1121391 - Update Array.from to match the spec

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, defect)

Description

[ziyunfei]

Array.from({[Symbol.iterator]:0})
>typein:1:0 TypeError: usingIterator is not a function

I'm going to fix this when we add GetMethod() in bug 896608.

Comment 1

[ziyunfei]

Attachment: bug-1121391-v1.patch

Comment 2

[Till Schneidereit [:till]]

Comment on attachment 8549385 [details] [diff] [review]
bug-1121391-v1.patch

Review of attachment 8549385 [details] [diff] [review]:
-----------------------------------------------------------------

Excellent, r=me with the one comment addressed.

::: js/src/builtin/Array.js
@@ +762,4 @@
>      }
>  
> +    // Step 7 is an assertion: items is not an Iterator. Testing this is
> +    // literally the very last thing we did, so we don't assert here.

Ok, after filing https://bugs.ecmascript.org/show_bug.cgi?id=3525 and then marking it as invalid, I see that this still holds. However, the comment doesn't reflect reality anymore: we did just test this as far as actual control flow goes, but the reason for it being impossible to reach this point if `items` is an Iterator is more subtle.

I think we should just add the assert to make it clear that this actually does hold. Dumb people like me might need a moment to understand why, but at least they'd be certain it does.

Comment 3

[ziyunfei]

Attachment: review comment addressed

Comment 4

[Till Schneidereit [:till]]

Comment on attachment 8549610 [details] [diff] [review]
review comment addressed

Review of attachment 8549610 [details] [diff] [review]:
-----------------------------------------------------------------

Yup. No need to re-request a review if you have an "r+ with feedback addressed". (Yes, I did request a further change here, but landing without that change would've been ok.)

::: js/src/builtin/Array.js
@@ +762,4 @@
>      }
>  
> +    // Step 7.
> +    assert(usingIterator === undefined, "'items' could not be an iterable");

"`items` can't be an Iterator after step 6.g.iv"

Comment 5

[ziyunfei]

Attachment: bug-1121391-v3.patch

Comment 6

[ziyunfei]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=884128306c46

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/26263767b141

Comment 8

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/26263767b141