How to cast to the subclass of a class in an inherited Method?

Question

I want to call methods defined in the parent class that return "this" but I want their return Type to be the child type, not the parent type.
Currently I am using this ugly, inherently error prone technique, where mistakes would only become visible through ClassCast Exceptions...

abstract class AbstractClass<T extends AbstractClass<?>>{
    public T doSomething(){
        return (T)this;
    }
}

class Implementation extends AbstractClass<Implementation>{     
}

// usage
Implementation impl = new Implementation().doSomething().doSomething();

Is there any smarter way to do this?
Does my way (Casting to generic Type) reduce performance compared to implementing a concrete return type in each child class?