[:] as empty associative array literal, plus warning for null

[bearophile]

> produces a call to __d_arrayliteralTX, for reasons unknown to 
> me:
>
>
> _D4temp10emptyArrayFZAi comdat
> L0:     push    EAX
>         mov EAX,offset FLAT:_D11TypeInfo_Ai6__initZ
>         push    0
>         push    EAX
>         call    near ptr __d_arrayliteralTX
>         mov EDX,EAX
>         add ESP,8
>         pop ECX
>         xor EAX,EAX
>         ret

Sorry, my mistake, I meant:

__Dmain comdat
L0:     push    EAX
         mov EAX,offset FLAT:_D11TypeInfo_Ai6__initZ
         push    0
         push    EAX
         call    near ptr __d_arrayliteralTX
         add ESP,8
         xor EAX,EAX
         pop ECX
         ret

Bye,
bearophile