Add type signatures to cope with lack of local generalisation

[ghc-base.git] / System / IO / Error.hs

diff --git a/System/IO/Error.hs b/System/IO/Error.hs
index 6dcf24d..d1c4e47 100644 (file)
--- a/System/IO/Error.hs
+++ b/System/IO/Error.hs
@@ -419,6 +419,7 @@ annotateIOError ioe loc hdl path =
   ioe{ ioe_handle = hdl `mplus` ioe_handle ioe,
        ioe_location = loc, ioe_filename = path `mplus` ioe_filename ioe }
   where
+    mplus :: Maybe a -> Maybe a -> Maybe a
     Nothing `mplus` ys = ys
     xs      `mplus` _  = xs
 #endif /* __GLASGOW_HASKELL__ || __HUGS__ */