Inconsistent narrowing of 'any' type

[tinganho]

let value1 : string | any;
if (typeof value1 === 'string') {
    value1 // <-- check me
}

let value2: Object | any;
if (value2 instanceof Object) {
    value2 // <-- check me
}

function isString(value: string | any) : value is string {
    return typeof value === 'string';
}
let value3: string | any;
if (isString(value3)) {
    value3 // <-- check me
}

Only the typeof query will narrow to a non-any type above.

[DanielRosenwasser]

I think any being in a union here is unrelated.

You don't want to narrow from any to Object because now you can effectively do nothing with your value. So in general, we don't narrow with instanceof type guards. See #1426 for why.

User-defined type guards need to exhibit the same behavior (because they might internally use an instanceof guard); however, we are considering narrowing from any for primitives, regardless of the type guard you use. See #5930 and #6015.

[tinganho]

Ok thanks @DanielRosenwasser. I have followed the discussion about any narrowing. Didn't know the rule applied to union consisting of type anys too.