GHC panic: MkExternalCore died: make_lit
Compiling the attached example with -fext-core crashes ghc with the following text:
$ ghc -fext-core min.hs [1 of 1] Compiling Main ( min.hs, min.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.4.1 for x86_64-unknown-linux): MkExternalCore died: make_lit
Replacing the data declaration with a newtype or a library type such as
Ratio gives the same crash. An empty
.hcr file is created.
Replacing the "main" action with "return ()" or removing one of the type synonym declarations makes the crash go away.
This is using the ghc package distributed with ubuntu 12.04.