[luatex] 'Out by one' error (?) in \csname messages

[Akira Kakuto]

With the TL2014 pretest version of LuaTeX,

    \csname\csname\endcsname
leads to the error

    ! Missing \endcsname inserted.
    <to be read again>
    \^^@csnam\^^@endcsnam
    l.1 \csname\csname\endcsname

which looks like some form of 'out by one' issue.

I think that is related to the following, since
it is already fixed in the LuaTeX trunk.

%
% s.tex
%
\def\use#1{#1}
\use\fXabc
\bye

(./s.tex
! Undefined control sequence.
<argument> \fXabc 
      
\use #1X-#1
          
l.2 \use\fXabc

Best,
Akira