MATLAB cannot deal with that for now.
As a small trick, create an instance of your class in the base workspace and go back to writing your actual code.
So for example execute in the command window
And then go to your function you are writing and use "a.<Press TAB>" and you will see that autocompletion works.
In the case you cannot create an instance of your class use .empty this will also work fine:
a = YOURCLASS.empty(1,0);