shared - i need it to be useful

[Steven Schveighoffer]

On 10/17/18 10:18 AM, Timon Gehr wrote:
> On 17.10.2018 15:40, Steven Schveighoffer wrote:
>> On 10/17/18 8:02 AM, Timon Gehr wrote:
>>> Now, if a class has only shared members, that is another story. In 
>>> this case, all references should implicitly convert to shared. 
>>> There's a DIP I meant to write about this. (For all qualifiers, not 
>>> just shared).
>>
>> When you say "shared members", you mean all the data is shared too or 
>> just the methods are shared?
>>
>> If not the data, D has a problem with encapsulation. Not only all the 
>> methods on the class must be shared, but ALL code in the entire module 
>> must be marked as using a shared class instance. Otherwise, other 
>> functions could modify the private data without using the proper synch 
>> mechanisms.
>>
>> We are better off requiring the cast, or enforcing that one must use a 
>> shared object to begin with.
>>
>> I think any sometimes-shared object is in any case going to benefit 
>> from parallel implementations for when the thing is unshared.
>>
>> -Steve
> 
> The specific proposal was that, for example, if a class is defined like 
> this:
> 
> shared class C{
>      // ...
> }
> 
> then shared(C) and C are implicitly convertible to each other. The 
> change is not fully backwards-compatible, because right now, this 
> annotation just makes all members (data and methods) shared, but child 
> classes may introduce unshared members.

OK, so the proposal is that all data and function members are shared. 
That makes sense.

In one sense, because the class reference is conflated with the type 
modifier, having a C that isn't shared, actually have it's class data be 
shared, would be useful.

-Steve