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Newsgroups: comp.lang.ada
Date: Sat, 31 Mar 2018 19:07:18 -0700 (PDT)
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Subject: Re: limited agregate and limited components default initialization
From: Jean-Claude Rostaing <00120260a@gmail.com>
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Xref: reader02.eternal-september.org comp.lang.ada:51268
Date: 2018-03-31T19:07:18-07:00
List-Id: <comp.lang.ada>

--
-- Item_type and ITEM_RECORD are NOT meant to be declared uninitialized, ever.
-- So how do I tell this to GNAT so that Item: aliased ITEM_TYPE as a component is allowed ?
-- Implementing List_type with common access types and "type Bla, type Blabla is access Bla, complete declaration" would have been easy, but the private type Smart_Pointers made a hell of it.

with Pointers;

generic
   type Item_Type(<>) is limited private;
package Lists is
   type List_Type is limited private;
   type Item_Accessor (Item: not null access Item_type) is limited private with Implicit_Dereference => Item;
      function Get(Position: in List_Iterator) return Item_Accessor;
private
   type ITEM_ACCESS;
   type Item_Record is limited
      record
         Item: aliased Item_type;
         Next : Item_Access;
         Pred : Item_Access;
      end record;
   package Record_Pointers is new Pointers (Item_type => Item_Record);
   type Item_Access is new Record_Pointers.Smart_Pointers;

   type Item_Accessor (Item: not null access Item_type) is limited record
      REF: ITEM_ACCESS := SET(ITEM_RECORD'(ITEM.all, others => <>));
   end record;

   type List_Type is limited record
      First: Item_Access;
      Last : Item_Access;
      Count : Natural := 1;
   end record;
end Lists;

And what I was pointing your attention at was:
lists.ads:39:49: initialization not allowed for limited types
for: REF: ITEM_ACCESS := SET(ITEM_RECORD'(ITEM.all, others => <>));