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

Trac metadata

Trac field	Value
Version	8.4.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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