What's the deal with "Warning: explicit element-wise assignment..."

[Rene Zwanenburg via Digitalmars-d]

On Wednesday, 16 April 2014 at 06:59:30 UTC, Steve Teale wrote:
> On Tuesday, 15 April 2014 at 16:02:33 UTC, Steven Schveighoffer 
> wrote:
>
>> Sorry, I had this wrong. The [] on the left hand side is 
>> actually part of the []= operator. But on the right hand side, 
>> it simply is a [] operator, not tied to the =. I erroneously 
>> thought the arr[] = ... syntax was special for arrays, but I 
>> forgot that it's simply another operator.
>>
> Steve, where do I find the []= operator in the documentation? 
> It does not seem to be under Expressions like the other 
> operators. Has it just not got there yet?
>
> Steve

It's under op assignment operator overloading:
http://dlang.org/operatoroverloading.html#OpAssign