Alberto,

> I've manage to reproduce the CK bug without any external dependencies and

> opened a ticket with an attached module that fails to compile with

> 8.2.1-rc2 (w/o explicit KindSignature) but compiles fine with 8.0.2.

Thanks for doing this!

> Will hopefully follow up soon with the Cabal issues I'm experiencing

One thing that might be useful to do is to invoke Cabal with high verbosity (e.g., -v3) and post the logs somewhere. I wouldn't be surprised if Nix was passing some uncommonly used flags that have regressed in recent versions of Cabal.

Ryan S.