`AR.toOption` for `undefined` promise resolutions resulting in `{ BS_PRIVATE_NESTED_SOME_NONE: 0 }`

[josh-]

When using the new AR functions, we've run into a scenario when calling AR.toOption on a promise that has resolved undefined will result in the underlying value being { BS_PRIVATE_NESTED_SOME_NONE: 0 } (where O.None would instead be expected).

For example:

const toOptionTest = async () => {
  const option = await pipe(AR.resolve(undefined), AR.toOption);

  console.log('option is:', option);

  O.match(
    option,
    () => {
      console.log('option is `Some`');
    },
    () => {
      console.log('option is `None`');
    },
  );

  return option;
};

void toOptionTest();

In the above, option is inferred by the Typescript compiler to be O.Option<undefined>, however the following is printed:

2023-12-06 09:15:04 option is: { BS_PRIVATE_NESTED_SOME_NONE: 0 }
2023-12-06 09:15:04 option is `Some`

I would instead expect the "option is `None`" log line to be printed, and the someFn branch of O.match not to have been called.

---

This appears to be an underlying Rescript value which is returned by AR.toOption because Some(value) is called here even if the value is None:

ts-belt/src/AsyncResult/AsyncResult.res

Lines 70 to 72 in c825d97

	promise->thenResolve(option => {
	switch option {
	| Ok(value) => Some(value)

[JUSTIVE]

Hi. I made a PR to resolve this issue. please have a look and let me know if it's right.

[smaspe]

It's not just with AR, though:

The type of:

O.map(value, fn) ?? null

is ReturnType<typeof fn> | null, but in reality it's something like Some<ReturnType<typeof fn>>