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#2737 — 12.2.4.2.4 ComprehensionComponentEvaluation, 13.6.4.6 ForIn/OfExpressionEvaluation: Align behaviour for iteration over undefined/null?

• bug_id: 2737
• creation_ts: 2014-04-25 03:22:00 -0700
• short_desc: 12.2.4.2.4 ComprehensionComponentEvaluation, 13.6.4.6 ForIn/OfExpressionEvaluation: Align behaviour for iteration over undefined/null?
• delta_ts: 2014-06-27 13:20:04 -0700
• product: Draft for 6th Edition
• component: technical issue
• version: Rev 23: April 5, 2014 Draft
• rep_platform: All
• op_sys: All
• bug_status: RESOLVED
• resolution: WONTFIX
• priority: Normal
• bug_severity: normal
• everconfirmed: true
• reporter: André Bargull
• assigned_to: Allen Wirfs-Brock
• cc: brendan

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• commentid: 7920
• comment_count: 0
• who: André Bargull
• bug_when: 2014-04-25 03:22:33 -0700

12.2.4.2.4 Runtime Semantics: ComprehensionComponentEvaluation
13.6.4.6 Runtime Semantics: ForIn/OfExpressionEvaluation Abstract Operation

for-of statement iteration follows the legacy for-in statement behaviour w.r.t to undefined/null, that means undefined/null values are silently ignored. Comprehension iteration throws a type error for undefined/null.

It may make sense to give the same behaviour for any for-of iteration, may it be in a for-of statement or in a for-of comprehension. To provide the same behaviour in for-of statement as in for-in statement seems less important.

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• commentid: 8568
• comment_count: 1
• who: Allen Wirfs-Brock
• bug_when: 2014-05-19 18:37:28 -0700

fixed in rev25 editor's draft

made comprehensions do 0 iterations if value of for-of expression is undefined or null to be consistent with for-in/of statements.

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• commentid: 9037
• comment_count: 2
• who: Allen Wirfs-Brock
• bug_when: 2014-06-16 17:10:36 -0700

fixed in rev25 editor's draft

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• commentid: 9106
• comment_count: 3
• who: Brendan Eich
• bug_when: 2014-06-27 09:26:22 -0700

Didn't you reverse this? Reopen, or new bug with bug # citation here?

/be

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• commentid: 9107
• comment_count: 4
• who: Allen Wirfs-Brock
• bug_when: 2014-06-27 13:20:04 -0700

(In reply to comment #3)
> Didn't you reverse this? Reopen, or new bug with bug # citation here?

yes, made the edit yesterday.


This changed was backed out in rev26 along with removing the similar behavior for for-of based upon TC39 review of the issue.

Changing to resolved-wontfix