opDispatch and operator overloads

[Timon Gehr]

On 05/20/2013 05:15 PM, John Colvin wrote:
> struct S {
>      auto opDispatch(string s)(A i){}
> }
>
> struct A {}
>
> void main() {
>      S s;
>      A a;
>      s + a; //Error: incompatible types for ((s) + (a)): 'S' and 'A'
> }
>
> It would be really nice if opDispatch could catch missing operator
> overloads.
>

Agreed. DMD arbitrarily refuses a combination of language features. I 
think it is a compiler bug.

> Also, would it be a good idea to have free functions of all the
> operators (opOpAssign etc...) for builtin types somewhere?

I think built-in members are a better choice than free functions, as the 
operators are built-in. (Also, note that operator overloading is 
implemented in DMD in such a way that it is incompatible with UFCS, 
which does not match the language specification either).

> It's occasionally useful in generic wrappers.

Yes. Maybe you could file a bug report against the opDispatch part and 
an enhancement request for the built-in members part.

http://d.puremagic.com/issues/