async computed transformed into invalid getter

[jrjohnson]

import { computed } from '@ember/object';

const Foo = EmberObject.extend({
  authors: computed('post.comments.authorName', async function () {
    let comments = await this.post.comments;
    return comments.mapBy('authorName');
  }),
});

is transformed into:

import classic from 'ember-classic-decorator';
import { computed } from '@ember/object';

@classic
class Foo extends EmberObject {
  @computed('post.comments.authorName')
  async get authors() {
    let comments = await this.post.comments;
    return comments.mapBy('authorName');
  }
}

However the best info I can find indicates async get permissions() { is not valid syntax.

I'm actually not sure what the best syntax would be for this. Maybe return a Promise wrapped async function? Or an async observer that sets a tracked property?