1710433 - [META] Symbols as WeakMap property keys

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Yulia Startsev [:yulia]]

Currently at stage 2

Comment 1

[Alexandre Folle de Menezes]

Proposal now in Stage 3

Comment 2

[Xidorn Quan [:xidorn] UTC+11]

I have the following test code:

const map = new WeakMap();
const key = Symbol();
map.set(key, 42);

It throws error:

Uncaught TypeError: WeakMap key Symbol() must be an object or an unregistered symbol

However, it works fine on both Chrome and Safari, which means there can be compatibility issue arises from it, and the behavior here is inconsistent with this error message, which is very confusing.

Comment 3

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi]]

(In reply to Xidorn Quan [:xidorn] UTC+11 from comment #2)

However, it works fine on both Chrome and Safari, which means there can be compatibility issue arises from it, and the behavior here is inconsistent with this error message, which is very confusing.

Have you turned on the pref "javascript.options.experimental.symbols_as_weakmap_keys" ?
It is still off by default.

Comment 4

[Xidorn Quan [:xidorn] UTC+11]

(In reply to Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi] from comment #3)

Have you turned on the pref "javascript.options.experimental.symbols_as_weakmap_keys" ?
It is still off by default.

No. Should there be a bug tracking this pref change? Also should we have the error thrown adapt to the availability of this feature, and potentially even mention the tracking bug?