Proposal: user defined attributes

[Manu]

On 16 March 2012 16:51, Adam D. Ruppe <destructionator at gmail.com> wrote:

> On Friday, 16 March 2012 at 14:11:35 UTC, Manu wrote:
>
>> Surely the term you're looking for here is @annotate(...) ?
>>
>
> Meh, I don't care that much about names. I went
> with "note" anticipating people would complain about
> @add_user_defined_attribute() being too long :)
>
>
>
>  What if you want to annotate with a variable?
>>
>
> That *might* work because a variable is an expression too.
> I'm not sure though. Will probably have to implement to
> know for sure.
>
> Of course, a constant can be represented as a struct
> for name and value:
>
> struct Description { string s; }
>
> @note(Description("yada yada yada")) int a;
>
>
>
>  Surely this is just as easy: @modulename.attribute int myThing;
>>
>
> Yeah, I think so. I remember this being a counterpoint
> last time we talked about it, but I don't recall the
> specific argument made.
>
>
>  Perhaps that's the key distinction between 'annotation' and a 'custom
>> attributes' .. an annotation this way is a shared compile time constant,
>> associating with its type info, as you suggest. A custom attribute is an
>> instance-specific association vontaining variable data.
>>
>
> Yeah, "annotation" might be the better word. That's
> what I want here, but too late to change the subject name
> now.
>
>
>  attribute myAttribute
>>
>
> I think this could be done as a struct, but I haven't
> used this kind of attribute at all so not sure...
>
> But what I'm thinking is:
>
> struct myAttribute(Type) {
>   Type value;
>   alias value this;
>
>   bool bNeedsAttention;
>   @property void refresh(bool bRefresh) { bNeedsAttention = bRefresh; }
> }
>
> myAttribute!int thing;
> thing.refresh = true;
>
> and thing can be substituted for an int anywhere else.
>

Interesting approach, how will that affect 'thing's type?
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