Hi, I'd like to export the PrimRep of every binder and data con from Haskell modules. I have a modified GHC 8.6 which serializes the PrimRep for every binder during the compilation. It uses the *typePrimRep* function. When my customised GHC compiles the base library it always thows the following error for the *libraries/base/GHC/Err.hs* https://github.com/grin-tech/ghc-grin/blob/master/ghc-8.6.2/libraries/base/G... module. 1. Does that mean that there is hidden requirement for typePrimRep input? 2. If so what are the restrictions? 3. Can you see anything in the Err module source code that could not be a proper input for typePrimRep function? Thanks, Csaba "inplace/bin/ghc-stage1" -hisuf hi -osuf o -hcsuf hc -static -H32m -O -Wall -this-unit-id base-4.12.0.0 -hide-all-packages -i -ilibraries/base/. -ilibraries/base/dist-install/build -Ilibraries/base/dist-install/build -ilibraries/base/dist-install/build/./autogen -Ilibraries/base/dist-install/build/./autogen -Ilibraries/base/include -Ilibraries/base/dist-install/build/include -optP-DOPTIMISE_INTEGER_GCD_LCM -optP-include -optPlibraries/base/dist-install/build/./autogen/cabal_macros.h -package-id ghc-prim-0.5.3 -package-id integer-gmp-1.0.2.0 -package-id rts -this-unit-id base -Wcompat -Wnoncanonical-monad-instances -XHaskell2010 -O2 -haddock -no-user-package-db -rtsopts -Wno-trustworthy-safe -Wno-deprecated-flags -Wnoncanonical-monad-instances -odir libraries/base/dist-install/build -hidir libraries/base/dist-install/build -stubdir libraries/base/dist-install/build -split-sections -dynamic-too -c libraries/base/./GHC/Err.hs -o libraries/base/dist-install/build/GHC/Err.o -dyno libraries/base/dist-install/build/GHC/Err.dyn_o ghc-stage1: panic! (the 'impossible' happened) (GHC version 8.6.2 for x86_64-unknown-linux): runtimeRepPrimRep typePrimRep (a_a1ML :: TYPE r_a1MK) r_a1MK Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/simplStg/RepType.hs:358:5 in ghc:RepType Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug libraries/base/ghc.mk:4: recipe for target 'libraries/base/dist-install/build/GHC/Err.o' failed make[1]: *** [libraries/base/dist-install/build/GHC/Err.o] Error 1 Makefile:122: recipe for target 'all' failed make: *** [all] Error 2