1042324 - shumway.js mutating the [[Prototype]] of an object will cause your code to run very slowly

Status: RESOLVED WORKSFORME

(Firefox Graveyard :: Shumway, defect)

Description

[Chris Peterson [:cpeterson]]

The following JS warning is logged in the web console when loading Shumway:

mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create shumway.js:1419

Waldo added this warning in bug 948227.

Comment 1

[Michael Bebenita [:mbx]]

We're aware of this, and hopefully it won't bite us too hard. We mutate the prototype to make TypeScript constructor functions behave like ActionScript classes, thus integrating the two type systems.

Comment 2

[Till Schneidereit [:till]]

Yeah, I benchmarked this a while ago, and it doesn't cause a slowdown in this case.

I disagree with Waldo on whether we should *always* spew this message, fwiw. There are usages of __proto__ that can well be optimized in the engine (essentially, everything that happens in cold code before TI starts recording type information).

Waldo just thinks we should try to fight __proto__ usage, period. I think that's a lost fight and we shouldn't scare devs into thinking our browser is worse here than others.

Comment 3

[Till Schneidereit [:till]]

We don't do this anymore. \o/