Generated async / await code is missing require statement #5998

declare module 'bluebird' {
    interface Promise<T> {
        then<U>(onFulfilled: (value: T) => U, onRejected: (reason: any) => U): Promise<T>;
    }

    var Promise: {
        new<T>(resolver: (resolve: (value: T) => void, reject: (reason: any) => void) => void): Promise<T>;
    }   
}

import * as bluebird from 'bluebird';

async function firstName(): bluebird.Promise<string>  {
    return "Dirk";
}

async function lastName(): Promise<string> {
    return "Baeumer";
}

async function use() {
    var first = await firstName();
    var last = await lastName();
    return `${first} ${last}`;
}

if (require.main === module) {
    var p = use();
    p.then((value) => console.log(value));
}

var  bluebird = require('bluebird');