[luatex] Luatex 1.15.0: bug with letterspacing in Harf mode

[marc]

I noticed a weird bug when using letterspacing in Harf mode in Luatex 
1.15.0 (the TL2022 release); this is not present in 1.13.2 from TL2021. 
A minimal example:


\documentclass{article}

\font\base       = lmroman10-regular:mode=base,letterspace=100.0

\font\node       = lmroman10-regular:mode=node,letterspace=100.0

\font\harf       = lmroman10-regular:mode=harf,letterspace=100.0

\font\harfnokern = lmroman10-regular:mode=harf,letterspace=100.0,-kern

\begin{document}

{\base       CRITIQUE \quad RITIQ}\par

{\node       CRITIQUE \quad RITIQ}\par

{\harf       CRITIQUE \quad RITIQ}\par

{\harfnokern CRITIQUE \quad RITIQ}\par

\end{document}


The third RITIQ isn't letterspaced, while everything else is. Note that 
RITIQ is the shortest string that shows this behaviour (at least with 
this font); shorter substrings do get letterspaced correctly. Curiously 
the word CRITIQUE also typesets fine, even though it contains RITIQ as a 
substring. Finally, letterspacing also works when kerning is disabled, 
even though as far as I can tell none of the letter pairs in RITIQ is 
actually kerned in this font.

The bug is not a big deal for me (noticed it when playing with a new 
font), so please don't waste lots of time on it.


Marc