Compiler panic: genApp: invalid size when using UnliftedNewtypes

[amesgen]

The minimal example

{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE UnliftedNewtypes #-}

newtype Foo = Foo (# #)

fails to compile:

panic! (the 'impossible' happened)
  (GHCJS version 8.10.7, GHC version 8.10.7):
        genApp: invalid size

Please report this as a GHCJS bug:  https://github.com/ghcjs/ghcjs/issues

Context

I encountered this in GHC.Parser.Lexer in GHC 9.4, where ParseResult is an unlifted newtype: https://gitlab.haskell.org/ghc/ghc/-/blob/ghc-9.4.1-rc1/compiler/GHC/Parser/Lexer.x#L2328

Note that type synonyms for unlifted types work just fine:

type Foo = (# #)

Minimal reproducible example

https://github.com/amesgen/stuff/tree/ghcjs-unlifted

nix build github:amesgen/stuff/ghcjs-unlifted