Panic with self-import

A test in the singletons package leads to a panic when run:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.2 for x86_64-unknown-linux):
        tcIfaceGlobal (local): not found:
    singletons-1.0:Singletons.Star.TFCo:R:DemoteRep*KProxy{tc r0}
    []

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Edit: see ticket:9032#comment:83149 for a testcase.