I've got the answer at #ghc irc channel. With resultIsLevPoly it is possible to filter out the problematic types. Regards, Csaba On Fri, Nov 30, 2018 at 11:08 PM Csaba Hruska wrote:

Is this problem related to the following?

...

{- Note [Error and friends have an "open-tyvar" forall] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 'error' and 'undefined' have types error :: forall (v :: RuntimeRep) (a :: TYPE v). String -> a undefined :: forall (v :: RuntimeRep) (a :: TYPE v). a Notice the runtime-representation polymorphism. This ensures that "error" can be instantiated at unboxed as well as boxed types. This is OK because it never returns, so the return type is irrelevant.

On Fri, Nov 30, 2018 at 10:47 PM Csaba Hruska wrote:

...

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