[ES7] Basic support for async functions/methods

[julien-f]

I use them in many projects notably for class methods because the syntax prevents me from easily using workarounds such as Bluebird.coroutine(function * generator() {}).
Unfortunately doing so breaks parsing and prevents EsLint from finding other errors.

I understand that fully implementing async functions could be a lot of work and that it is not a priority to support ES7 features for now but a preliminary support such as simply removing them from the source would at least allows the parsing of the rest of the code.

[lo1tuma]

As mentioned by @nzakas in #125 (comment)

We're not going to implement any ES7 features until they are standardized.

[julien-f]

@nzakas does not seem opposed to implementing this future, as mentioned in eslint/eslint#1657 (comment):

If you want it, consider adding support to Espree: https://github.com/eslint/espree.

We will get to it, but it's low priority for the core team based on getting the rest of ES6 done. You can make it go faster by contributing. :)

I personally don't know how to implement it and I understand it can be much work, that's why I thought it would be worth proposing a intermediary solution.

[nzakas]

I can speak for myself here: we aren't implementing experimental features. If you need such support in ESLint, you can use babel-eslint.

[nickpoorman]

This is no longer experimental, is in stage 2, and implemented in Edge. I'm thinking it might be time to support async.

[xjamundx]

Stage 3 even? tc39/ecma262@2fa3ca4

[xjamundx]

Though i assume this will get swallowed up by #200

[egoroof]

Want this too. 😢 Currently I use babel-eslint which isn't a good solution - eslint parses transpiled code which I didn't write and catches errors in that.

[benjamine]

+1, would love to avoid babel-eslint to use async/await :'(

[not-an-aardvark]

@benjamine This issue is a bit out-of-date; if you're using ESLint 3.6.0 or higher, you can now use parserOptions: {ecmaVersion: 8} in your config to enable async/await.