980945 - Typed array constructors should not work without "new" per spec

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Boris Zbarsky [:bzbarsky]]

Per current ES6 spec, this expression:

  Uint8Array()

at global scope should throw, because the this object will not be a Uint8Array object.

Currently Chrome and Safari do what the spec says.  We and IE treat it the same as "new Uint8Array()".

We should either fix this or get the spec fixed (e.g. for Array() the spec allows the variant without "new").

Note that there are extension compat problems here, by the way; the Add-On SDK has stuff like:

  return Uint8Array(TextEncoder(encoding).encode(subject).buffer);

Comment 1

[Boris Zbarsky [:bzbarsky]]

Filed bug 980962 to get our own house in order.

Comment 2

[Tomislav Jovanovic :zombie]

(In reply to Boris Zbarsky [:bz] from comment #0)
> Note that there are extension compat problems here, by the way; the Add-On
> SDK has stuff like:
> 
>   return Uint8Array(TextEncoder(encoding).encode(subject).buffer);

this shouldn't be too big of a problem. this issue is:

a) localized to one module file (plus a unit test)
b) relatively new, "shipped" less then 3 months ago with SDK 1.15
a) in a low-level module, with lesser guarantees for stability (marked 'experimental')
c) introduced with SDK 1.15, which (by default) creates addons that use modules built into firefox

so in my estimate, fixing one file and uplifting it to firefox should not result in too big compat problems.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Ah, didn't realize this part of the SDK was new.  Hopefully none of the addons that include that are using it, then.

Note that I plan to fix this tree-wide in bug 980962.

Comment 4

[Tomislav Jovanovic :zombie]

ah, the product/component of bug 980962 threw me off.

ok, removing dependance and renaming 980989 to our "sync up trees" bug..

Comment 5

[Tom S [:evilpie]]

Chrome already requires `new`. So maybe we can do this now?

Comment 6

[Tom S [:evilpie]]

Attachment: Throw when invoking a typed array constructor without new

Try push https://treeherder.mozilla.org/#/jobs?repo=try&revision=14da7f820040 looks good to me. I hope we can land this without breaking the internet :)

Comment 7

[Eric Faust [:efaust]]

Comment on attachment 8673883 [details] [diff] [review]
Throw when invoking a typed array constructor without new

Review of attachment 8673883 [details] [diff] [review]:
-----------------------------------------------------------------

Thanks!

Comment 8

[Kohei Yoshino [:kohei]]

Added the site compatibility doc: https://www.fxsitecompat.com/en-US/docs/2015/calling-typed-array-constructors-without-new-will-throw/

Comment 9

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/31561a5ce4de

Comment 10

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/f7e8784f32b9

Comment 11

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/31561a5ce4de
https://hg.mozilla.org/mozilla-central/rev/f7e8784f32b9

Comment 12

[Tooru Fujisawa [:arai]]

Updated following documents:
  https://developer.mozilla.org/en-US/Firefox/Releases/44
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int8Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int16Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint16Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int32Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float32Array
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array

Comment 13

[Florian Scholz (Open Web Docs)]

Thanks :arai!