Version 1.2 of ai05s/ai05-0025-1.txt

!topic Missing rule about overloaded subprograms in 12.7
!reference RM05 12.7, 12.3
!from Adam Beneschan 06-11-03
!discussion

I believe that there's an omission regarding the new formal package
syntax.  Suppose you declare a generic with two formal subprograms
with the same defining name:

    generic
        type T1 is private;
        type T2 is private;
        with function "=" (Left, Right : T1) return Boolean is <>;
        with function "=" (Left, Right : T2) return Boolean is <>;
    package GP1 is
        ...
    end GP1;

For an instantiation, 12.3(9) says, "If two or more formal subprograms
have the same defining name, then named associations are not allowed
for the corresponding actuals".

Since this paragraph discusses a generic_association, it also would
have covered formal packages in Ada 95.  The syntax for a
formal_package_actual_part was:

    (<>) | [generic_actual_part]

and a generic_actual_part is a list of generic_associations, so the
same rule in 12.3(9) would have applied here too.

But that's no longer true.  The new syntax for a
formal_package_actual_part is

    ([others =>] <>) | [generic_actual_part] |
    (formal_package_association {, formal_package_association} 
     [, others => <>])

where a formal_package_association is either a generic_association or:

    generic_formal_parameter_selector_name => <>

The rule in 12.3(9) still applies to the generic_associations, but
there isn't any similar rule that applies to 

    generic_formal_parameter_selector_name => <>

So nothing seems to make it illegal to say

    generic
        type T1 is private;
        type T2 is private;
        with package The_Pak1 is new GP1
             (T1 => T1, T2 => T2, "=" => <>, "=" => <>);
    package GP2 is ... end GP2;

This looks like an omission to me.

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From: Randy Brukardt
Date: Friday, November 3, 2006 10:21 PM

Yup. There doesn't seem to be clear counterpart of 12.3(9-10) at all. We
caught part of it with 12.7(3.2/2), and, as you say, the rules about
associations still are true, but we didn't do any part of 12.3(9-10) for the
box associations.

I find it worse that we never said that the
generic_formal_parameter_selector_name in a box association must match a
name of a formal parameter; 12.3(9) has the right wording but it doesn't
apply because it says "in a generic_association". Nor is there any
completeness check. So it appears that

     generic
         type T1 is private;
         type T2 is private;
         with package The_Pak1 is new GP1
              (T1 => T1, T2 => T2, Blob => <>, Glarch => <>,
               "=" => <>, "=" => <>);
     package GP2 is ... end GP2;

is also legal.

The annoyance here is that we didn't syntactically name
"generic_formal_parameter_selector_name => <>"; the lack of doing so already
led to awkward wording like "as well as associations with <>". If we had
done that, we could just copy 12.3(9) here with appropruate changes. Sigh.

It's not clear to me if 12.3(10) is covered by the existing wording, either;
I don't think so (matching is something else altogether). Surely we don't
want to allow:

   (T1 => T1, T2 => <>, T2 => T2, others => <>)

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