1377349 - Remove support for nested destructuring in object rest properties

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[André Bargull [:anba]]

Nested destructuring patterns are no longer allowed in object rest/spread per https://github.com/tc39/tc39-notes/blob/master/es8/2017-05/may-23.md#conclusionresolution-10

Comment 1

[André Bargull [:anba]]

Attachment: bug1377349.patch

Patch to forbid patterns after rest-properties in destructuring contexts. 

The new if-condition in checkDestructuringAssignmentTarget() checks for unparenthesised and parenthesised patterns to avoid displaying the "destructuring patterns in assignments can't be parenthesized" error message.

With the next test262 update we should get new tests to ensure destructuring patterns cannot be used with object rest-properties.

I plan to request uplift for this patch to beta, to ensure our object rest-properties implementation is compliant to the latest spec proposal when we ship this feature in moz55.

Comment 2

[Shu-yu Guo [:shu]]

Comment on attachment 8884854 [details] [diff] [review]
bug1377349.patch

Review of attachment 8884854 [details] [diff] [review]:
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Looks great. Really sorry about the huge review delay.

Comment 3

[André Bargull [:anba]]

(In reply to Shu-yu Guo [:shu] from comment #2)
> Looks great. Really sorry about the huge review delay.

TBH I'm not too happy we've now shipped a version which is no longer compliant with the latest spec proposal, because the whole process from raising the issue, getting an agreement on TC39, having a fixed draft, updating the implementation, and getting it reviewed took quite some time. But I guess there shouldn't be much users' outrage because of this. :-)

Comment 4

[André Bargull [:anba]]

Try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=06f70a56db4dbb89f79f68615a7d8817c6357b4a

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/074fb831cd7b
Remove support for nested destructuring in object rest properties. r=shu

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/074fb831cd7b