Re: very specific question on Ada syntax

[Keith Thompson <kst@cts.com>]

Robert Dewar <robert_dewar@my-deja.com> writes:
> In article <mailman.981007013.11542.comp.lang.ada@ada.eu.org>,
>   comp.lang.ada@ada.eu.org wrote:
> > Florian Weimer wrote:
> >
> > > A character literal is a prefix, taking attributes is
> allowed.  In
> > > contrast, a string literal is not a prefix, see RM 4.1(2)
> and 4.1.4.
> >
> > Compiling the following with Gnat 3.13p gives:
> >
> > package P is
> >
> >   type  T  is ('a', None, 'Z');
> >   type F_T is access function return T;
> >
> >   X: F_T := 'a''Access;
> >   Y: F_T := None'Access;
> >
> > end P;
> >
> >      6.   X: F_T := 'a''Access;
> >                     |
> >         >>> prefix of "Access" attribute must be aliased
> >
> > Is this then a bug?
> 
> No, this is obviously a correct error message. What would
> make you think that this particular usage was legal?

I think the error message would be clearer if it said that the prefix
must not be an intrinsic subprogram.  RM95-6.3.1 says that the calling
convention for an enumeration literal is Intrinsic; 3.10.2 says that
the Access attribute cannot be applied to an intrinsic subprogram.

One source of confusion is that GNAT doesn't complain about
None'Access; presumably this is a bug.  I don't have a recent version
of Gnat installed, so I'll let someone else submit a bug report
(unless it's already been fixed).

-- 
Keith Thompson (The_Other_Keith) kst@cts.com  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center           <*>  <http://www.sdsc.edu/~kst>
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