[D-runtime] Why does druntime us .di files instead of .d?

[Sean Kelly]

On Jul 13, 2011, at 4:01 PM, Jonathan M Davis wrote:

> On 2011-07-13 15:41, Walter Bright wrote:
>> On 7/13/2011 3:19 PM, Jonathan M Davis wrote:
>>> Given its heavy use of templates, I'm not sure how much that'll buy us in
>>> terms of compilation speed, and since it's all open source, I don't know
>>> why it would matter about hiding implementation details.
>> 
>> Consider the garbage collector. Should every compilation have to recompile
>> that, too?
> 
> Since it doesn't take very long to compile, I really don't care much 
> personally, and I think that it's just simpler to only deal with .d files. 
> However, I'm not against the use of .di files if it speeds up compilation and 
> doesn't have any major drawbacks. My primary concern at the moment (and why I 
> brought it up in the first place) is that it seems to be affecting CTFE. For 
> instance, this program
> 
> ====
> import std.stdio;
> import std.string;
> 
> enum a = strip(" hello world");
> 
> void main() {}
> ====
> 
> currently fails to compile, giving these errors:
> 
> ====
> /home/jmdavis/dmd2/linux/bin/../../src/phobos/std/string.d(1468): Error: 
> _aApplycd2 cannot be interpreted at compile time, because it has no available 
> source code

This function is in src/rt, which isn't publicly visible code (much like the GC).  Is there a similar example involving a module in core.*?