Ticket #3431 (closed bug: duplicate)
Loading this module causes panic in interpreter.
This file causes a panic when I try to load it in ghci; but it compiles okay with ghc.
Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> :load Submutations.hs [1 of 1] Compiling Submutations ( Submutations.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 6.10.4 for i386-apple-darwin): schemeE(AnnCase).my_discr __word 0 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug >
This bug has been observed with 6.10.3 on OS X and 6.10.4 on both OS X and x86_64 Linux.
When the definition of permutations is commented out and replaced with undefined, the problem goes away.