interface Stuff {
  a?: () => Promise<number[]>;
  b: () => Promise<string>;
  c: () => Promise<string>;
  d: () => Promise<string>;
  e: () => Promise<string>;
  f: () => Promise<string>;
  g: () => Promise<string>;
  h: () => Promise<string>;
  i: () => Promise<string>;
  j: () => Promise<string>;
  k: () => Promise<number>;
}

function foo(): Stuff | Date {
  return {
    a() { return [123] },
    b: () => "hello",
    c: () => "hello",
    d: () => "hello",
    e: () => "hello",
    f: () => "hello",
    g: () => "hello",
    h: () => "hello",
    i: () => "hello",
    j: () => "hello",
    k: () => 123
  }
}