Re: Preventing private procedure visibility being made public through extension

[Jere <jhb.chat@gmail.com>]

On Monday, May 22, 2017 at 5:17:47 PM UTC-4, Randy Brukardt wrote:
> "Jere" wrote in message 
> ...
> > Definitely.  I am also worried about someone copying the access
> > value and holding onto it past the lifetime of the object. I try
> > to avoid Access types when I can.  I wish there was someway to
> > actually pass a limited type as a function return that didn't
> > involve build in place that can initialize.  I just want to be
> > able to return the limited object out temporarily to access it:
> 
> That's what generalized references are for. See 4.1.5 in the RM.
> 
>                         Randy.

That's a good point. I did end up playing with this and getting
an example working.  After going through Jeffrey's example, I
ended up scrapping the access types altogether, but I do need
to learn to leverage this more in cases where access types 
are necessary.

Side question:

If I have a type (Gnoga'ish example):

type View_Base_Type is new Element_Type with private; --taggeed
type View_Type is new View_Base_Type with private;
procedure Create
  (View   : in out View_Type;
   Parent : in out Base_Type'Class;
   ID     : in     String := "");

-- Excuse any typos, this is hand typed code

And then I extend it:

   type My_Type is new View_Base_Type with private;
   procedure Create
     (Obj    : in out My_Type;
      Parent : in out Window_Type'Class; -- derived from Base_Type'Class
      ID     : in     String := "");

private

   type My_Type is new View_Type with null record;

Sometimes if I subtype or extend My_Type, I get the ambiguous
calls to Create issue due to the inherited Create function
from View_Type.

Since the extension of View_Type was private (I publicly 
extended View_Base_Type), should there still be an 
ambiguity between the Create procedures?  My new
one shouldn't be an override and since the extension
to View_Type is private, it shouldn't be callable
(I'm not in a child package, this would be just
some other unrelated package subtyping or extending
My_Type).  I get that before my extension was public
so making the Create procedure private wasn't an
option, but I had hoped with the full view being
private it wouldn't cause the ambiguity.  I realize
in code that could view the private section the issue
might still be there, but this wouldn't be a package
that can see the private section.