That proposal is really dragging though. And typescript needs as much work because that's where the real power is. We need discern thing like

    match (x) {
      "bob": ...,
      string: ...,
      () => Promise<void>: ...,
      () => Promise<string>: ...,
    }

Discriminating a function or promise based on return type is never going to work, because JavaScript is dynamically typed and TypeScript erases types at compile time, so there's no way to know at runtime what type a function or promise is going to return.