change 'this' pointer for structs to reference type

[Robert Fraser]

Andrei Alexandrescu wrote:
> Robert Fraser wrote:
>> Walter Bright wrote:
>>> Andrei suggested this change, and I think it is a great idea. D ought 
>>> to be moving away from pointers for routine work, and this would make 
>>> a lot of sense.
>>>
>>> It would entail some changes to user code, mostly when dealing with 
>>> the opCmp and opEquals member functions. The function signatures for 
>>> them would be changed to opCmp(ref const S).
>>
>> While we're at it, let's have "in" return a reference instead of a 
>> pointer for AAs.
> 
> Unfortunately that won't be possible because references can't be null.
> 
> Andrei

Ah, I see. But then what about the "no pointers in SafeD" thing... does 
this mean SafeD will also lack the "in" operator?