From Fedora Project Wiki

Packages Needing Bootstrap

Most packages in Fedora Extras should be rebuilt between Fedora Core revisions. This helps us avoid having packages that are linked against old versions of libraries and fail to compile with the current versions of the tools provided by Fedora Core.

There are a few packages for which this is not true. These are compilers that are written in the programming language they implement. It could also include circular chains of build tools that are required in order to build themselves. This page is intended to list the packages in Fedora Extras that must be copied from the previous version's repository to the new one in order to break these dependencies and allow us to bootstrap ourselves to packages built only from the current repository plus The equivalent version of Fedora Core.

ghc - The Glasgow Haskell Compiler