Problem with instantiating generic procedure

[mgk25@cl.cam.ac.uk (Markus Kuhn)]

Sorry, but after searching through the RM for almost an hour, I still
haven't figured out what I do wrong here and how I should fix this.
I declare in a package spec a procedure A and I want to implement the
procedure body of A by instantiating a generic procedure G. The following
is the shortest possible program that reproduces my problem:

-- bug.ads --
package Bug is
   
   procedure A;
   
end Bug;
-- bug.adb --
package body Bug is
   
   generic
   procedure G;
   
   procedure G is
   begin
      null;
   end G;
   
   procedure A is new G;
   
end Bug;
-------------

GNAT 3.11p on Linux insists on the following error message:

bug.adb:1:14: missing body for "A" declared at bug.ads:3
bug.adb:11:14: "A" conflicts with declaration at bug.ads:3

What is wrong with simply implementing a procedure declared
in the spec file in the body file by instantiating it from
a generic procedure of the exact same signature? Both A and G
have no parameters, so how can there be a conflict?

It would be nice if GNAT wrote out explicitely the two conflicting
sides, each time it uses the word "conflict" in an error message.

Any idea what is wrong here?

Markus

-- 
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org,  WWW: <http://www.cl.cam.ac.uk/~mgk25/>