Collections question

[Jakob Ovrum via Digitalmars-d]

On Saturday, 28 November 2015 at 13:41:10 UTC, Andrei 
Alexandrescu wrote:
> On 11/28/15 2:26 AM, Jakob Ovrum wrote:
>> Another thing: wouldn't providing a custom allocator require a 
>> separate
>> primitive?
>
> All collections will work with IAllocator. -- Andrei

Yes, I assumed as much. So how would this be handled? Is this not 
a relevant question to the construction issue?