Laszlo,
This patch contains a typo, and does not compile for me.
Yes, I sent it off too quickly. I attach a revised version of the patch, that fixes the typo, improves the parser by allowing parentheses in version range expressions, and adds a check that the new syntax is accepted only by cabal >= 1.8.
http://sites.google.com/site/rizsotto/patches/cabal-ticket212.darcs
I have been having great trouble finding a way to test my patch - e.g. darcs cabal-install does not build with darcs Cabal currently. Since you appear to have a testing framework that is not yet incorporated into the standard Cabal repo, I would be very grateful if you could test the revised patch and let me know of any remaining errors.
And I also tried to solve this ticket earlier, here is my solution:
Regards, Malcolm