test

main() {
    var subtest = new SomeSubClass();
    doSomething(subtest);
}

void doSomething(dynamic object) {
    if (object is SomeClass) {
        print((object as SomeClass).test());
    }
}

class SomeClass {
    SomeClass();

    bool test() {
        return true;
    }
}

class SomeSubClass extends SomeClass {
    SomeSubClass();

    bool test() {
        return false;
    }
}