[luatex] \U*spacing and pointer

[Manuel Pégourié-Gonnard]

Hi,

Consider the following test file for LuaTeX with Plain:

\newmuskip\testmuskip
\testmuskip=18mu
\thinmuskip=18mu

\Umathopopspacing\textstyle=\testmuskip
\Umathordordspacing\textstyle=\thinmuskip
$11$\par % 18mu, ok
$++$\par % 18mu, ok

\testmuskip=0mu
\thinmuskip=0mu
$11$\par % 0 mu ?!
$++$\par % 0 mu, ok

\bye

I would have expected a different result on the line marked '?!'. Quoting from
the manual:

> Note 1: for ease of use as well as for backward compatibility,
> \thinmuskip, \medmuskip and \thickmuskip are treated especially. In
> their case a pointer to the corresponding internal parameter is
> saved, not the actual \muskip value. This means that any later changes
> to one of these three parameters will be taken into account.

Looks like this special treatment is extended to muskip registers as
well. Is that on purpose or only an unintended side-effect?

Manuel.

PS : This is LuaTeX, Version beta-0.70.0-2011050620 (rev 4250)