why can't structs implement interfaces?

[Lars T. Kyllingstad]

Don wrote:
> bearophile wrote:
>> Bill Baxter:
>>
>>> The good thing is that since most of the machinery is there, the
>>> actual compiler changes required would mostly be just rewrites of new
>>> syntax in terms of existing functionality.
>>
>> I agree, this looks like something that can be added to D even after 
>> D2 comes out of alpha.
>> But Andrei warns us that here it's easy to overdo the design. So I 
>> think that keeping usability low (= keeping things handmade and 
>> low-tech) can be better than a Byzantine and limited design.
>>
>>
>>> In particular there's not a good way for the compiler to give good
>>> error messages about why a concept is not satisfied by a particular
>>> type.
>>
>> Time ago I have asked for a "small" compiler feature: when a 
>> function/class template creates a compile-time error (because some of 
>> the code inside it is not compatible with the specific type given to 
>> the template) I'd like the D compiler to act as GCC, telling me not 
>> just where there is the error inside the template, but also and 
>> *before* that error message to show me the line of where the template 
>> is instantiated. This is another small feature that can be added after 
>> D2 "finalization".
> 
> That's been requested many times. I posted a patch to Walter to do 
> exactly that. It was beautiful. It detected recursive template 
> expansions, and gave really nice error messages. Silently rejected.
> Sigh.


What's the bugzilla number? Should be upvoted.

-Lars