Tidy up the treatment of newtypes, refactor, and fix Trac #736

[ghc-hetmet.git] / compiler / basicTypes / DataCon.lhs

diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs
index 9ce966e..dbc6355 100644 (file)
--- a/compiler/basicTypes/DataCon.lhs
+++ b/compiler/basicTypes/DataCon.lhs
@@ -766,8 +766,9 @@ splitProductType str ty
 deepSplitProductType_maybe ty
   = do { (res@(tycon, tycon_args, _, _)) <- splitProductType_maybe ty
        ; let {result 
-             | isClosedNewTyCon tycon && not (isRecursiveTyCon tycon)
-             = deepSplitProductType_maybe (newTyConInstRhs tycon tycon_args)
+             | Just (ty', _co) <- instNewTyCon_maybe tycon tycon_args
+            , not (isRecursiveTyCon tycon)
+             = deepSplitProductType_maybe ty'  -- Ignore the coercion?
              | isNewTyCon tycon = Nothing  -- cannot unbox through recursive
                                           -- newtypes nor through families
              | otherwise = Just res}