It crashes with plain too:
tyluatex: ../../../texk/web2c/luatexdir/pdf/pdfpage.w:97:
synch_pos_with_cur: Assertion `0' failed.
))
(./bidi.lua)
Module luatexbase-mcb info: inserting 'BiDi processing (pre_line)'
(luatexbase-mcb) at position 1 in 'pre_linebreak_filter'
Module luatexbase-mcb info: inserting 'BiDi processing (hpack)'
(luatexbase-mcb) at position 1 in 'hpack_filter'
) [1
Process crashed
\input luadirections
\halign{\hfil \it # & # \hfil \cr
3 cl & cream \cr
2 cl & beer \cr
1.5 cl & orang-utan soup \cr}
\bye
