DIP6: Attributes

[Daniel Keep]

Don wrote:
> ...
> 
> A question: in C#/Java, can you have annotations on function pointer and
> delegate declarations?
> 
> void foo( int delegate(int) pure dg) {
>   ...
> }
> What would this look like with annotations?

Well, Java doesn't HAVE delegates and C# doesn't (AFAIK) allow you to
define them inline; they have a special declaration syntax that can't be
used in an expression.

C# would probably look something like:

namespace Blech
{
    [Pure]
    public delegate int Moo(int);

    public class Urk
    {
        public static void foo(Moo dg) {
            ...
        }
    }
}

> (The underlying question is, how do annotations interact with the type
> system?)

I don't think they form part of the type; they're just sort of attached
to that particular declaration.

>> To answer Don's point, there is nothing saying that the compiler can't
>> read attributes and change its behavior.  Of course, those would have
>> to be builtin attributes.
> 
> Yes, but then they're just keywords, with an @ in front. You'd just be
> kidding yourself if you think you've reduced the keyword count.

I suspect the reasoning goes like this:

* I want attributes.  Walter doesn't see the use.
* Walter complains about adding keywords.
* I can make keywords look like attributes, and then I get attributes!

:P

>> My opinion on removing existing keywords is -- don't.  There's little
>> to no gain.  Let that ship sail, and concentrate on future keyword
>> proposals.
>>
>> -Steve