFile $ nub $ [ (f,b) | (Just f, b) <- mcfgs ]
         -- nub, because we don't want to read .ghci twice if the
         -- CWD is $HOME.
 

ghc/ghc-bin.cabal.in

@@ -48,6 +48,7 @@ Executable ghc
         Extensions: ForeignFunctionInterface,
                     UnboxedTuples,
                     FlexibleInstances,
+                    TupleSections,
                     MagicHash
 
     Extensions: CPP, PatternGuards, NondecreasingIndentation