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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: generic package with procedure paramter gives "not subtype
 conformant with declaration"
Date: Sun, 01 Oct 2006 08:18:41 +0100
Organization: Pushface
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Put this somewhere (in package avcall I guess)

   type Av_Param_Access
     is access procedure (AList : System.Address;
                          Value : System.Address);

then 

   generic
      type Any_Type is private;
      Av_Param_Instance : Av_Param_Access;
   package avcall.register_type is

Compiles OK (same environment as you), whether it is correct and
whether it works are of course different matters.