[commit: Cabal] : Fix selecting paired packages (a6ca8e6)

[Ian Lynagh]

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

On branch  : 

http://hackage.haskell.org/trac/ghc/changeset/a6ca8e6746037031507eb0c0aee6094c313748e9

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

commit a6ca8e6746037031507eb0c0aee6094c313748e9
Author: Duncan Coutts <duncan at haskell.org>
Date:   Tue Oct 7 06:29:30 2008 +0000

    Fix selecting paired packages
    Previously when we selected base 4 (and as a consequence
    slected base 3 too) we didn't properly trace the dependencies
    of base 3 so if nothing actually required base 3 then we ended
    up with base 3 in the solution but not with syb which it
    depends on. Consequently the solution was invalid.
    Now we select the paired package properly (hopefully).

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

 .../Distribution/Client/Dependency/TopDown.hs      |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/cabal-install/Distribution/Client/Dependency/TopDown.hs b/cabal-install/Distribution/Client/Dependency/TopDown.hs
index dfb0646..9d0ac8b 100644
--- a/cabal-install/Distribution/Client/Dependency/TopDown.hs
+++ b/cabal-install/Distribution/Client/Dependency/TopDown.hs
@@ -170,10 +170,10 @@ searchSpace configure constraints selected changes next =
                     (PackageIndex.lookupPackageId available pkgid')
 
           newPkgs   = [ name'
-                      | dep <- packageConstraints pkg'
+                      | dep <- newDeps
                       , let (Dependency name' _) = untagDependency dep
                       , null (PackageIndex.lookupPackageName selected' name') ]
-          newDeps   = packageConstraints pkg'
+          newDeps   = concatMap packageConstraints newSelected
           next'     = Set.delete name
                     $ foldl' (flip Set.insert) next newPkgs