Object with dynamic attribute in fortran

I am programming in Fortran and I need to create an object class that has a dynamic vector as an attribute. Here is a minimal example of what I am trying to achieve.

MODULE my_class
        PRIVATE
        PUBLIC my_object

        ! define my object with a dynamic attribute
        TYPE my_object
                private
                integer:: size;
                real, allocatable:: tab(:); ! here the dynamic vector
        CONTAINS
                private
                final:: destructor;
        END TYPE my_object

        ! define an interface for object constructor
        INTERFACE my_object
                module procedure:: constructor;
        END INTERFACE my_object

CONTAINS

        ! define constructor
        FUNCTION constructor(size) RESULT(obj)
                integer, intent(in):: size;
                type(my_object):: obj;

                obj%size= size;
                allocate(obj%tab(size))
        END FUNCTION constructor

        ! define destructor
        SUBROUTINE destructor(this)
                class(my_object):: this;

                if (allocated(this%tab)) deallocate(this%tab)
        END SUBROUTINE
END MODULE my_class

But I am not sure that is the proper way to do it. Is there not a risk of memory leaking with this implementation in case of multiple initializations? With this code for example :

PROGRAM test
        USE my_class
        IMPLICIT NONE
        type(my_object):: obj;

        obj= my_object(1000);
        obj= my_object(3000);
END PROGRAM test

Has the obj%tab of the first instance been properly deallocated? Or should I reimplement the equal operator?

Thanks for helping me to find out how Fortran deals with this.