Proposal: user defined attributes

[Jacob Carlborg]

On 2012-03-21 17:00, Adam D. Ruppe wrote:
> On Wednesday, 21 March 2012 at 15:02:15 UTC, Jacob Carlborg wrote:
>> Here's my proposal:
>
> Ah yes, I think I did read that before.
>
> I'm not in love with the key=value or the explicit
> @attribute on the classes, which is the two biggest
> differences we have.
>
> The key=value is nice, but it isn't in the language today,
> so it'd be a bunch of special code in the @attribute parser
> in the compiler.
>
> If we were to have key=value syntax, I say we should do it
> generically (like C style struct initializers?) so it can
> work in regular code too, then pick it up naturally here.

Would "key: value" be possible. The syntax we have for AA literals?

> I'd prefer to use the existing language syntax in there
> so the implementation can literally be as simple as:
>
> if(token == TOKnote) {
> token.next();
> annotations ~= parseExpression();
> }
>
>
> D's existing struct syntax can handle arguments easily
> enough with the StructName("member", "member"); style.
> Reusing that here keeps the implementation simple,
> and it might be more flexible:
>
> enum MyNote = Something("with args", 2);

That would be nice.

> @note(MyNote) int foo;
> @note(MyNote) bool bar;

But I don't like the @note syntax. I really would like this:

@MyNote int foo;


> The other thing is @attribute struct {} rather than just
> struct {}. I don't any benefit to that. If I want to
> reuse a regular, runtime struct to store info at compile
> time, why shouldn't I be able to do that?

I just throw that in because Java has it. Don't know if it's needed or 
not. Java has a kind of special syntax for default values with annotations.

-- 
/Jacob Carlborg