custom attribute proposal (yeah, another one)

[Timon Gehr]

I think this proposal should be merged with Johannes' one.

On 04/06/2012 11:41 AM, Johannes Pfau wrote:
> Declaring a custom attribute:
> ---------
> module std.something;
>
> struct Author
> {
>     string name;
>     public this(string name)
>     {
>         this.name = name;
>     }
> }
> ---------
>
> Using it:
> ---------
> import std.something; //Usual namespace lookup rules apply to attributes
>
> /*
>  * @Author(param) calls the constructor of the Author struct and
>  * attaches the struct instance to test. Probably @Author (without
>  * parenthesis) coud be made to mean std.something.Author.init
>  */
> @Author("Johannes Pfau") int test;
> ---------
>
> Attaching attributes multiple times as in C# should be possible.
>
> Using reflection to get that attribute:
> ---------
> if(__traits(hasAttribute, test, std.something.Author))
> {
>     Author[] authors = __traits(getAttribute, test,
>         std.something.Author);
> }
> ---------
>
> An array is used here to support attaching the same attribute multiple
> times. Of course "auto authors = ..." should be usable here too.