internal override StackData Push(StackData stackData) => stackData.PushOnto(this);
internal override StackData Push(StackData formerStack) => formerStack.PushOnto(this);
internal override StackData Push(StackData stackData) => stackData.PushOnto(this);
internal override StackData Push(StackData formerStack) => formerStack.PushOnto(this);