GHC panic with -O -fno-cpr-anal -fno-cse -fno-full-laziness

Summary

Panic in GHC 9.4.3 when compiling 4-line program with -O -fno-cpr-anal -fno-cse -fno-full-laziness. No panic occurs on 9.2.5.

Steps to reproduce

Put the following code in a file named Bug.hs

module Bug where

import Data.Set

foo x = sequence_ [ f y | y <- x ]
  where f _ = return (fromList [0])

Now, on the command line:

$ ghc -O -fno-cpr-anal -fno-cse -fno-full-laziness Bug.hs
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )

<no location info>: error:
    panic! (the 'impossible' happened)
  GHC version 9.4.3:
	completeCall
  conrep_X1
  Stop[BoringCtxt] Integer
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/GHC/Utils/Panic.hs:182:37 in ghc:GHC.Utils.Panic
        pprPanic, called at compiler/GHC/Core/Opt/Simplify.hs:1911:9 in ghc:GHC.Core.Opt.Simplify

Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug

Removing any of the command-line flags seems to cause the panic to disappear.

Expected behavior

Compile without a panic.

(Why the strange combination of flags? One of our larger source files takes a long time to compile unless cpr-anal is turned off. The other options are there for historic reasons and not really needed, but still I thought I'd report the bug in case in shows up in other ways.)

Environment

• GHC version used: 9.4.3

Optional:

• Operating System: Linux
• System Architecture: x86_64