Skip to content

GHC panic: Bogus proof for stuck type family. (polysemy-plugin)

Summary

Build fails with panic in polysemy-plugin.

Steps to reproduce

In this code:

https://github.com/kephas/xdg-basedir-compliant/tree/polysemy-bug

Running cabal build triggers this error:

ghc: panic! (the 'impossible' happened)
  (GHC version 9.0.2:
        Bogus proof for stuck type family.

This means there's a type error in your program, but the fact that
you're seeing this message is a bug in `polysemy-plugin`.

Please file a bug at https://github.com/polysemy-research/polysemy
with a minimal reproduction for how you managed to get this error.

CallStack (from HasCallStack):
  error, called at src/Polysemy/Plugin/Fundep.hs:288:9 in polysemy-plugin-0.4.1.1-EpBKoXMm5HlTiTBA0k24:Polysemy.Plugin.Fundep

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

cabal: Failed to build xdg-basedir-compliant-1.0.0 (which is required by
test:xdg-test from xdg-basedir-compliant-1.0.0).

Expected behavior

Build should fail with a type error.

Environment

  • GHC version used: 9.0.2 (from nixpkgs)

Optional:

  • Operating System: Linux
  • System Architecture: amd64
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information