Redefine appendFS in terms of appendFB

I think the old definition had a bug, although it probably never
actually bit us: It used lengthFS to work out how large the arguments
where, but lengthFS returns the number of characters, not bytes.

1 files changed, 4 insertions, 12 deletions

diff --git a/compiler/utils/FastString.lhs b/compiler/utils/FastString.lhs
index a340e6eedb..29965b188f 100644
--- a/compiler/utils/FastString.lhs
+++ b/compiler/utils/FastString.lhs
@@ -540,18 +540,10 @@ zEncodeFS fs@(FastString _ _ _ _ enc) =
             return efs
 
 appendFS :: FastString -> FastString -> FastString
-appendFS fs1 fs2 =
-  inlinePerformIO $ do
-    r <- mallocForeignPtrBytes len
-    withForeignPtr r $ \ r' -> do
-    withForeignPtr (buf fs1) $ \ fs1Ptr -> do
-    withForeignPtr (buf fs2) $ \ fs2Ptr -> do
-        copyBytes r' fs1Ptr len1
-        copyBytes (advancePtr r' len1) fs2Ptr len2
-        mkFastStringForeignPtr r' r len
-  where len  = len1 + len2
-        len1 = lengthFS fs1
-        len2 = lengthFS fs2
+appendFS fs1 fs2 = inlinePerformIO
+                 $ mkFastStringFastBytes
+                 $ appendFB (fastStringToFastBytes fs1)
+                            (fastStringToFastBytes fs2)
 
 concatFS :: [FastString] -> FastString
 concatFS ls = mkFastString (Prelude.concat (map unpackFS ls)) -- ToDo: do better