This is LuaTeX, Version beta-0.71.0-2012052701 (rev 4356)  (format=luatex 2012.5.27)  5 AUG 2012 20:28
 restricted \write18 enabled.
**bug.tex
(./bug.tex
{vertical mode: \tracingstats}
{\tracingpages}
{\tracingoutput}
{\tracinglostchars}
{\tracingmacros}
{\tracingparagraphs}
{\tracingrestores}
{\showboxbreadth}
{\showboxdepth}
{\errorstopmode}

{\tracinggroups}
{\tracingifs}
{\tracingscantokens}
{\tracingnesting}
{\tracingassigns}
{into \tracingassigns=2}
{\def}
{changing \A=undefined}
{into \A=macro:->1}
{blank space  }
{\directlua}
{end-group character }}
! Undefined control sequence.
l.6 }
     
? x


Here is how much of LuaTeX's memory you used:
 7 strings out of 496556
 100000,35830 words of node,token memory allocated 167 words of node memory still in use:
   2 hlist, 1 rule, 1 glyph, 18 glue_spec, 1 dir nodes
   avail lists: 2:4,3:1,6:2
 2007 multiletter control sequences out of 65536+200000
 50 fonts using 2034573 bytes
 1i,0n,0p,38b,6s stack positions out of 5000i,500n,10000p,200000b,50000s
No pages of output.

PDF statistics: 0 PDF objects out of 1000 (max. 8388607)
 0 named destinations out of 1000 (max. 131072)
 1 words of extra memory for PDF output out of 10000 (max. 10000000)