X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FDesugar.hs;h=eaa15dcf3e7f0db2d9d96f8e76415e406bc033cc;hb=81b217b104feb963e00537a51e6b3dfee8163b86;hp=67ff6638f4674bd6697bee056151bfed5a6467ef;hpb=5b2b5621f83723e22beb4b6cbbf5963ee34d548b;p=ghc-base.git

diff --git a/GHC/Desugar.hs b/GHC/Desugar.hs
index 67ff663..eaa15dc 100644
--- a/GHC/Desugar.hs
+++ b/GHC/Desugar.hs
@@ -13,11 +13,11 @@
 -----------------------------------------------------------------------------
 
 -- #hide
-module GHC.Desugar ((>>>)) where
+module GHC.Desugar ((>>>), AnnotationWrapper(..), toAnnotationWrapper) where
 
 import Control.Arrow    (Arrow(..))
 import Control.Category ((.))
-import Prelude hiding ((.))
+import Data.Data        (Data)
 
 -- A version of Control.Category.>>> overloaded on Arrow
 #ifndef __HADDOCK__
@@ -28,3 +28,9 @@ import Prelude hiding ((.))
 --     Yes, this is a bit grotesque, but heck it works and the whole
 --     arrows stuff needs reworking anyway!
 f >>> g = g . f
+
+-- A wrapper data type that lets the typechecker get at the appropriate dictionaries for an annotation
+data AnnotationWrapper = forall a. (Data a) => AnnotationWrapper a
+
+toAnnotationWrapper :: (Data a) => a -> AnnotationWrapper
+toAnnotationWrapper what = AnnotationWrapper what