CoreToStg Assert Failure with -g3

Summary

Running ./hadrian/build -c -j --flavour=validate '*.*.ghc.*.opts += -g3' results in

ghc: panic! (the 'impossible' happened)
  (GHC version 8.11.0.20200615:
	ASSERT failed! file compiler/GHC/CoreToStg.hs, line 933

Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug

Environment

GHC version used: ghc.nix

Optional:

Operating System: Fedora 30
System Architecture: x86-64

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