[commit: packages/Cabal] ghc-head: Add a FIXME. (bd25285)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/Cabal

On branch  : ghc-head
Link       : http://git.haskell.org/?p=packages/Cabal.git;a=commit;h=bd25285f313860acca43f00b76f8d31f4aa04bc2

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

commit bd25285f313860acca43f00b76f8d31f4aa04bc2
Author: Mikhail Glushenkov <mikhail.glushenkov at gmail.com>
Date:   Wed Sep 4 00:45:16 2013 +0200

    Add a FIXME.


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

bd25285f313860acca43f00b76f8d31f4aa04bc2
 Cabal/Distribution/Simple/PackageIndex.hs |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/Cabal/Distribution/Simple/PackageIndex.hs b/Cabal/Distribution/Simple/PackageIndex.hs
index edb671f..bcb75eb 100644
--- a/Cabal/Distribution/Simple/PackageIndex.hs
+++ b/Cabal/Distribution/Simple/PackageIndex.hs
@@ -106,6 +106,8 @@ data PackageIndex = PackageIndex
   -- of the same package version. These are unique by InstalledPackageId
   -- and are kept in preference order.
   --
+  -- FIXME: Clarify what "preference order" means. Check that this invariant is
+  -- preserved. See #1463 for discussion.
   !(Map PackageName (Map Version [InstalledPackageInfo]))
 
   deriving (Show, Read)