1608809 - Make super() throw after evaluating args

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Yulia Startsev [:yulia]]

As discussed at tc39:

https://github.com/tc39/notes/blob/master/meetings/2019-12/december-3.md#normative-make-super-throw-after-evaluating-args

Further details: https://github.com/tc39/ecma262/issues/1351

Extending null has a different behavior depending on if you use class syntax or setPrototypeOf.

we currently throw BEFORE evaluating args on super, we will need to throw AFTER evaluating args on super.

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1608809 - Part 1: Don't throw for non-constructors in JSOp::SuperFun. r=jandem!

Modify JSOp::SuperFun to only retrieve the prototype without any further checks.

Drive-by change:
Take advantage that the object whose prototype gets retrieved is guaranteed to
be a JSFunction, so we neither have to worry about proxy objects nor lazy
prototypes.

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1608809 - Part 2: Remove unnecessary rooting in JSOp::InitHomeObject interpreter implementation. r=jandem!

Depends on D60677

Comment 3

[André Bargull [:anba]]

Attachment: Bug 1608809 - Part 3: Remove lazy-proto code paths from JSOp::SuperBase implementations. r=jandem!

The [[HomeObject]] slot is guaranteed to either contain a JSFunction or a
PlainObject, so we can use safely use JSObject::staticPrototype() to retrieve
the prototype and can also remove the lazy-proto handling in the compilers.

Depends on D60678

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c79dd9a939fd
Part 1: Don't throw for non-constructors in JSOp::SuperFun. r=jandem
https://hg.mozilla.org/integration/autoland/rev/dc2a6717541a
Part 2: Remove unnecessary rooting in JSOp::InitHomeObject interpreter implementation. r=jandem
https://hg.mozilla.org/integration/autoland/rev/b77cdd2e0b00
Part 3: Remove lazy-proto code paths from JSOp::SuperBase implementations. r=jandem

Comment 5

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/c79dd9a939fd
https://hg.mozilla.org/mozilla-central/rev/dc2a6717541a
https://hg.mozilla.org/mozilla-central/rev/b77cdd2e0b00