1233040 - ArrayBuffer.prototype.slice does not respect subclassing

Status: RESOLVED DUPLICATE of bug 1165053

(Core :: JavaScript Engine, defect)

Description

[Lars T Hansen [:lth]]

Consider:

Also see bug 1233011, bug 1232966 for analogous cases for SharedArrayBuffer and references to (currently pending) test cases.

class MySub extends ArrayBuffer { constructor(n) { super(n) } }
var m = new MySub(10)
m.byteLength             // 10
m instanceof ArrayBuffer // true
m instanceof MySub       // true
var xx = m.slice(0,5)
xx instanceof MySub      // ***false***

Almost certainly that last one should be true, cf ES6 24.1.4.3, steps 13 and 15, which will use SpeciesConstructor to pick up a constructor that is appropriate to the "this" object, which is a MySub.

Comment 1

[Lars T Hansen [:lth]]

A dup of part 11 of the monster bug :arai is working on.

Comment 2

[Lars T Hansen [:lth]]

Groan, 1165052 is about Array (only), not ArrayBuffer.

Comment 3

[Tooru Fujisawa [:arai]]

apparently fixed by bug 1165053, and the testcase in comment #0 returns true now.

also, there are some more testcases about subclassing added by the patch there, so I think we can just close this bug.
https://hg.mozilla.org/mozilla-central/rev/35e1fd91ca89