Issue with package "pretty"

[David MacIver]

#haskell have just helped me figure out an entertaining issue with the
pretty library on hackage. I couldn't figure out the right place to
file a bug report and the maintainer is listed as
libraries at haskell.org so I'm emailing the list in the hopes that
someone will know what to do about it. :-)

The problem is that if you install pretty, Cabal will suddenly cease
working until you recompile it. It depends on a version of pretty
which gets bundled with GHC is purportedly of the same version as the
one on hackage, but the two aren't binary compatible. So when it tries
to use it, everything goes boom.