[commit: Cabal] master: fix package ordering bug (52a3294)

[Ian Lynagh]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/52a32946fb286d83b514e1999b6ade30f85ed688

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

commit 52a32946fb286d83b514e1999b6ade30f85ed688
Author: Andres Loeh <andres at well-typed.com>
Date:   Wed Jun 15 07:36:30 2011 +0000

    fix package ordering bug

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

 .../Client/Dependency/Modular/Preference.hs        |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/cabal-install/Distribution/Client/Dependency/Modular/Preference.hs b/cabal-install/Distribution/Client/Dependency/Modular/Preference.hs
index a03a189..6e46452 100644
--- a/cabal-install/Distribution/Client/Dependency/Modular/Preference.hs
+++ b/cabal-install/Distribution/Client/Dependency/Modular/Preference.hs
@@ -51,8 +51,13 @@ preferPackagePreferences pcs = packageOrderFor (const True) preference
       in  preferredVersionsOrdering vr v1 v2 `mappend` -- combines lexically
           locationsOrdering ipref i1 i2
 
-    locationsOrdering PreferInstalled = preferInstalledOrdering
-    locationsOrdering PreferLatest    = preferLatestOrdering
+    -- Note that we always rank installed before uninstalled, and later
+    -- versions before earlier, but we can change the priority of the
+    -- two orderings.
+    locationsOrdering PreferInstalled v1 v2 =
+      preferInstalledOrdering v1 v2 `mappend` preferLatestOrdering v1 v2
+    locationsOrdering PreferLatest v1 v2 =
+      preferLatestOrdering v1 v2 `mappend` preferInstalledOrdering v1 v2
 
 -- | Ordering that treats installed instances as greater than uninstalled ones.
 preferInstalledOrdering :: I -> I -> Ordering