ghc: panic! (the 'impossible' happened)

(GHC version 7.4.1 for x86_64-unknown-linux):

nameModule b_a2PR{tv}

While working on this project https://github.com/mightybyte/snaplet-postgresql-simple I encountered a GHC panic. To reproduce, check out revision 6573d4359c5cb7699c931c44ebf1bf135099f83b (currently HEAD of the master branch), cabal install it, then go to the example directory and build with "ghc --make Site.hs".

This has caused the crash for me on two different Linux systems with GHC 7.4.1. I realize it requires building a large number of package dependencies, but I have no idea of how to construct a smaller test case. It should be pretty easy to build these dependencies with cabal or cabal-dev.