Extra .tupleof field in structs with disabled postblit blocks non-GC-allocation trait

[Per Nordlöw]

On Wednesday, 9 May 2018 at 14:36:38 UTC, Per Nordlöw wrote:
> On Wednesday, 9 May 2018 at 14:34:02 UTC, Per Nordlöw wrote:
>> On Wednesday, 9 May 2018 at 14:20:41 UTC, Per Nordlöw wrote:
>>> If so, we can temporarily modify the trait to exclude the 
>>> last `void*` member of the `S.tuple`. Given that it's always 
>>> added as the last member.
>>
>> Also note that
>>
>>     pragma(msg, __traits(isDisabled, S.this(this)));
>>
>> fails to compile as
>>
>>     Error: identifier expected following `.`, not `this`
>
> Ahh, but both
>
>     pragma(msg, __traits(isDisabled, S.__postblit));
>     pragma(msg, __traits(isDisabled, S.__xpostblit));
>
> prints true for a struct with `@disable this(this);`
>
> Which one should I pick to check if last element of `S.tupleof` 
> should be discarded?

Managed to put together the hack

private template mustAddGCRangeOfStructOrUnion(T)
if (is(T == struct) ||
     is(T == union))
{
     import std.traits : hasUDA;
     import std.meta : anySatisfy;
     static if (__traits(hasMember, T, "__postblit"))
     {
         static if (__traits(isDisabled, T.__postblit))
         {
             enum mustAddGCRangeOfStructOrUnion = 
anySatisfy!(mustAddGCRangeOfMember, T.tupleof[0 .. $ - 1]);
         }
         else
         {
             enum mustAddGCRangeOfStructOrUnion = 
anySatisfy!(mustAddGCRangeOfMember, T.tupleof);
         }
     }
     else
     {
         enum mustAddGCRangeOfStructOrUnion = 
anySatisfy!(mustAddGCRangeOfMember, T.tupleof);
     }
}

defined here

https://github.com/nordlow/phobos-next/blob/master/src/gc_traits.d#L81

Destroy.