#14105: ApplicativeDo causes GHC panic on irrefutable list pattern match -------------------------------------+------------------------------------- Reporter: BoteboTsebo | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: ApplicativeDo Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Compile-time | (amd64) crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by lippling): I think this is not fixed completely. With 8.2.2 I get: {{{ [62 of 63] Compiling Handler.Arena ( Handler/Arena.hs, .stack- work/dist/x86_64-osx/Cabal-2.0.1.0/build/Handler/Arena.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-apple-darwin): isStrictPattern Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Disabling ApplicativeDo helps. I don't know what triggers it, yet. If you need to know, I'll try to find a minimal example. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14105#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler