Voldemort Types in D

[Adam Wilson]

On Wed, 09 May 2012 10:19:08 -0700, Jonathan M Davis <jmdavisProg at gmx.com>  
wrote:

> On Wednesday, May 09, 2012 10:05:36 Adam Wilson wrote:
>> On Wed, 09 May 2012 08:58:56 -0700, Nicolas Sicard <dransic at gmail.com>
>>
>> wrote:
>> > On Wednesday, 9 May 2012 at 14:30:33 UTC, Andrei Alexandrescu wrote:
>> >>  
>> http://www.reddit.com/r/programming/comments/telhj/voldemort_types_in_d/
>> >>
>> >> Andrei
>> >
>> > One drawback of Voldemort types, is that they are incompatible with  
>> the
>> > generation of .di files (option -H).
>> >
>> > See http://d.puremagic.com/issues/show_bug.cgi?id=5461.
>> >
>> > Nicolas
>>
>> This pull fixes this problem and a bunch of others:
>> https://github.com/D-Programming-Language/dmd/pull/928. However, it
>> currently fails to build on Linux and fails the unittests on Windows
>> thanks to a problem with the dur template function in std.datetime. The
>> solution used by this pull is to include the function body of the
>> auto-function as that was needed to allow Phobos to build correctly  
>> using
>> the DRT DI files. This is the only workable solution as DMD does not  
>> know
>> the type of an auto-function when DI files are generated. No semantic
>> analysis has been performed and since semantic analysis could change the
>> layout of a module you wouldn't want it to be
>> performed.
>
> Actually, dur is in core.time (which is publicly imported by  
> std.datetime),
> but regardless, what's wrong with it? It's incredibly straightforward.
>
> - Jonathan M Davis

All of this is a result of using the above mentioned 928 pull.

This from core.time.d:
Duration dur(string units)(long length) @safe pure nothrow
     if(units == "weeks" ||
        units == "days" ||
        units == "hours" ||
        units == "minutes" ||
        units == "seconds" ||
        units == "msecs" ||
        units == "usecs" ||
        units == "hnsecs" ||
        units == "nsecs")
{
     return Duration(convert!(units, "hnsecs")(length));
}

Gets translated to this in core.time.di:
template dur(string units) if (units == "weeks" || units == "days" ||  
units == "hours" || units == "minutes" || units == "seconds" || units ==  
"msecs" || units == "usecs" || units == "hnsecs" || units == "nsecs")
{
     pure nothrow @safe Duration dur(long length)
     {
         return Duration(convert!(units,"hnsecs")(length));
     }
}

Which results in this error from DMD (HEAD):
../druntime/import/core/time.di(218): Error: this cannot be interpreted at  
compile time, because it has no available source code
std/net/curl.d(187):        called from here: dur(2L)
make[1]: *** [generated/linux/release/32/libphobos2.a] Error 1
make: *** [release] Error 2

But DMD, there *IS* source code to read! Even if it is just a function  
call...

Note the above D->DI translation is the same without the patch, I checked  
on a vanilla DMD 2.059 install. Also, I don't know near enough about  
core.time to begin to guess what D is whining about here... It all looks  
good to me.

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/