TS implicitly typing array in conditional

[JGJP]

let someVar = null as null | number
// other logic here
if ([0, 1].includes(someVar)) {
	// do something
}

Expected behavior:

No problem is returned.

Actual behavior:

TS returns the following problem on someVar in the if statement:

Argument of type 'number | null' is not assignable to parameter of type 'number'.
  Type 'null' is not assignable to type 'number'. ts(2345)

Meanwhile, changing the conditional from [0, 1].includes(someVar) to ([0, 1] as (null|number)[]).includes(someVar) fixes the problem. Why does Typescript implicitly type the array in this instance? The array isn't assigned so won't be used anywhere else, I don't see the utility in requiring this extra syntax here.

It would be nice to be able to use Array.includes() as shorthand for a bunch of || operators such as in someVar === 0 || someVar === 1.

Playground Link:

https://www.typescriptlang.org/play?#code/DYUwLgBAzg9gtiAagQwE4QLwQHYFdjATJQ76EA+pcARiKgFAD0jEMYAFnRMDAOYCWAYwidUIevwBmEABQBtAAwAaCAEYAugDp+2QcFwATEFBmwEKVAEpLEAN70AkMwgGY0eOHY7e9AL5A

Related Issues:

Could not find related issues

[JGJP]

Seems to be a duplicate of #36275