```ts class FooBar { foo: number; bar: string; } class Extra extends FooBar { lorem: st

class FooBar {
    foo: number;
    bar: string;
}

class Extra extends FooBar {
    lorem: string;
}

const fooBar: FooBar = new Extra();

class FooBar {
    foo: number;
    bar: string;
}

class Extra extends FooBar {
    lorem: string;
}

const fooBar: FooBar = new Extra();