Transpiled async generators return a promise value with `yield*` and rejected promise values

[falsandtru]

@agentcooper Could you also fix this?

TypeScript Version: 2.9.0-dev.20180509

Search Terms:

Code

(async function () {
  async function* g() {
    yield* [Promise.reject(0)];
  }
  try {
    const iter = g();
    console.log(0, await iter.next());
  }
  catch (r) {
    console.log(1, r);
  }
})();

Expected behavior:

Outputs 1, 0, Chrome works so.

Actual behavior:

Outputs 0, Object{value: Promise{}, done: false}.

Playground Link:

Related Issues: #23887

[mhegazy]

@rbuckton can you take a look.

[falsandtru]

any blocking issues?