ES6: Map and Set needs to normalize minus zero

ES6: Map and Set needs to normalize minus zero

BUG=v8:3069
LOG=Y
R=rossberg@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=18892

[Sven Panne, 2014-01-28 07:35:52]

Quick DBC...

https://codereview.chromium.org/147143003/diff/30001/src/collection.js
File src/collection.js (right):

https://codereview.chromium.org/147143003/diff/30001/src/collection.js#newcode51
src/collection.js:51: if (%_IsMinusZero(key)) {
I think using "key === 0" should be more efficient and easier to read. Unless
I'm missing some obscure edge case of course... :-)

[rossberg, 2014-01-28 14:33:18]

LGTM, modulo Sven's comment

[arv (Not doing code reviews), 2014-01-28 18:52:15]

Updated. PTAL

[rossberg, 2014-01-28 21:59:45]

LGTM. Sven, could you please land this? I don't have access to a suitable
machine right now.

[Sven Panne, 2014-01-29 07:27:13]

Committed patchset #2 manually as r18892 (presubmit successful).

[VMuhachev, 2014-01-29 08:29:29]

On 2014/01/29 07:27:13, Sven Panne wrote:
> Committed patchset #2 manually as r18892 (presubmit successful).

But how will this work after somebody will have implemented iteration over keys?

[arv (Not doing code reviews), 2014-01-31 00:14:18]

On 2014/01/29 08:29:29, VMuhachev wrote:
> On 2014/01/29 07:27:13, Sven Panne wrote:
> > Committed patchset #2 manually as r18892 (presubmit successful).
> 
> But how will this work after somebody will have implemented iteration over
keys?

What do you mean? The following is the correct ES6 behavior.

var map = new Map();
map.set(+0, 'plus');
map.set(-0, 'minus');
var keys = [...map.keys()];
assert.equal(keys.length, 1);
assert.equal(1 / keys[0], +Infinity);

We will never store a key with the value -0.