Implementing SmartPtr - compiler bug?

[Szymon Gatner via Digitalmars-d-learn]

On Monday, 27 October 2014 at 14:04:53 UTC, Marc Schütz wrote:
> On Monday, 27 October 2014 at 12:40:17 UTC, Shachar Shemesh 
> wrote:
>> On 27/10/14 11:31, Szymon Gatner wrote:
>>
>>> Right, sorry. Tho I admit I made assumptions since that was 
>>> not the full
>>> code.
>>
>> I've opened a bug. It has a fully contained sample (that does 
>> not, in fact, implement smartptr).
>>
>> https://issues.dlang.org/show_bug.cgi?id=13661
>
> Strictly speaking, your opAssign is wrong, because it doesn't 
> swap source and destination, as it should. This doesn't matter 
> here, but it would for a smartptr.
>
> However, that opAssign isn't even called is certainly a bug.

Why would opAssign() swap things?