struct EnumToFlags(alias E) {
	template opDispatch(string Name) {
		enum opDispatch = 1 << __traits(getMember, E, Name);
	};
};


enum X
{
a,b,c
}

auto q = EnumtoFlags!X;


auto m = q.a;

with(q)
{
   auto m = a;
}

a undefined.

Any way to get it to work? Maybe a full blowing string mixin is needed to generate the flag enum?

This is fairly complex thing, but I managed to get it working:

template EnumToFlags(E) if(is(E == enum))
{
    import std.traits, std.typecons, std.string;

    private static auto implementation()
    {
        string result;
        foreach(i, enumMem; EnumMembers!E)
        {
            result ~= format("enum %s = 1 << %s;\n", enumMem, i);
        }
        return result;
    }

    mixin(implementation);
};

enum X
{
    a,b,c
}

void main()
{
    alias q = EnumToFlags!X;

    with(q)
    {
       auto m = a;
    }
}

It may well be that with(x) only looks for x members, it probably does not try to look for templates. If so, opDispatch does not do the trick here. But the above does.

On Friday, 20 January 2017 at 09:12:04 UTC, Dukc wrote:
> template EnumToFlags(E) if(is(E == enum))
> {
>     import std.traits, std.typecons, std.string;
>
>     //...
> }

I think that typecons import was needless, you could try removing it...

On Friday, 20 January 2017 at 09:12:04 UTC, Dukc wrote:
> This is fairly complex thing, but I managed to get it working:
>
> template EnumToFlags(E) if(is(E == enum))
> {
>     import std.traits, std.typecons, std.string;
>
>     private static auto implementation()
>     {
>         string result;
>         foreach(i, enumMem; EnumMembers!E)
>         {
>             result ~= format("enum %s = 1 << %s;\n", enumMem, i);
>         }
>         return result;
>     }
>
>     mixin(implementation);
> };
>
> enum X
> {
>     a,b,c
> }
>
> void main()
> {
>     alias q = EnumToFlags!X;
>
>     with(q)
>     {
>        auto m = a;
>     }
> }
>
> It may well be that with(x) only looks for x members, it probably does not try to look for templates. If so, opDispatch does not do the trick here. But the above does.

Thanks.

That is basically what I was thinking and it does work.