[commit: Cabal] master: Fix a case in the new solver pruning pass (8068632)

[Ian Lynagh]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/80686328e520564839a723ad1ac91e79a032d874

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

commit 80686328e520564839a723ad1ac91e79a032d874
Author: Duncan Coutts <duncan at haskell.org>
Date:   Mon Apr 18 21:12:11 2011 +0000

    Fix a case in the new solver pruning pass
    It is actually possible for pruning to eliminate required packages
    because it's possible for it to propagate all the way up to one of
    the initial targets.

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

 .../Distribution/Client/Dependency/TopDown.hs      |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/cabal-install/Distribution/Client/Dependency/TopDown.hs b/cabal-install/Distribution/Client/Dependency/TopDown.hs
index 8b1bb64..cd36b53 100644
--- a/cabal-install/Distribution/Client/Dependency/TopDown.hs
+++ b/cabal-install/Distribution/Client/Dependency/TopDown.hs
@@ -354,8 +354,7 @@ pruneBottomUp platform comp constraints =
         Satisfiable cs' [pkgid]| packageId pkg == pkgid
                          -> Step (ExcludeUnconfigurable pkgid) (rest cs')
         Satisfiable _ _  -> impossible
-        Unsatisfiable    -> impossible
-        ConflictsWith _  -> Fail $ ConfigureFailed pkg
+        _                -> Fail $ ConfigureFailed pkg
                               [ (dep, Constraints.conflicting cs dep)
                               | dep <- missing ]