Bug in GNAT GPL 2006?

["(see below)" <yaldnif.w@blueyonder.co.uk>]

Using GNAT GPL 2006 (20060522-34) I get warning messages
like the following when using extended return statements:

    function is_empty (the_table : a_safe_table) return Boolean is
    begin
       return result : Boolean do
              |
 >>> warning: variable "result" is assigned but never read

          lock_table;
             result := is_empty(a_basic_table(the_table));
          unlock_table;
       end return;
    end is_empty;

I'm inclined to assume that this is a compiler bug, but can
anyone more knowledgeable about Ada 200[57] confirm this?

-- 
Bill Findlay
<surname><forename> chez blueyonder.co.uk