opCast for classes

[Timon Gehr]

On 03/13/2013 12:41 PM, deadalnix wrote:
> On Tuesday, 12 March 2013 at 20:17:33 UTC, Ali Çehreli wrote:
>> ...
>> So, apparently implicit conversion considers the class variable and
>> explicit conversion considers the class object. And this produces a
>> compilation error:
>>
>>     B bnull;
>>     assert(cast(bool)bnull);
>>
>> Error: null dereference in function _D6deneme19__unittestL123991_1FZv
>>
>> Ali
>
> bool toto = bfalse; // Error: cannot implicitly convert expression
> (bfalse) of type module.B to bool
>
> So it isn't the implicit cast kickin here, but a 3rd behavior. The kind
> of behavior that makes D so special and create theses edges cases we all
> love !

It's an unnecessary special case. assert(objRef); checks whether the 
object reference is not null and then it checks the object invariant. 
Walter thinks this is useful.