#14934: Repeated "impossible" go_axiom_rule error. -------------------------------------+------------------------------------- Reporter: galen | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I am getting the following error repeatedly: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.4.1 for x86_64-unknown-linux): go_axiom_rule Sub0R Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler/iface/TcIface.hs:1371:15 in ghc:TcIface }}} I got it on 8.2.1, and tried upgrading to 8.4.1 to see if it went away, but it did not. It occurs frequently when I do a `--make` and recompile a subset of modules. I can avoid it by force-recompiling all modules, although of course this is inefficient. Since I'm working with a codebase of thousands of lines and don't understand ghc's innards, I'm not sure where to start looking for the cause, to produce a minimal failing example. But it did start happening around the time I expanded my use of this module: https://github.com/agrafix/superrecord Since there are unsafe operations in there, it is possible it is doing something illicit, but it is hard to see how it would cause this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14934 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler