[es6] Fix bug in pattern re-writing

[es6] Fix bug in pattern re-writing

As originally implemented, a SingleNameBinding within a BindingPattern
was incorrectly interpreted as an assignment if an initializer was
present and that initializer was itself an AssignmentExpresion.
For example:

    let x;
    { let [x = y = 1] = []; }
    print(x); // expected: undefined, actual: 1

Extend the heuristic that detects the "context" of a destructuring
pattern to account for AssignmentExpressions within SingleNameBindings.

BUG=v8:4891
LOG=N
R=adamk@chromium.org

Committed: https://crrev.com/9acbca18456c6d4b704f0e98004d2c78795602fe
Cr-Commit-Position: refs/heads/master@{#35334}

[mike3, 2016-04-06 14:41:52]

I initially wrote parser tests for this, but I had to remove them. They relied
on an error that is not currently detected by the preparser (early errors from
lexical binding redeclarations).

I'd be happy to include parser tests, but I haven't been able to think of any
other way to detect this bug before execution.

[adamk, 2016-04-07 00:00:00]

adamk@chromium.org changed reviewers:
+ caitpotter88@gmail.com

[adamk, 2016-04-07 00:00:00]

This sounds right to me, but adding Caitlin as the original author of this code.

I'm not too worried about testing this in test-parsing.cc, the behavioral tests
are far more important.

[caitp (gmail), 2016-04-07 00:10:22]

On 2016/04/07 00:00:00, adamk wrote:
> This sounds right to me, but adding Caitlin as the original author of this
code.
> 
> I'm not too worried about testing this in test-parsing.cc, the behavioral
tests
> are far more important.

I was looking at this earlier--I think this should be okay, but I think there
was also some reason I didnt do this before. If tests are still passing, lgtm

[adamk, 2016-04-07 00:20:30]

Okay, I started some try runs.

[adamk, 2016-04-07 00:20:57]

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

[commit-bot: I haz the power, 2016-04-07 00:21:03]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1859423002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1859423002/1

[adamk, 2016-04-07 00:38:56]

This lgtm based on the bots so far and some code examination. Thanks for the fix
and the tests.

[commit-bot: I haz the power, 2016-04-07 01:02:58]

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

[commit-bot: I haz the power, 2016-04-07 01:02:59]

Dry run: This issue passed the CQ dry run.

[mike3, 2016-04-07 13:18:59]

The CQ bit was checked by mike@mikepennisi.com

[commit-bot: I haz the power, 2016-04-07 13:19:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1859423002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1859423002/1

[commit-bot: I haz the power, 2016-04-07 13:25:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-07 13:27:03]

Description was changed from

==========
[es6] Fix bug in pattern re-writing

As originally implemented, a SingleNameBinding within a BindingPattern
was incorrectly interpreted as an assignment if an initializer was
present and that initializer was itself an AssignmentExpresion.
For example:

    let x;
    { let [x = y = 1] = []; }
    print(x); // expected: undefined, actual: 1

Extend the heuristic that detects the "context" of a destructuring
pattern to account for AssignmentExpressions within SingleNameBindings.

BUG=v8:4891
LOG=N
R=adamk@chromium.org
==========

to

==========
[es6] Fix bug in pattern re-writing

As originally implemented, a SingleNameBinding within a BindingPattern
was incorrectly interpreted as an assignment if an initializer was
present and that initializer was itself an AssignmentExpresion.
For example:

    let x;
    { let [x = y = 1] = []; }
    print(x); // expected: undefined, actual: 1

Extend the heuristic that detects the "context" of a destructuring
pattern to account for AssignmentExpressions within SingleNameBindings.

BUG=v8:4891
LOG=N
R=adamk@chromium.org

Committed: https://crrev.com/9acbca18456c6d4b704f0e98004d2c78795602fe
Cr-Commit-Position: refs/heads/master@{#35334}
==========

[commit-bot: I haz the power, 2016-04-07 13:27:04]

Patchset 1 (id:??) landed as
https://crrev.com/9acbca18456c6d4b704f0e98004d2c78795602fe
Cr-Commit-Position: refs/heads/master@{#35334}

[mike3, 2016-04-07 13:56:31]

Thank you, Adam! Thank you, Cait!

[caitp (gmail), 2016-04-07 14:44:57]

On 2016/04/07 13:56:31, mike3 wrote:
> Thank you, Adam! Thank you, Cait!

Thanks for the fix =)