I'm trying to port Conal Elliott's ConCat plugin from ghc 8 to 9, and the divergence checker foils me. Background: The plugin works by transforming calls to a pseudo-function toCcc' defined like so: -- | Pseudo function to trigger rewriting to TOCCC form. toCcc' :: forall k a b. (a -> b) -> (a `k` b) toCcc' _ = oops "toCcc' called" {-# NOINLINE toCcc' #-} For ghc 8, oops was defined like so: module ConCat.Misc where -- | Pseudo function to fool GHC's divergence checker. oops :: String -> b oops str = errorWithStackTrace ("Oops: "++str) {-# NOINLINE oops #-} ... but unfortunately, ghc 9 is not so easily fooled and reports <A>x for toCcc'. Is there any way to prevent this that works for ghc 9? Help would be much appreciated! -- Regards, Mike