export interface Pending {
  done?: false | undefined;
  // 'need_context' is a hack so `yield*` works
  value: "need_context" | "pending";
}
export interface Ready<T> {
  done: true;
  value: T;
}
// NoInfer prevents TS from inferring T as `"need_context" | "pending"`
export type Poll<T> = NoInfer<Ready<T>> | NoInfer<Pending>;
export interface Future<T> {
  [Symbol.iterator](): Future<T>;
  next(...[value]: [] | [Context]): Poll<T>;
  throw(e?: unknown): Poll<T>;
}
export interface Context {
  wake(): void;
  [Symbol.toStringTag]: "Futures.Context";
}