Missing type guard with Arrays

[HolgerJeromin]

TypeScript Version: 1.8.0

Code

var myAny: any = 'anythinghere';

if (Array.isArray(myAny)) {
    var newarray: string = myAny;
}

Expected behavior:
myAny should be of type any[] and not any after the check.
Tested with Visual Studio 2015 Update 2 and TypeScript Playground mouse hover.
And compile should break.

[kitsonk]

any is never narrowed... expected TypeScript behaviour

If the type was any[] | string then it could be narrowed.

[HolgerJeromin]

OK, thanks for the explanation.
Can we change that? :-)

[kitsonk]

Changing any to be narrowed would be a gigantic breaking change. In order to have TypeScript be compatible with JavaScript, it needs a universal top type like any. If you want to keep it from not accepting any value, don't assign that as the variable type.

Why is assigning a type other than any a challenge/issue?

[DanielRosenwasser]

Can we change that? :-)

Unfortunately, as @kitsonk said, it broke a lot for when people do something like myAny instanceof Object, because you basically can't get any distinct information off of an Object.

See #5011 for when I tried to address this.

[HolgerJeromin]

Thanks everyone!