async function get_things(_: number | undefined) {
    return [0];
}

async function foobar() {
    // The error goes away without the `| undefined`
    let before: number | undefined = undefined;
    // The error goes away without the loop
    for(let i = 0; i < 2; i++) {
        // The error goes away without the async/await
        const results = await get_things(before);
        //       ^ 'results' implicitly has type 'any' because it does not have a type annotation
        //          and is referenced directly or indirectly in its own initializer.
        before = results[0];
    }
}