Fallback 'catch-all' template functions

[Stefan Koch via Digitalmars-d]

On Thursday, 1 September 2016 at 05:37:50 UTC, Manu wrote:
> So, consider a set of overloads:
>
>   void f(T)(T t) if(isSomething!T) {}
>   void f(T)(T t) if(isSomethingElse!T) {}
>   void f(T)(T t) {}
>
> I have a recurring problem where I need a fallback function 
> like the bottom one, which should be used in lieu of a more 
> precise match. This is obviously an ambiguous call, but this is 
> a pattern that comes up an awful lot. How to do it in D?
>
> I've asked this before, and people say:
>
>   void f(T)(T t) if(!isSomething!T && !isSomethingElse!T) {}
>
> Consider that more overloads are being introduced by users 
> spread out across many modules that define their own kind of T; 
> this solution is no good.

To my knowledge there is currently no clean way of doing this.
The easiest workaround would be to introduce another name for the 
implementation.

then it would look like
void f(T)(T t) {
   static if (is(fImpl(t) == void)) {
     f(t);
   } else {
     // default impl here
   }
}