Interface problems

Stanislav Blinov stanislav.blinov at
Thu Jan 27 13:24:27 PST 2011

On 01/27/2011 09:27 PM, Mandeep Singh Brar wrote:
> 26.01.2011 16:54, Steven Schveighoffer пишет:
>> This is hardly a solution.  He wants to do value comparison, not
>> identity comparison.
>> The real fix is to make interface assume it is an Object, so it can be
>> implicitly cast to Object, and find another way to implement COM
>> interfaces.  The COM interface "hack" is way outdated and extremely
>> harmful, esp. on OS' who *don't use COM*!  I can't see how the
>> benefits it has outweigh the problems it causes.
> The recent discussion in D group about destructor order brought me to
> yet another question about interfaces.
> Currently, functions that should accept classes as parameters, e.g.
> clear(), accept interfaces as well:
> void clear(T)(T obj) if (is(T == class)) // note the constraint
> { /*...*/ }
> interface I {}
> class A : I {}
> void main()
> {
>       I a = new A; // note that typeof(a) is I, not A
>       clear(a);
> }
> This compiles. But raises a question: how come? If it is assumed that a
> reference to interface is not necessarily a D class instance, then it
> shouldn't. The fact that it compiles even more ambiguates the purpose
> and usage of interfaces.
> I agree with Steven. Having a support for COM, CORBA and so on in the
> language is great, but wouldn't it be better to specify it explicitly?
> Maybe solidify the usage of 'extern' keyword?
> interface D {} // instances are guaranteed to be D Objects
> extern interface E {} // instances may or may not be D Objects (COM and
> alike)
> I mean, it's already there in the language and is described in
> 'Interfacing to C++' in the documentation. Though currently, extern
> interfaces are accepted by is(T == class) constraint as well.
> Second this thought. Interface IMHO are far too basic for a functionality tweak.
> Would also like to understand the way to raise such requests and take them to
> their logical conclusion.
> Regards
> Mandeep
There is bugzilla: You can create enhancement 
requests there along with bugreports.

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