Fix comparaison between optional list when one is None

[MangelMaxime]

Fix #3617

The error actually comes from:

Because the code expect xs_1 and ys_1 to be list. But because the def equal in util.py doesn't capture the Some .. vs None difference early, then we try to access .tail on a None value.

I believe JavaScript implementation does something similar to capture these case early (line 474 - 476)

Fable/src/fable-library/Util.ts

Lines 471 to 489 in 8ee247a

	export function equals<T>(x: T, y: T): boolean {
	if (x === y) {
	return true;
	} else if (x == null) {
	return y == null;
	} else if (y == null) {
	return false;
	} else if (isEquatable(x)) {
	return x.Equals(y);
	} else if (isArrayLike(x)) {
	return isArrayLike(y) && equalArrays(x, y);
	} else if (typeof x !== "object") {
	return false;
	} else if (x instanceof Date) {
	return (y instanceof Date) && compareDates(x, y) === 0;
	} else {
	return Object.getPrototypeOf(x)?.constructor === Object && equalObjects(x, y);
	}
	}

I am not sure what a is b does in Python, so I let it there and disabled the None, None check as it was already handled by a is b.

Also, I can't "fix" List.equal definition because this is coming from List.fs so I expect that it's implementation is correct and behaving the same as in FSharp.Core

[dbrattli]

Very nice. I took the liberty to move all the test logic inside the match statement. Btw a is b in Python is the same as reference equals, i.e points to the same object. There's only one None instance so all Nones are the same reference.

[MangelMaxime]

I took the liberty to move all the test logic inside the match statement.

You did good.

Thanks for explanation for a i b