Templates class member functions not conditional?

[bearophile]

monarch_dodra:

> Is this not the case for D? Or is it currently a limitation?

In this case I think D is working as designed. All functions 
inside a template are created when you instantiate it.


> Can I ever expect we'll get a "conditionally compiled on 
> requirement" functionality for template struct member functions.

I have asked for a @templated(Arg1, Arg2, ...) that's usable for 
this purpose too, but Walter has not commented so far.


> struct C(T)
> {
>     private T val;
>     static if(isAssignable(T!T))
>     {
>         @property void front(T value)
>             {val = value;}
>     }
> }

Probably such use of a static if (or debug, version, etc) is the 
idiomatic way to do what you want in D. It's easy to see and 
understand for the person that reads the code.


> struct C(T)
> {
>     private T val;
>     @property void front()(T value)
>         {val = value;}
> }
>
> This works, and is correctly "conditionally compiled on 
> requirement". The signature is kind of kludgy, but it works... 
> AND, if someone *does* attempt to make the call, then a verbose 
> compile error appears.

This doesn't look bad, just remember this doesn't work:


struct C(T) {
     private T val;
     @property void front()(T value) {
         val = value;
     }
}
void main() {
     C!int ci;
     auto f = &ci.front;
     assert(ci.val == 0);
     f(1);
     assert(ci.val == 1);
}

Bye,
bearophile