Subj : trouble with combination of "for/in" and "with" block
To   : netscape.public.mozilla.jseng
From : archer
Date : Fri Jul 23 2004 07:32 pm

To moderator: this is a copy/follow-up to an earlier message which
went out on error. Please kill first one if possible.

Hi,
I use JSRef 1.5r6a and encounter the following problem:
an object from outer scope ("i" in the example below) is being
modified by a "for...in" iteration when it is placed inside a "with"
block.

Older JSRef (1.4?) used to run the same code without the problem, and
so does WScript/CScript.
Also, there is NO problem if ANY one of conditions listed below is
true:
A. if "with" block is absent
B. if "for( ; ; )" is used instead of "for...in"
C. if object with same name as object in question appears somewhere
else in the inner scope (of function "f()")

I believe it is a bug, right? I did not find a test case in
ftp://ftp.mozilla.org/pub/mozilla.org/js/js-tests-20021118.tar.gz
that covers my set of conditions.

I understand my case is very specific, and I totally agree that "with"
statement is a poor practice to begin with. But this case that I have
is present in an old code that I have running at a customer site. :(

Is it possible to use some settings/switches to re-compile the JSRef
to remedy this? Or does it have to be a fix? Please help if possible.

<code>
var unrelated_object = {};
var i = 4444;

function f()
{
with ( unrelated_object )       //// A. comment out to eliminate
problem
  for ( var i in [7,7,7] ) {}
//  for ( var i = 333; 0; ) {}  //// B. this flavor of "for" has no
problem
//var i = "lalala";           //// C. un-comment it to eliminate
problem
}

f();

print( ''+ i );  // prints "2", whereas expected "4444"
</code>

Thanks!

Aleksey Chernoraenko,
MetaCommunications Engineering.

.