Initialise Settings before DynFlags

Stops us having to temporarily have a panic in the DynFlags.
We still need a panic in the DynFlags used for the top-level
error handler, though.

compiler/main/DynFlags.hs

@@ -43,7 +43,7 @@ module DynFlags (
 
 
         -- ** Manipulating DynFlags
-        defaultDynFlags,                -- DynFlags
+        defaultDynFlags,                -- Settings -> DynFlags
         initDynFlags,                   -- DynFlags -> IO DynFlags
 
         getOpts,                        -- DynFlags -> (DynFlags -> [a]) -> [a]
@@ -697,8 +697,8 @@ initDynFlags dflags = do
 
 -- | The normal 'DynFlags'. Note that they is not suitable for use in this form
 -- and must be fully initialized by 'GHC.newSession' first.
-defaultDynFlags :: DynFlags
-defaultDynFlags =
+defaultDynFlags :: Settings -> DynFlags
+defaultDynFlags mySettings =
      DynFlags {
         ghcMode                 = CompManager,
         ghcLink                 = LinkBinary,
@@ -774,8 +774,7 @@ defaultDynFlags =
         buildTag                = panic "defaultDynFlags: No buildTag",
         rtsBuildTag             = panic "defaultDynFlags: No rtsBuildTag",
         splitInfo               = Nothing,
-        -- initSysTools fills this in:
-        settings                = panic "defaultDynFlags: No settings",
+        settings                = mySettings,
         -- ghc -M values
         depMakefile       = "Makefile",
         depIncludePkgDeps = False,

compiler/main/GHC.hs

@@ -431,9 +431,8 @@ initGhcMonad mb_top_dir = do
 
   liftIO $ StaticFlags.initStaticOpts
 
-  dflags0 <- liftIO $ initDynFlags defaultDynFlags
   mySettings <- liftIO $ initSysTools mb_top_dir
-  let dflags = dflags0 { settings = mySettings }
+  dflags <- liftIO $ initDynFlags (defaultDynFlags mySettings)
   env <- liftIO $ newHscEnv dflags
   setSession env
 

ghc/Main.hs

@@ -78,7 +78,8 @@ import Data.Maybe
 main :: IO ()
 main = do
    hSetBuffering stdout NoBuffering
-   GHC.defaultErrorHandler defaultDynFlags $ do
+   let defaultErrorHandlerDynFlags = defaultDynFlags (panic "No settings")
+   GHC.defaultErrorHandler defaultErrorHandlerDynFlags $ do
     -- 1. extract the -B flag from the args
     argv0 <- getArgs
 

utils/ghctags/Main.hs

@@ -10,6 +10,7 @@ import DriverPhases     ( isHaskellSrcFilename )
 import HscTypes         ( msHsFilePath )
 import Name             ( getOccString )
 --import ErrUtils         ( printBagOfErrors )
+import Panic            ( panic )
 import DynFlags         ( defaultDynFlags )
 import Bag
 import Exception
@@ -100,7 +101,7 @@ main = do
                      then Just `liftM` openFile "TAGS" openFileMode
                      else return Nothing
 
-  GHC.defaultErrorHandler defaultDynFlags $
+  GHC.defaultErrorHandler (defaultDynFlags (panic "No settings")) $
     runGhc (Just ghc_topdir) $ do
       --liftIO $ print "starting up session"
       dflags <- getSessionDynFlags