Comparing these two incomparable types does not lead to an error

[lll000111]

No error from this code comparing two incompatible types:

Flow Try Link

function demo (someString: string, someArray: Array<number>): void {
    // ERROR EXPECTED - none received
    if (someArray === someString) {
        // ...
    }
}

someArray can also be some other type, such as number (arguable, if it was "==" instead of "===") or some object type (definitely useless, comparison to a pointer), it does not have to be an array.

My take:

If the types are known I would expect them to be enforced, only an unknown or yet-to-be-refined type should be comparable to (at that point potentially) incompatible types.