[Maxima] Bug in the itensor package?

[Dmitry Shkirmanov]

Hello,list.

Maxima 5.27.0 http://maxima.sourceforge.net
using Lisp CLISP 2.48 (2009-07-28)
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) load(itensor)$
...
...
(%i2) expr: erfc(-x([i],[])*y([],[i]))$
(%i3) expr: contract(expr)$
(%i4) expr: rename(expr);
(%o4)                   2 - erfc(y([], [i]) x([i], []))
(%i5) diff(expr, y([],[i]));
                   2           2
                - y ([], [i]) x ([i], [])
            2 %e                          x([i], []) kdelta([i], [i])
(%o5)      ---------------------------------------------------------
                                    sqrt(%pi)
(%i6)
As it can be seen from this example, the rename() function does not work correctly. Next, it seems, that the diff() function
does not work correctly too. Is it bug?