I just finished tracking down the source of the following error from GHCi: ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): Bytecode generator can't handle unboxed tuples. Possibly due to foreign import/export decls in source. Workaround: compile this module to a .o file, then restart session. Some clue to the source of the problem would be quite helpful. (I expect just about anything to at least be sometime useful -- even if it's the low-level input to bytecode generator.) It turns out the source of the problem is a definition in an imported .hi file. Would it be possible for GHCi to prune the inlined definitions containing unboxed tuples and use the non-inlined ones? (Are the non-inline definitions are in the object file? "nm" suggests they are.) The best fix, of course, would be to make the bytecode generator handle unboxed tuples. thanks, mike