Set -fdefer-types-holes in case split

Language/Haskell/GhcMod/CaseSplit.hs

@@ -47,7 +47,7 @@ splits :: IOish m
        -> Int          -- ^ Column number.
        -> GhcModT m String
 splits file lineNo colNo =
-  ghandle handler $ runGmlT' [Left file] deferErrors $ do
+  ghandle handler $ runGmlT' [Left file] deferErrorsAndHoles $ do
       opt <- options
       crdl <- cradle
       style <- getStyle

Language/Haskell/GhcMod/DynFlags.hs

@@ -100,3 +100,7 @@ setNoMaxRelevantBindings = id
 deferErrors :: DynFlags -> Ghc DynFlags
 deferErrors df = return $
   Gap.setWarnTypedHoles $ Gap.setDeferTypeErrors $ setNoWarningFlags df
+
+deferErrorsAndHoles :: DynFlags -> Ghc DynFlags
+deferErrorsAndHoles df = return $
+  Gap.setDeferTypeErrors $ Gap.setDeferTypedHoles $ setNoWarningFlags df

Language/Haskell/GhcMod/Gap.hs

@@ -14,6 +14,7 @@ module Language.Haskell.GhcMod.Gap (
   , setCabalPkg
   , setHideAllPackages
   , setDeferTypeErrors
+  , setDeferTypedHoles
   , setWarnTypedHoles
   , setDumpSplices
   , isDumpSplices
@@ -294,6 +295,13 @@ setDeferTypeErrors dflag = dopt_set dflag Opt_DeferTypeErrors
 setDeferTypeErrors = id
 #endif
 
+setDeferTypedHoles :: DynFlags -> DynFlags
+#if __GLASGOW_HASKELL__ >= 708
+setDeferTypedHoles dflag = gopt_set dflag Opt_DeferTypedHoles
+#else
+setDeferTypedHoles = id
+#endif
+
 setWarnTypedHoles :: DynFlags -> DynFlags
 #if __GLASGOW_HASKELL__ >= 708
 setWarnTypedHoles dflag = wopt_set dflag Opt_WarnTypedHoles