281930 - |this| is set to wrong value inside function expression

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect, P3)

Description

[Erik Fabert]

After executing the following line,

var rv = function() { return this; }();

rv should be a reference to the global object. It is a reference to the
anonymous function instead.

Comment 1

[Erik Fabert]

Attachment: testcase as described above

Expected output:
true
[object Window]

Actual output:
false
function () { return this; }

Comment 2

[Bob Clary [:bc] (inactive)]

Attachment: corrected test case

you are testing a reference to the function against windows and not the return
value of calling the function. INVALID.

Comment 3

[Erik Fabert]

Please look at my testcase again: I'm calling the function but I don't get the
expected return value. This works as I expect in IE6, Opera, Netscape 4.75 and
Rhino.

Comment 4

[Bob Clary [:bc] (inactive)]

Attachment: second attempt at testcase

Sorry, I missed the trailing () call on the function expression. 

var rv = function() { return this; }(); 

sets rv to the function rather than the result of calling the expression. 

var rv = (function() { return this; })(); 

will work. The bug isn't about |this| being wrong but is about the () call
being ignored.

Comment 5

[Erik Fabert]

Sorry, but that's not right either. If you modify the line to 

var rv = function() { alert("Yo"); return this; }();

you'll see the function gets called properly.

Comment 6

[Bob Clary [:bc] (inactive)]

you are right. If you change the alert("Yo") to alert(this) you see that |this|
is the function expression. 

Comment 7

[Brendan Eich [:brendan]]

Attachment: fix

I'm going to check this in when the trunk opens; shaver, feel free to stamp r=
any time.

/be

Comment 8

[Mike Shaver (:shaver emeritus)]

Comment on attachment 174076 [details] [diff] [review]
fix

r=shaver

Comment 9

[Boris Zbarsky [:bzbarsky]]

Trunk's open...

Comment 10

[Brendan Eich [:brendan]]

So it is, thanks for the nudge.

/be

Comment 11

[Erik Fabert]

Verified with build 20050223, thanks!

Comment 12

[Bob Clary [:bc] (inactive)]

js/tests/js1_5/Regress/regress-281930.js checked in with Erik's permission.