$ cabal haddock
Configuration is affected by the following files:
- cabal.project
Warning: The package list for 'hackage.haskell.org' is 58 days old.
Run 'cabal update' to get the latest list of available packages.
Resolving dependencies...
Build profile: -w ghc-9.8.4 -O1
In order, the following will be built (use -v for more details):
 - haddock-panic-repro-0.1.0.0 (lib) (first run)
Configuring library for haddock-panic-repro-0.1.0.0...
Preprocessing library for haddock-panic-repro-0.1.0.0...
Running Haddock on library for haddock-panic-repro-0.1.0.0...
[1 of 2] Compiling Inner            ( src/Inner.hs, nothing )
[2 of 2] Compiling Reexport         ( src/Reexport.hs, nothing )
Haddock coverage:
   0% (  0 /  3) in 'Inner'
  Missing documentation for:
    Module header
    Operation (src/Inner.hs:6)
    UpdateableInt (src/Inner.hs:8)
   0% (  0 /  4) in 'Reexport'
  Missing documentation for:
    Module header
    Operation (src/Inner.hs:6)
    Create (src/Inner.hs:6)
    Update (src/Inner.hs:6)
panic! (the 'impossible' happened)
  GHC version 9.8.4:
        tyConStupidTheta

Create
Call stack:
    CallStack (from HasCallStack):
      callStackDoc, called at compiler/GHC/Utils/Panic.hs:191:37 in ghc-9.8.4-inplace:GHC.Utils.Panic
      pprPanic, called at compiler/GHC/Core/TyCon.hs:2606:17 in ghc-9.8.4-inplace:GHC.Core.TyCon

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

Error: [Cabal-7125]
Failed to build documentation for haddock-panic-repro-0.1.0.0.