155748 - Can't use a global variable named "parent"

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Pedro Lopes]

If a global variable is declared with the name "parent" - (the same as a builtin
variable), any attempt to refer to it will intead refer to the original
(builtin) variable. 
This only happens with "parent". As far as I can tell, using other builtin
variable's names works correctly.

For example (this is from the attached testcase):

// this works as expected
var top;
top = "this is a variable named top";
alert(top);

// this fails in the assignment with "Error: setting a property that has only a
getter"
var parent;
parent = "this is a variable named parent";
alert(parent);

Comment 1

[Pedro Lopes]

Attachment: simple testcase

Comment 2

[José Jeria]

parent and top are reserverd Javascript keywords. Reserved words have a 
specific meaning to the Javascript language.

Using a reserved word causes a compilation error.

This should be marked as INVALID.

Comment 3

[Pedro Lopes]

No, no, that's completely wrong! :)
When you declare a variable, it should "hide" a variable of the same name that
was previously in scope.
Run the test case in NS4 or IE to see the correct behaviour. Mozilla also does
it right most of the time, it's just "parent" that fails for some reason.

Comment 4

[David G King]

If "parent" is a reserved word, then why couldn't I find it in the ECMAScript
Language Specification Edition 3 (equiv to JS 1.5). See
http://www.mozilla.org/js/language/ for more details.

Comment 5

[Alex Vincent [:WeirdAl]]

This bug might actually apply to "top" instead of "parent".  The inconsistent
behavior is almost certainly a bug.

It's certainly not a JSENG bug, because "top" and "parent" refer to windows. 
ECMAScript doesn't cover windows at all.

Comment 6

[Alex Vincent [:WeirdAl]]

.

Comment 7

[Mike Young]

parent is not reserved, and is not included in Netscape's JS/DOM 0 Reference
(for v1.3) at http://developer.netscape.com/docs/manuals/js/client/jsref/index.htm. 

Both the top and parent property of a window are read only, but comment #3 is
correct in that a more local variable should override a more global variable. 

Comment 8

[Christopher Aillon (sabbatical, not receiving bugmail)]

I have a fix

Comment 9

[Christopher Aillon (sabbatical, not receiving bugmail)]

Attachment: Proposed patch v.1.0

I bet this patch probably has some fuzz in it from other unrelated changes to
the same file (I manually removed those hunks) but is otherwise good for
reviewing.

Comment 10

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 90275 [details] [diff] [review]
Proposed patch v.1.0

r=bzbarsky

Comment 11

[Johnny Stenback (:jst)]

Comment on attachment 90275 [details] [diff] [review]
Proposed patch v.1.0

sr=jst

Comment 12

[Christopher Aillon (sabbatical, not receiving bugmail)]

Checked in

Comment 13

[Pedro Lopes]

It's working on build 2002070813

Comment 14

[Christopher Aillon (sabbatical, not receiving bugmail)]

Re-opening, just to get approval1.4b.  This fix was checked in and working for
about a month, but got inadvertently backed out on 2002-08-15.  See bug 159236
comment 9 and later.

Comment 15

[Asa Dotzler [:asa]]

Comment on attachment 90275 [details] [diff] [review]
Proposed patch v.1.0

a=asa (on behalf of drivers) for checkin to 1.4b

Comment 16

[Christopher Aillon (sabbatical, not receiving bugmail)]

Checked in again.  Let's hope it stays there this time :-)