Add async/await sugar on top of generators/yield

[GabrielRatener]

Should CS support async/await sugar on top of generators and yield?

This can be done with little overhead, and seems like sensible sugar to add to the language, since generators and yield are used largely to pause function execution and resolve promises.

[vendethiel]

I don't think we're going to support es7 features before any environment supports it. Wontfix for now.

[GabrielRatener]

What do you mean by environment?

[vendethiel]

Browsers, node, etc.

[GabrielRatener]

I see, what is the motivation for doing this?

[snowyu]

this(Browser and below node 0.11.2) can be supported via regenerator.

So we need async/await now.

[vendethiel]

@jashkenas expressed his intent here: #3073 (comment)

[GabrielRatener]

@vendethiel CS has always implemented features that were not, and still are not in JS. That is the whole point of CS. How would this be any different?

[vendethiel]

No, that's not the case. Features added were not "as ES6" (because those weren't pinned at the time). class, super, do (our let) have different semantics compared to ES6's.

[GabrielRatener]

I am not talking about ES6 features speifically. In general CS has added sugar over JS. Is the only reason to not implement async/await, the fact that a similar feature is in the proposal phase fo ES7?

[jashkenas]

@GabrielRatener If you'd like to see a more serious discussion of this idea happen, please open a pull request with a sketch of how you'd propose to implement async and await on top of generators. Then we can actually talk about it.

[GabrielRatener]

@jashkenas Just opened PR #3757, full proposal, tested and ready to be tried.