Refine duplicate arrow function parameter location handling

Refine duplicate arrow function parameter location handling

This patch fixes the logic of finding the location of a duplicate
parameter error in arrow functions by only looking at the error if it
exists. This should address a TSAN error. Further, an UNREACHABLE()
statement is inserted somewhere in the ExpressionClassifier code
to make future similar bugs easier to find.

BUG=v8:4483
Committed: https://crrev.com/29f1475a8d4e8df2198e77f9f2bc1bb92a433435
Cr-Commit-Position: refs/heads/master@{#39701}

[Dan Ehrenberg, 2016-09-24 01:25:41]

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

[commit-bot: I haz the power, 2016-09-24 01:25:50]

Dry run: 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, 2016-09-24 01:31:00]

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

[commit-bot: I haz the power, 2016-09-24 01:31:01]

Dry run: Try jobs failed on following builders:
  v8_win_nosnap_shared_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_nosnap_shared_rel_ng...)
  v8_win_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_rel_ng/builds/14977)

[Dan Ehrenberg, 2016-09-24 01:38:43]

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

[commit-bot: I haz the power, 2016-09-24 01:38:51]

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

[adamk, 2016-09-24 01:44:05]

adamk@chromium.org changed reviewers:
+ adamk@chromium.org

[adamk, 2016-09-24 01:44:06]

lgtm

[Dan Ehrenberg, 2016-09-24 01:44:17]

Description was changed from

==========
Refine duplicate arrow function parameter location handling

BUG=
==========

to

==========
Refine duplicate arrow function parameter location handling

This patch fixes the logic of finding the location of a duplicate
parameter error in arrow functions by only looking at the error if it
exists. This should address a TSAN error. Further, an UNREACHABLE()
statement is inserted somewhere in the ExpressionClassifier code
to make future similar bugs easier to find.

BUG=v8:4483
==========

[Dan Ehrenberg, 2016-09-24 01:45:11]

The CQ bit was unchecked by littledan@chromium.org

[Dan Ehrenberg, 2016-09-24 01:45:12]

The CQ bit was checked by littledan@chromium.org

[commit-bot: I haz the power, 2016-09-24 01:45:22]

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, 2016-09-24 02:07:09]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-09-24 02:07:27]

Description was changed from

==========
Refine duplicate arrow function parameter location handling

This patch fixes the logic of finding the location of a duplicate
parameter error in arrow functions by only looking at the error if it
exists. This should address a TSAN error. Further, an UNREACHABLE()
statement is inserted somewhere in the ExpressionClassifier code
to make future similar bugs easier to find.

BUG=v8:4483
==========

to

==========
Refine duplicate arrow function parameter location handling

This patch fixes the logic of finding the location of a duplicate
parameter error in arrow functions by only looking at the error if it
exists. This should address a TSAN error. Further, an UNREACHABLE()
statement is inserted somewhere in the ExpressionClassifier code
to make future similar bugs easier to find.

BUG=v8:4483

Committed: https://crrev.com/29f1475a8d4e8df2198e77f9f2bc1bb92a433435
Cr-Commit-Position: refs/heads/master@{#39701}
==========

[commit-bot: I haz the power, 2016-09-24 02:07:28]

Patchset 2 (id:??) landed as
https://crrev.com/29f1475a8d4e8df2198e77f9f2bc1bb92a433435
Cr-Commit-Position: refs/heads/master@{#39701}