Panic (dsImpSpecs) when specializing non-INLINE function with -O

Summary

<no location info>: error:
    ghc: panic! (the 'impossible' happened)
  (GHC version 8.6.5 for x86_64-unknown-linux):
        dsImpSpecs
  getRandomPrimFromRandomGenState
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable
        pprPanic, called at compiler/deSugar/DsBinds.hs:725:28 in ghc:DsBinds
Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

ghc: panic! (the ‘impossible’ happened)
  (GHC version 8.8.3 for x86_64-apple-darwin):
        dsImpSpecs
  getRandomPrimFromRandomGenState
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1159:37 in ghc:Outputable
        pprPanic, called at compiler/deSugar/DsBinds.hs:730:28 in ghc:DsBinds
Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug

Steps to reproduce

https://github.com/haskell-numerics/random-fu/commit/85af2544728e4b71fbb9c66972a0782a3178b74f

nix-build release.nix

Expected behavior

Not panic.

Environment

• GHC version used: 8.6.5 and 8.8.3

Optional:

• Operating System:
• System Architecture:

See https://circleci.com/gh/haskell-numerics/random-fu/4