public aliases to private/package symbols

[Timon Gehr]

On 01/25/2012 03:56 AM, Nick Sabalausky wrote:
> "Timon Gehr"<timon.gehr at gmx.ch>  wrote in message
> news:jfnlpu$k0p$1 at digitalmars.com...
>> On 01/25/2012 01:59 AM, Peter Alexander wrote:
>>> On Wednesday, 25 January 2012 at 00:08:25 UTC, Timon Gehr wrote:
>>>> Accessibility-raising aliases are trivially safe, because the alias
>>>> declaration must have access to the aliased symbol.
>>>
>>> You are probably right about not introducing holes, but I can imagine
>>> this getting tricky, and perhaps confusing in some cases. Here are some
>>> off the top of my head.
>>>
>>> module A;
>>> private class Foo {}
>>> public alias Foo Bar;
>>>
>>> In other modules that import A:
>>>
>>> Bar b = new typeof(b)(); // typeof(b) is Foo. Is this allowed?
>>>
>>> T foo(T)(T x) { return new T(); }
>>> Bar b;
>>> b = foo(b); // T is deduced to Foo, should this work?
>>>
>>> Bar b = new Bar();
>>> mixin("b = new " ~ typeof(b).stringof ~ "();"); // This fails, the
>>> string is "Foo"
>>>
>>>
>>> Just thinking about this has made me change my position. Accessibility
>>> raising aliases should not be allowed. It's a minefield.
>>
>> That is a valid counter-argument. While I am sure these issues could be
>> sorted out, it would probably amount to over-engineering. This is
>> basically the only useful use case worth considering:
>>
>> private template Tmpl(T){...}
>> public alias Tmpl!int foo;
>>
>> Tmpl and Tmpl!int are two _distinct symbols_, and there is no dedicated
>> syntax to make just one of them accessible.
>>
>> Therefore, this use case could be allowed as a special case: Explicit use
>> of Tmpl from another module would be forbidden, but the instance Tmpl!int
>> would be public under the name foo. (While explicitly instantiating
>> Tmpl!int would fail, because Tmpl is not accessible (or ideally not
>> visible).)
>>
>> There would be no public/private aliasing, and therefore all the issues
>> you mentioned would not exist in this case.
>>
>
> There's no need for special cases. Just don't go de-aliasing symbols. That
> takes care of everything.
>

It does not.

private class A{
     static A factory();
}

public alias A B;

What is typeof(B.factory()) ?