I tried to reproduce this on GHC 8.2.1, but it builds cleanly, both with `__impossible` and `undefined`. I'm using the current `master` branch
#14777: panic when using a function defined in terms of `error` -------------------------------------+------------------------------------- Reporter: zilinc | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by zilinc): Replying to [comment:11 tdammers]: though, because the specified commit doesn't seem to exist in any of the exposed branches anymore. The commit is still there. But I totally believe that you could not reproduce it on an arbitrary commit, otherwise it would be easier to figure out what crashed the compiler. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14777#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler