hasDataMember and mixin inconsistency

[Olivier Grant]

On Sunday, 27 January 2013 at 16:51:26 UTC, Philippe Sigaud wrote:
>>> string hasDataMember( T )(string M )
>>> {
>>>     return " __traits(compiles, {
>>>         Test t;
>>>         auto _ = t.D; // reading t.M
>>>         t." ~ M ~ " = t." ~ M ~ "; // assign to t.M
>>>     })";
>>> }
>>
>>
>> What is the purpose of "auto _ = t.D;" ?
>
> Just testing whether t.M can be assigned to something (ie, is 
> it a value?)
> I use '_' as a variable name to indicate I don't care for it's 
> precise
> name/value. It's just a placeholder.

Ok, I must be missing something, why "t.D" or is this just a 
typo? And secondly wouldn't "x.M = y.M" take care of checking 
that the member can be read and written to ? Also, doesn't your 
solution require T to be default constructible ?

>> Using dmd 2.060 and command line "rdmd test.d", I get an 
>> assertion fail on
>> both calls that check for a member "init" whether for int or 
>> Test.
>
> Using 2.061 here.

Well that was the problem! I was still using 2.060 which seems to 
have the bug. Now that I've moved to 2.061 everything works as 
expected (your implementation and mine).

Thanks,

Olivier.