Re: Visibility of Indexing aspects

["Dan'l Miller" <optikos@verizon.net>]

On Thursday, July 26, 2018 at 3:31:04 PM UTC-5, Shark8 wrote:
> On Wednesday, July 25, 2018 at 6:12:24 PM UTC-6, Randy Brukardt wrote:
> > "Dan'l Miller" wrote in message 
> > news:googlegroups.com...
> > On Wednesday, July 25, 2018 at 2:58:44 PM UTC-5, AdaMagica wrote:
> > >> Much ado about nothing.
> > >>
> > >> The writer of this code erroneously put things in the private part which
> > >> should have been public. There is a compiler bug leaking from privacy
> > >>which seduced the writer into thinking that his wrong code is correct.
> > >>
> > >> The RM is very precise about this, see the references in this thread.
> > >>
> > >> Love's Labours Lost with any further discussion.
> > >
> > >In other words, I made an insightful good point ...
> > 
> > Sounds like babble to me. What's used by the client has to be public, 
> > period.
> 
> But this is legal:
> 
> Package K is
>   Type Example is private;
> Private
>   Type Example is null record;
>   For Example'Size use 4;
> End K;
> 
> Package J is
>   Type Hex is range 16#0#..16#F#
>   with Size => 4;
>    
>   Type Ex_2 is record
>     Item_1 : Hex;
>     Item_2 : K.Example;
>   end record
>   with Size => 8;
> 
> End J;
> 
> > ...
> > >The _LRM_'s forcing of {Reference, Reference_Holder, Container_Array, ...} 
> > >to be public declarations ...
> > 
> > ...is perfectly fine -- there's nothing wrong or dangerous with using them 
> > directly. Indeed, "indexing" is just a shorthand for a longer call involving 
> > Reference -- you're always allowed to make the longer call, just like you 
> > are allowed to put in .all even if you could have omitted it. We went to 
> > substantial lengths to ensure that you can't keep a reference value longer 
> > than the existence of the return object from Reference -- regardless of how 
> > you use the package. (Telling people not to do something is never an 
> > effective technique for safety!)
> 
> But that's not the issue that is being cited in the original post.
> The issue is that all the indexing-attributes are declared/used in the private part and are [apparently]
> being used in the publicly visible part.
> 
> Is this correct?

Yes that is correct regarding the OP, but my replies were requesting what the wonderful Ada vision for the alternative to this so-called “severe bug” are.  So far the only wonderful Ada vision for a better world than the “severe bug” is to chain-migrate •all• the intended-to-be-private declarations of •all• of {Variable_Indexing, Reference, Refence_Holder, Container_Array, …} gratuitously up to a polluted public view to satisfy the gratuitous over-achievement requirement of _AARM_:2016's ¶22/3 of §4.1.6 on page 189 so that the same semantics shall be able to written in 5 different ways (when the programmer overtly considered 4 of the 5 a bad idea), which is a worse vomit of intended-to-be-private declarations into public than what the so-called “severe bug” divulged:

Find (IB,"pear").Data.all := Element'(...); -- Traditional call
IB.Find ("pear").Data.all := Element'(...); -- Call of prefixed view
IB.Find ("pear") := Element'(...); -- Implicit dereference (see 4.1.5)
IB ("pear") := Element'(...); -- Implicit indexing and dereference
IB ("pear").Data.all := Element'(...); -- Implicit indexing only

Apparently in subsequent replies the justifications for this gratuitous over-achievement requirement of mandating 5 different syntaxes of writing the same semantics (even when the programmer considers 4 of them as a bad idea) is:
1) (perceived?) effort reduction by compiler writers
and
2) syntactic-sugar features get a green-lighted free pass but software-engineering principles (e.g., Steelman requirement 3-5B) get prioritized lower, or worse, perhaps are viewed as governing Ada83-only in the dustbin of history.