Template args to UDA's

[Kenji Hara]

It looks reasonable, but in general case it would introduce not trivial
semantic issue.

Based on the current D language spec, prefix attribute is just rewritten to
blocked attribute.

@attribute("target", T) void func(string T)() {}

to:
@attribute("target", T) {
    void func(string T)() {}
}

And block attribute can contain other declarations.

@attribute("target", T) {

    enum str = T.stringof;

    void func(string T)() {}
}

Well, if the enhancement is implemented, T would be deduced by the each
call of template function foo. Then the enum value would become
undeterministic.

I think it is not implementable.

Kenji Hara


2013/5/28 Manu <turkeyman at gmail.com>

> Indeed it does.
> It's a bit obtuse though having to wrap my function up in an outer
> template just to scope the template arg correctly.
>
> Do you think it's reasonable that an attribute should be scoped such that
> it can see the template args of the declaration it's bound to?
> It kinda makes sense, an attribute is intrinsically connected to the
> declaration, so it should be able to access any template args given...
>
>
> On 28 May 2013 23:51, Kenji Hara <k.hara.pg at gmail.com> wrote:
>
>> 2013/5/28 Manu <turkeyman at gmail.com>
>>
>>> So I've run into an expression I need to be able to implement std.simd
>>> properly for GDC/LDC.
>>>
>>> Doesn't work:
>>>   @attribute("target", T) void func(string T)(...);
>>>
>>> In this case, currently, the UDA can't receive the template arg that was
>>> given to the function.
>>>
>>> I require that attributes on templates be able to make use of the
>>> template args, since the template arg given may affect the attribute in
>>> some circumstances.
>>>
>>
>> This code works.
>>
>> string attribute(string, string s) { return s; }
>>
>> //@attribute("target", T) void func(string T)() {}
>> template func(string T)
>> {
>>     @attribute("target", T) void func() {}
>> }
>>
>> void main()
>> {
>>     alias f1 = func!"a";
>>     alias f2 = func!"b";
>>     pragma(msg, __traits(getAttributes, f1));   // "a"
>>     pragma(msg, __traits(getAttributes, f2));   // "b"
>>     f1();
>>     f2();
>> }
>>
>> Kenji Hara
>>
>
>
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