shared - i need it to be useful

[Nicholas Wilson]

On Sunday, 21 October 2018 at 09:58:18 UTC, Walter Bright wrote:
> On 10/20/2018 11:08 AM, Nicholas Wilson wrote:
>> You can if no-one else writes to it, which is the whole point 
>> of Manu's proposal. Perhaps it should be const shared instead 
>> of shared but still.
>
> There is no purpose whatsoever to data that can be neither read 
> nor written.

Indeed but there is a subtle difference between that and Manu's 
proposal: access through the shared variable may not have 
non-atomic reads, not no reads.

> Shared data is only useful if, at some point, it is 
> read/written,

Yes

> presumably by casting it to unshared in @trusted code.

That is one way to do it, others include atomics  and other 
@trusted primitives

> As soon as that is done, you've got a data race with the other 
> existing unshared aliases.

You're in @trusted code, that is the whole point. The onus is on 
the programmer to make that correct, same with regular 
@safe/@trusted at system code.