static interface

[Andrei Alexandrescu]

grauzone wrote:
> Andrei Alexandrescu wrote:
>> grauzone wrote:
>>> Leandro Lucarella wrote:
>>>> Why not? ;)
>>>
>>> The actual question is if Andrei/Walter are interested at all in 
>>> this. Because they didn't show any interest so far. D will probably 
>>> be doomed to compile time bug-typing I mean duck-typing forever.
>>
>> There's an embarrassment of riches when it comes to finding stuff to 
>> work on for D2. I think we need to resign ourselves to the idea that 
>> we need to focus only on one subset of the stream of good ideas that 
>> are being proposed.
> 
> That's understandable of course.
> 
>> FWIW I was keen on structs interacting in interesting ways with 
>> interfaces (and submitted a number of enhancements in that directions) 
>> but then realized there are a number of problems that 
>> structs/interfaces cannot solve. I believe that a better path to 
>> pursue in checking interface conformance is via reflection.
> 
> That's a possible solution (and an easy way out to get rid of language 
> design problems), but I'm sure it's not the best solution. (It also 
> should be a little bit extended to give the user better error messages.) 
> I hope cleaner solutions will be considered later, possibly after D2 is 
> done.
> 
> Which are the problems you mentioned?

I knew this was going to be asked. One issue I remember was that it's 
difficult to talk about "a struct must define a type with certain 
properties". You will say "but you can express that type as another 
interface" but that solves the problem by increasing the size of the 
feature. It gets even more complicated when you want to say "defines a 
type with these or these other properties, depending on the properties 
of this type parameter." I think that all can be solved through 
something that is very similar to C++ concepts, and I would want to 
avoid going that route.

Andrei