!standard 08.03(26/1)                                 04-08-31  AI95-00377/01
!class binding interpretation 04-04-20
!status work item 04-08-31
!status received 04-03-23
!priority Low
!difficulty Medium
!subject Naming of generic child packages

!summary

If a library unit generic and a library unit instance thereof have child
units with the same name, then the explicitly declared child of the instance
hides the implicit declaration corresponding to the child of the generic.

!question

If a library unit generic and a library unit instance thereof have child
units with the same name (see the example), then it would seem that
the instance declares nonoverloadable homographs. Was this intended? (No.)

!recommendation

(See summary.)

!wording

Append to end of 10.1.1(19):

Furthermore, if the instance is a library package, then this declaration
is not visible within the scope of a with_clause that mentions a child
unit of the instance which is a homograph of this declaration.

!discussion

This scenario never occurs in practice. The language needs to be well-defined
and a solution should be chosen which is easy to specify and to implement,
but users really don't care about this one at all.

We do not want to allow a view of an instance which declares
non-overloadable homographs (see, for example, the first sentence of
8.3(26/1)). It seems at least possible that this might requires a bunch of
special-case visibility rules, and that is reason enough to abandon this
approach.

Another approach would be to say that neither of the two declarations are
visible, but the suggested solution seems simpler. In addition, the suggested
solution is consistent with Ada's notion that in general an explicit
declaration hides an implicitly declared homograph.

In the wording section, should "is not visible" be replaced with
"is hidden from all visibility"?

!example

    generic
    package G1 is
    end G1;

    generic
    package G1.G2 is
    end G1.G2;

    with G1;
    package I1 is new G1;

    package Some_Package is
    end Some_Package;

    with Some_Package;
    package I1.G2 renames Some_Package;

    with G1.G2;
    with I1.G2;
    package Q1 renames I1.G2; -- legal? (yes)

    with G1.G2;
    with I1.G2;
    package Q2 is new I1.G2; -- legal? (no)

    with G1.G2;
    with I1.G2;
    with System;
    procedure Q3 (X : System.Address := I1.G2'Address);  -- legal? (yes)

--!corrigendum

!ACATS test

!appendix

From: Stephen W. Baird
Sent: Tuesday, March 23, 2004  12:34 AM

Consider the following example:

    generic
    package G1 is
    end G1;

    generic
    package G1.G2 is
    end G1.G2;

    with G1;
    package I1 is new G1;

    with G1;
    package I1.G2 renames Standard;

    with G1.G2;
    with I1.G2;
    package Q1 renames I1.G2; -- legal?

    with G1.G2;
    with I1.G2;
    package Q2 is new I1.G2; -- legal?

    with G1.G2;
    with I1.G2;
    with System;
    procedure Q3 (X : System.Address := I1.G2'Address);  -- legal?

Should Q1, Q2, and Q3 be rejected?

It seems to me that they should, but RM justification for this position is
not obvious.

In particular, the two "I1.G2" declarations, one a generic package and one
a non-generic package rename, do not appear to be hidden from all
visibility at the points where the name is used.

One might argue that withing  both G1.G2 and I1.G2 implicitly results in a
view of package I1 which violates the first sentence of 8.3(26/1), but
that seems like a stretch.

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