Re: Anonymous Access and Accessibility Levels

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

On Monday, April 22, 2019 at 6:11:20 PM UTC-4, Randy Brukardt wrote:
> "Jere" wrote in message 
> ...
> > I think that D.The_T has an accessibility level relative to where
> > an object of type D is declared?
> 
> Yes, but there are special rules for allocators, for objects created as 
> return objects, and many other special cases. This area is not for the faint 
> of heart. In fact, it is only for those that like beating their heads 
> bloody.
> 
> As always, I suggest the following rules:
> 
> (1) Do not use anonymous access types unless you absolutely need one of the 
> special capabilities that can only be done with them.
> (2) Under no circumstances, do anything that cannot be checked statically. 
> (So no one should use dynamic accessibility checks of anonymous access 
> parameters or SAOAATs).
> (3) Think three times before depending upon access parameter dispatching and 
> anonymous access-to-subprograms.
>    (A) If you find that you really need these things, complain to the ARG 
> that you should be able to but cannot do these things with named access 
> types. (This limitation is idiotic, as it requires repeating long 
> declarations at every usage.) [I need help getting this fixed!!]
> (4) Keep access types out of visible specifications (since they make memory 
> management much harder, and locks in clients to suboptimal memory 
> managment).
> 
>                                                        Randy.

I can appreciate that.  I'm not talking about exposing any access
types to the client.  However, I am needing to use an access type
and named access types are insufficient in this case.  While I agree
that compile time checking is preferred, Ada does not provide this
capability in all cases and sometimes I have to rely on runtime
checking (which I still believe is better than manual checking).  In 
either case, I am still interested in understanding those specific
things I asked earlier.  In particular, if the issues I outlined
in Test_AA_2 and Test_AA2 GNAT bugs or some special case rule that
I am missing.  Additionally, I was curious if assignment I highlighted
in the main procedure was also a GNAT bug or a special rule.  My
gut says they are bugs, but I am not 100% sure.