compiler option -XDoRec crash

I tried to compile a complex 200 KByte grammer using the library frisby. I got a linking error. The file is essentially one big "do rec" block and thus needs -XDoRec compiler option. I installed the latest GHC Version and use the minus -C flag to analyze the problem, which resulted in a ghc panic.

dirk@dirk-desktop:~/temp/wb2pdf/trunk/exp$ ghc  -C  -XDoRec Grammer.hs
addFlag by -C on the commandline:
    Warning: The -fvia-C flag does nothing; it will be removed in a future GHC release
ghc: panic! (the 'impossible' happened)
  (GHC version 7.2.2 for i386-unknown-linux):
	pipeLoop: at phase As but I wanted to stop at phase HCc

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

Edited Mar 09, 2019 by Ian Lynagh <igloo@earth.li>

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information