interface IThenable<T extends @Nullable Object> {
  <V extends @Nullable Object> IThenable<V> then(
      @JsOptional @Nullable IThenOnFulfilledCallbackFn<? super T, ? extends V> onFulfilled,
      @JsOptional @Nullable IThenOnRejectedCallbackFn<? extends V> onRejected);

  @JsFunction
  interface IThenOnFulfilledCallbackFn<T extends @Nullable Object, V extends @Nullable Object> {
    V onInvoke(T p0);
  }

  @JsFunction