Iterating over mixin template members

[Hipreme]

So, I've came to a situation where I must use mixin template for 
defining members overloads, like:
```d
mixin template OverloadGen()
{
     static if(hasMethod!(typeof(this), "add", int, int))
     {
         float add(float x, float y){return x+y;}
     }
     static if(hasMethod!(typeof(this), "mul", int, int))
     {
         float mul(float x, float y){return x*y;}
     }
}

```


I know this example is obvious, but I'm using this for a far more 
complex, so I need that to work.

The current way I tried to solve that was using string mixins 
such as:

```d
enum mixOverloadGen()
{
     return q{
         mixin OverloadGen __ogen__;
         static foreach(mem; __traits(allMembers, __ogen__))
         {
             mixin("alias ",mem," = __ogen__.",mem,";");
         }
     };
}

class Tester
{
     int add(int, int){return 0;}
     mixin(mixOverloadGen);
}
```

The problem doing that is that I can have access to `__ogen__`, 
which makes code like that valid: `tester.__ogen__.add`. I can't 
make `private mixin OverloadGen __ogen__`, because I won't be 
able to publicly access my overloads.


And doing `static foreach(mem; mixin OverloadGen)` is also 
invalid, tried with allMembers, so, this is my current solution, 
the other thing I could do is instead of aliasing to the mixin 
members, I could make them private and declare a public function 
inside my string mixin which calls those, which is just wasteful: 
increase compile time, runtime usage and code complexity.