Properly handle holes following spreads in array literals

Properly handle holes following spreads in array literals

Before this change, the spread desugaring would naively call
`%AppendElement($R, the_hole)` and in some cases $R would have
a non-holey elements kind, putting the array into the bad state
of exposing holes to author code.

This patch avoids calling %AppendElement with a hole, instead
simply incrementing $R.length when it sees a hole in the literal
(this is safe because $R is known to be an Array). The existing
logic for elements transitions takes care of giving the array a
holey ElementsKind.

BUG=chromium:644215
Committed: https://crrev.com/e4273007b613950845e92d479485ec737eb61185
Cr-Commit-Position: refs/heads/master@{#39294}

[adamk, 2016-09-07 19:13:19]

The CQ bit was checked by adamk@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-07 19:13:25]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[adamk, 2016-09-07 19:14:16]

adamk@chromium.org changed reviewers:
+ jkummerow@chromium.org, nikolaos@chromium.org

[commit-bot: I haz the power, 2016-09-07 19:44:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-07 19:44:24]

Dry run: This issue passed the CQ dry run.

[nickie, 2016-09-08 08:29:47]

lgtm

[Jakob Kummerow, 2016-09-08 09:58:56]

lgtm

https://codereview.chromium.org/2321533003/diff/20001/src/parsing/parser.cc
File src/parsing/parser.cc (right):

https://codereview.chromium.org/2321533003/diff/20001/src/parsing/parser.cc#n...
src/parsing/parser.cc:5072: auto length_property = factory()->NewProperty(
nit: I strongly prefer explicit types over "auto".

[adamk, 2016-09-08 17:43:20]

https://codereview.chromium.org/2321533003/diff/20001/src/parsing/parser.cc
File src/parsing/parser.cc (right):

https://codereview.chromium.org/2321533003/diff/20001/src/parsing/parser.cc#n...
src/parsing/parser.cc:5072: auto length_property = factory()->NewProperty(
On 2016/09/08 09:58:56, Jakob Kummerow wrote:
> nit: I strongly prefer explicit types over "auto".

Done, but I wish we could have a style guide somewhere for things like this.

[adamk, 2016-09-08 17:43:37]

The CQ bit was checked by adamk@chromium.org

[adamk, 2016-09-08 17:43:38]

The patchset sent to the CQ was uploaded after l-g-t-m from
nikolaos@chromium.org, jkummerow@chromium.org
Link to the patchset: https://codereview.chromium.org/2321533003/#ps40001
(title: "Less auto")

[commit-bot: I haz the power, 2016-09-08 17:43:41]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-08 18:50:21]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-09-08 18:50:48]

Description was changed from

==========
Properly handle holes following spreads in array literals

Before this change, the spread desugaring would naively call
`%AppendElement($R, the_hole)` and in some cases $R would have
a non-holey elements kind, putting the array into the bad state
of exposing holes to author code.

This patch avoids calling %AppendElement with a hole, instead
simply incrementing $R.length when it sees a hole in the literal
(this is safe because $R is known to be an Array). The existing
logic for elements transitions takes care of giving the array a
holey ElementsKind.

BUG=chromium:644215
==========

to

==========
Properly handle holes following spreads in array literals

Before this change, the spread desugaring would naively call
`%AppendElement($R, the_hole)` and in some cases $R would have
a non-holey elements kind, putting the array into the bad state
of exposing holes to author code.

This patch avoids calling %AppendElement with a hole, instead
simply incrementing $R.length when it sees a hole in the literal
(this is safe because $R is known to be an Array). The existing
logic for elements transitions takes care of giving the array a
holey ElementsKind.

BUG=chromium:644215

Committed: https://crrev.com/e4273007b613950845e92d479485ec737eb61185
Cr-Commit-Position: refs/heads/master@{#39294}
==========

[commit-bot: I haz the power, 2016-09-08 18:50:51]

Patchset 3 (id:??) landed as
https://crrev.com/e4273007b613950845e92d479485ec737eb61185
Cr-Commit-Position: refs/heads/master@{#39294}