In practice, a lot of stuff has already implemented this using forwards-compatible polyfills. Most of the backend NodeJS ecosystem, for example, already support

In practice, a lot of stuff has already implemented this using forwards-compatible polyfills. Most of the backend NodeJS ecosystem, for example, already supports a lot of this, and you have been able to use this feature quite effectively for some time (with a transpiler to handle the syntax). In fact, I gave a couple of talks about this feature last year, and while researching for them, I was amazed by how many APIs in NodeJS itself or in common libraries already supported Symbol.dispose, even if the `using` syntax wasn't implemented anywhere. I suspect it's going to be less common in frontend code, because frontend code normally has its own lifecycle/cleanup management systems, but I can imagine it still being useful in a few places. I'd also like to see a few more testing libraries implement these symbols. But I suspect, due to the prevalence of support in backend code, that will all come with time.