[commit: Win32] master: Fix build (f9728fa)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/Win32

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/f9728fa23706eaaeec63b81a604ce957826a83e9

>---------------------------------------------------------------

commit f9728fa23706eaaeec63b81a604ce957826a83e9
Author: Ian Lynagh <igloo at earth.li>
Date:   Fri Oct 14 19:12:23 2011 +0100

    Fix build

>---------------------------------------------------------------

 System/Win32/Types.hs |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/System/Win32/Types.hs b/System/Win32/Types.hs
index 741e36d..816490b 100644
--- a/System/Win32/Types.hs
+++ b/System/Win32/Types.hs
@@ -97,7 +97,7 @@ ptrToMaybe p = if p == nullPtr then Nothing else Just p
 maybeNum :: Num a => Maybe a -> a
 maybeNum = fromMaybe 0
 
-numToMaybe :: Num a => a -> Maybe a
+numToMaybe :: (Eq a, Num a) => a -> Maybe a
 numToMaybe n = if n == 0 then Nothing else Just n
 
 type MbLPVOID      = Maybe LPVOID
@@ -183,7 +183,7 @@ failIf_ p wh act = do
 failIfNull :: String -> IO (Ptr a) -> IO (Ptr a)
 failIfNull = failIf (== nullPtr)
 
-failIfZero :: Num a => String -> IO a -> IO a
+failIfZero :: (Eq a, Num a) => String -> IO a -> IO a
 failIfZero = failIf (== 0)
 
 failIfFalse_ :: String -> IO Bool -> IO ()