abstract class Original {
    constructor() {}
    get info() {return 'X';}
    getData(key: this['info']) {}
    setData(key: this['info'], value ) {}
}

class MyClass extends Original {
    get info() {return 'A' as 'A';}
}
class MyOtherClass extends Original {
    get info() {return 'B' as 'B';}
}
const myInstance = new MyClass();
console.log(myInstance.getData('A'));

const myOtherInstance = new MyOtherClass();
console.log(myOtherInstance.getData('B'));