DIP6: Attributes

[Andrei Alexandrescu]

Steven Schveighoffer wrote:
> On Tue, 04 Aug 2009 12:23:41 -0400, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> Steven Schveighoffer wrote:
>>> On Tue, 04 Aug 2009 09:45:51 -0400, grauzone <none at example.net> wrote:
>>>
>>>> Steven Schveighoffer wrote:
>>>>> don't think it's worth adding them until we can have full 
>>>>> reflection capabilities so we can get at elements of code and 
>>>>> therefore get the annotations associated with it.  I see much more 
>>>>> usefulness for annotations as reflection hints than as a 
>>>>> replacement for keywords.
>>>>
>>>> But we already have full reflection. It's called __traits. You can 
>>>> build a serialization library or "proper" (user friendly?) 
>>>> reflection on top of it.
>>>  I think you are the 1 millionth person to say it, and yet we still 
>>> do not have a "user friendly" reflection system.  Why is that?  You'd 
>>> think that if it could be done, somebody would have done it by now.
>>
>> The reality is there's quite few of us. D is not in the stage where if 
>> something could be done, somebody somewhere has done it or is working 
>> on it.
>>
> 
> That's understandable, nobody can expect a language as young as D to 
> have everything.
> 
> But in reality, I think the *theory* that everything is there to build a 
> reflection system is only proven when it actually happens.  I'm sure 
> when the enterprising person or persons go to develop it, they will find 
> pieces missing from the static reflection system.

Exactly. I'm absolutely sure there are quite a few things needed here 
and there. I can assure you I'll push hard for those.

> So my point is that adding annotations before reflection works and is 
> implemented makes little sense to me, because the usage of them will be 
> crippled by the fact that reflection isn't complete.
> 
> What I'd like to see is something like this possible:
> 
> void foo (int timeout, string bar, float f = 4.0);
> 
> void foo(int timeout);
> 
> call!(foo)("timeout=5,bar=\"hello\"");
> 
> Taking into account the default value of f, what the parameters are 
> named, and which overload to call.  I could certainly do it with C#.

This is interesting. It means we'd need reflection for parameter names, 
which currently does not exist.


Andrei