Re: casecrash: language lawyers: C'mon!

[Philip Anderson <phil.anderson@amsjv.com>]

Martin Dowie wrote:
> 
> I think what the original poster is getting at is that it
> would seem perfectly obvious that the case statement is
> referring to the data object called 'H' rather than the
> enumerate 'H', so why can't the language be defined to
> spot this case?

That I think was his question.  But it's not actually the problem the
compiler found, which was the illegal declaration of the object H
(because it is a homograph of the enumeration H).

And that rule is IMHO well-founded, since there are contexts when
writing H would be ambiguous.


Nearer to the original question would be the following:

with Ada.Text_Io; use Ada.Text_Io;
procedure Casecrash is

   package Local is
      type Record_Type is (A, B, C, D, E, F, G, H, I, J, K, L, Unknown);
   end Local;

   use Local;

   type Header is
      record
         Id_Letter : Record_Type := Unknown;
      end record;

   H : Header;

begin
   case H.Id_Letter is
      when A =>
         Put ("a");
      when H =>
--H is not static [RM_95 3.8.1(8); 5.4(5)]
--H is not a value of Record_Type
         Put ("h"); -- H conflict, name clash?
                    -- no context resolution?
      when others =>
         Put ("*");
      end case;
end Casecrash;

since H the enumeration literal has been overriden by the H the object,
although the (Rational Apex) compiler is happy with A in this context. 
RM 8.4(10) seems to apply here.


-- 
hwyl/cheers,
Philip Anderson
Alenia Marconi Systems
Cwmbr�n, Cymru/Wales