User Defined Attributes

[dennis luehring]

Am 06.11.2012 17:50, schrieb Walter Bright:
> On 11/6/2012 8:42 AM, dennis luehring wrote:
>> Am 06.11.2012 16:18, schrieb Walter Bright:> On 11/6/2012 6:30 AM, dennis
>> luehring wrote:
>>  >   > Am 06.11.2012 14:14, schrieb Adam D. Ruppe:
>>  >   >> On Tuesday, 6 November 2012 at 07:55:51 UTC, Walter Bright wrote:
>>  >   >>> User Defined Attributes (UDA) are compile time expressions that
>>  >   >>> can be attached to a declaration.
>>  >   >>
>>  >   >> Hmmm, it didn't work on the most important place for my use case,
>>  >   >> function parameters:
>>  >   >>
>>  >   >> void a(["test"] int foo) {
>>  >   >>       pragma(msg, __traits(getAttributes, foo));
>>  >   >> }
>>  >   >
>>  >   > sad - but its still very young feature :)
>>  >   >
>>  >   > im using something like an description on my methods to describe parameter
>>  >   > "features" for an resource manager - something like "read", "write", "copy",
>>  >   > "read_write" etc.
>>  > But there's already out=write, read=all of them, read_write=ref, copy=not a ref
>>  > or an out.
>>
>> and now expand that to an higher level manager that use such information for
>> implementing(generating) runtime loading and locking strategies in a tree/graph
>> based environment - based on the parameters needs ... i've got something like
>> that in C++ using its own interface description language and an generator
>
> But D already has parameter attributes that cover those bases. What would UDAs
> add to that? (I know C++ is deficient in this, which is why IDL was invented,
> but I don't see what UDAs add to what D already provides - no IDL is needed for D).
>

just 2 questions:

1. what if my needs are beyond D?

for example my idl allows me to define a type based query source for 
parameters

CalculateStuff( TypeX [source="\\placement\(typeA|typeB|typeC)"] my_usage )

this defines the source of assignable objects to this method

2. what is the reason for stopping right before parameters? (except less 
coding on your side)