Transpiled async generators don't unwrap returned promise values

[falsandtru]

cc @rbuckton

TypeScript Version: 2.9.0-dev.20180515

Search Terms:

Code

await (async function* () { return Promise.resolve(0); })().next()
// also should be covered by tests
await (async function* () { return Promise.reject(1); })().next()

Expected behavior:

Object{value: 0, done: true}

Actual behavior:

Object{value: Promise{}, done: true}

Playground Link:

Related Issues:

[mhegazy]

@rbuckton can you take a look

[falsandtru]

@rbuckton ?