Narrowing is not invalidated when side effects occur outside of current scope

[bgnx]

Why is there an error?

TypeScript Version: 2.6.0-dev.20171015

Code

enum SomeEnum {
    k1 = 1,
    k2 = 2,
    k3 = 3
}

class SomeClass {
    state: SomeEnum = SomeEnum.k1
    method() {
        if (this.state === SomeEnum.k1) {
            maybeUpdate();
            //error - [ts] Operator '===' cannot be applied to types 'SomeEnum.k1' and 'SomeEnum.k2'.
            if (this.state === SomeEnum.k2) {
                this.state = SomeEnum.k3
            }
        }
    }
}

const obj = new SomeClass();
obj.method();
function maybeUpdate() {
    if (Math.random() < 0.5) {
        obj.state = SomeEnum.k2;
    }
}

Expected behavior:
No error
Actual behavior:
wtf error

[ahejlsberg]

See #9998.

[bgnx]

Ok, how can I disable this optimistic behavior or disable CFA completely ? (I am really against of this dirty hack of making temporary function to escape cfa in if statement)

[RyanCavanaugh]

There isn't a way to disable this behavior. You can use a type assertion, e.g. if (<SomeEnum>this.state === SomeEnum.k2)

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.