Combination of unboxed sums and unsafeCoerce# causes compiler panics

If you compile this nonsensical program:

{-# LANGUAGE UnboxedSums, UnboxedTuples, MagicHash #-}

import Unsafe.Coerce
import GHC.Prim

main = do
  let x = (# 1 | #) :: (# Int | Int# #)
  let y = unsafeCoerce# x :: (# (# Int, Int #) | Int# #)

  case y of
    (# (# i1, i2 #) | #) -> do print i1; print i2
    (# | i #) -> return ()

GHC HEAD current panics in GHC.Cmm.Liveness:

{-# LANGUAGE UnboxedSums, UnboxedTuples, MagicHash #-}

import Unsafe.Coerce
import GHC.Prim

main = do
  let x = (# 1 | #) :: (# Int | Int# #)
  let y = unsafeCoerce# x :: (# (# Int, Int #) | Int# #)

  case y of
    (# (# i1, i2 #) | #) -> do print i1; print i2
    (# | i #) -> return ()

While this program doesn't make any sense, I'm not sure if GHC should panic this way (instead of with rejecting the program with a friendly error message) when provided a nonsensical program.

I think it's also possible that this is an actual bug in the code generator.