runTestTT from ghci caused a panic.
Inside a REPL within Emacs+Intero-mode, running a stack project. I am writing a simple lexer for fun and I decided to try to see why I wasn't getting expected behaviour from an HUnit function.
I have attached the tar-balled stack project for completeness, apologies for the size but I didn't want to risk omiotting anything important to you guys if this ever gets looked at in the melee!
runTestTT classificationTests ghc: panic! (the 'impossible' happened) (GHC version 8.4.4 for x86_64-unknown-linux): nameModule system $dShow_a5Xw Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler/basicTypes/Name.hs:241:3 in ghc:Name