1605143 - Derived class constructors always marked as having unknown properties

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect, P3)

Description

[André Bargull [:anba]]

Derived class constructors created via FunWithProtoOperation are always getting marked as having unknown properties, because CloneFunctionObjectIfNotSingleton calls the generic SetPrototype function:

js> dumpObject(class extends class {} { constructor() {} })
object 32844fd80f60
  global 32844fd7b060 [global]
  class 5559473467e8 Function
  group 32844fd78850
  flags: inDictionaryMode hasShapeTable
  proto <unnamed function (typein:1) at 32844fd80fb0>
  properties:
    [Latin 1]"prototype": <Object at c79a9000550> (shape 32844fd9d970 readonly permanent slot 0)

I wonder if it's possible to replace the SetPrototype call with JSObject::splicePrototype (change).

Try looks green with this change applied, but I'm not sure if there are any pitfalls lurking elsewhere: https://treeherder.mozilla.org/#/jobs?repo=try&revision=cf36196aee915762335915ef2e29465c88e8ecca

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1605143 - Part 1: Splice prototype to ensure we don't mark the object as having unknown properties. r=jandem!

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1605143 - Part 2: Fold JSOp::SuperFun to ensure inlined class constructors use `MCreateThisWithProto`. r=jandem!

Depends on D58803

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/fa3ca6fd6f40
Part 1: Splice prototype to ensure we don't mark the object as having unknown properties. r=jandem
https://hg.mozilla.org/integration/autoland/rev/ab8ec6eab00c
Part 2: Fold JSOp::SuperFun to ensure inlined class constructors use `MCreateThisWithProto`. r=jandem

Comment 4

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/fa3ca6fd6f40
https://hg.mozilla.org/mozilla-central/rev/ab8ec6eab00c

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Since the status are different for nightly and release, what's the status for beta?
For more information, please visit auto_nag documentation.