Proxy addition

[Dan]

On Thursday, 25 October 2012 at 16:39:57 UTC, Dan wrote:
> From bug tracker I see that Proxy has a few issues, so this has 
> likely been seen. But what would cause this error?
>
> tmp/c.d(16): Error: overloads pure nothrow @safe double(auto 
> ref CcRate b) and pure nothrow @safe double(auto ref CcRate b) 
> both match argument list for opBinary
>
> The error refers to two methods with the same signature. In 
> typecons there are only two "Binary" methods, opBinary and 
> opBinaryRight, both in Proxy, so where is the 
> duplication/conflict coming from?
>
> Thanks
> Dan
> ---------------
> import std.stdio;
> import std.typecons;
> import std.algorithm;
>
> struct CcRate {
>   private double rate = 0;
>   mixin Proxy!rate;
>
>   this(double rate) {
>     this.rate = rate;
>   }
> }
>
> unittest {
>     CcRate r1 = 0.033, r2 = 0.002;
>     writeln(r1+r2);  // compile error
> }
> ---------------

Still trying to understand this. I found that if I change the 
following in Proxy it this example (r1 + r2) works fine. Plus the 
unit tests that are there still work. But, honestly I don't 
understand why...yet.

Thanks,
Dan

----- From typecons.Proxy -----
     auto ref opBinary     (string op, this X, B)(auto ref B b) { 
return mixin("a "~op~" b"); }
----- To -----
     auto ref opBinary     (string op, this X, B)(auto ref B b) 
if(!is(X == B)) { return mixin("a "~op~" b"); }
-----