shared - i need it to be useful

[Steven Schveighoffer]

On 10/18/18 9:35 AM, Steven Schveighoffer wrote:
> 
> struct NotThreadsafe
> {
>    private int x;
>    void local()
>    {
>      ++x; // <- invalidates the method below, you violate the other
> function's `shared` promise
>    }
>    void notThreadsafe() shared
>    {
>      atomicIncrement(&x);
>    }
> }
> 

[snip]

> But on top of that, if I can't implicitly cast mutable to shared, then 
> this ACTUALLY IS thread safe, as long as all the casting in the module 
> is sound (easy to search and verify), and hopefully all the casting is 
> encapsulated in primitives like you have written. Because someone on the 
> outside would have to cast a mutable item into a shared item, and this 
> puts the responsibility on them to make sure it works.
> 

Another thing to point out -- I can make x public (not private), and 
it's STILL THREAD SAFE.

-Steve