[Dlang-study] [lifetime] Few root decisions to take on RC classes

[Andrei Alexandrescu]

On 11/02/2015 10:38 AM, Martin Nowak wrote:
> On 11/02/2015 01:20 AM, Andrei Alexandrescu wrote:
>> class Widget
>>    static Widget g;
>>    void fun()
>>    {
>>      g = this;
>>    }
>> }
>>
>> If we make the entire Widget reference-counted, the compiler knows how
>> to make the code work. If we go the @noescape route, this code and
>> others like it will be statically disallowed. So we end up with
>> something more restrictive (or more complicated if we decide to allow
>> certain escape patterns).
>
> Why are we trying so hard to make bad code work? Sharing the ownership
> of a class from within a method can be very surprising and can always be
> replaced by sharing with the function (passing as argument)/assigning on
> the callsite.

The example is chosen to be simple, not good or representative. In real 
code shared ownership is both frequent and desirable.

> Even more important the @rc scheme doesn't seem to solve a much more
> common use case.
>
> class Widget
> {
>    void fun()
>    {
>      escapingReferenceToFoo(field);
>    }
>    Foo field;
> }

Is Foo a class type or not?


Andrei