> ~/head.hackage/ghc/bin/ghc Class.hs -O<no location info>: error: panic! (the 'impossible' happened) GHC version 9.6.0.20230220: ASSERT failed! Coercion = Kind (Sym (N:NFData[0] <a_aMw>_N)) LHS ty = * RHS ty = Constraint cs = Tc(0) coercion role = nominal Call stack: CallStack (from HasCallStack): assertPpr, called at compiler/GHC/Core/Coercion.hs:1126:5 in ghc:GHC.Core.Coercion mkSelCo_maybe, called at compiler/GHC/Core/Coercion.hs:1118:16 in ghc:GHC.Core.Coercion mkSelCo, called at compiler/GHC/Core/Coercion.hs:620:5 in ghc:GHC.Core.Coercion mkRuntimeRepCo, called at compiler/GHC/Core/Unify.hs:1584:16 in ghc:GHC.Core.Unify CallStack (from HasCallStack): panic, called at compiler/GHC/Utils/Error.hs:454:29 in ghc:GHC.Utils.ErrorPlease report this as a GHC bug: https://www.haskell.org/ghc/reportabug