accessibility check failed

[Serge Robyns <serge.robyns@gmail.com>]

I'm facing a "mysterious" accessibility check failed error.

I'm having the following function:

   overriding function Get_Client
     (Self        : not null access T_Data_Store;
      Client_Name : in              T_Client_Name)
      return T_Client'Class
   is
      Cursor : Client_Map.Cursor;
   begin
      Cursor := Self.Clients.Find (Client_Name);
      if Cursor = Client_Map.No_Element then
         return T_Client_DAO'(No_Client
                                  with Store => Self);
      end if;
      return T_Client_DAO'(T_Client (Client_Map.Element (Cursor))
                               with Store => Self);
   end Get_Client;

The definition of T_Client_DAO is:
   type T_Client_DAO is new T_Client with record
      Store : access T_Abstract_Data_Store'Class;
   end record;

T_Client is the object with is methods.  T_Abstract_Data_Store is the assembly of Factory interfaces (see below for an example).

The idea is to return a copy of the client record and store with it a reference to the data store class from which the object came from.  This will allow to use my_object.change_XYZ to update the object and it's representation into the store through that reference.

Researching the web for the accessibility check failed all refers to returning a reference to a local variable which is indeed disappearing on the execution of the return statement.  But in my case, I'm just storing the reference I did receive from the parent.

I did find a suggestion to replace anonymous access types to named ones but that does not compile for the interface class for which the above function is an implementation.
 
   type Factory is limited interface;
   type Factory_Access is access Factory;

   function Get_Client
     (Self        : Factory_Access;
      Client_Name : in T_Instrument_Name)
      return T_Client'Class
     is abstract;

with:
warning: abstract subprogram is not dispatching or overriding

However when using not null access T_Factory instead it does compile.