Mysterious RULES-related(?) panic with 9.2.1
While working on this bytestring pull request, one of my changes caused GHC 9.2.1 to mysteriously panic instead of successfully compiling the Data.ByteString.Internal module, as witnessed by my local testing and this CI run.
Steps to reproduce
Compiling this file Internal.hs with GHC 9.2.1 produces the following error message:
Click to expand
ghc: panic! (the 'impossible' happened)
(GHC version 9.2.1:
refineFromInScope
InScope {wild_00 $dIP_a16J $cp1Monoid_a16N $cmempty_a16P
$cmappend_a16X $cmconcat_a174 $c<>_a17c $csconcat_a17j $krep_a18N
concat stimesPolymorphic stimesInt $tc'BS $tcByteString
$fMonoidByteString $fSemigroupByteString $trModule $dIP_s19g}
$dMonoid_a15E
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/GHC/Utils/Panic.hs:181:37 in ghc:GHC.Utils.Panic
pprPanic, called at compiler/GHC/Core/Opt/Simplify/Env.hs:706:30 in ghc:GHC.Core.Opt.Simplify.Env
Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug
Environment
- GHC version used: 9.2.1
- Operating System: WSL v2 on Windows 10
- System Architecture: x86-64