What is the Status of __mutable ?

[Steven Schveighoffer]

On 12/20/18 10:10 AM, Kagamin wrote:
> How about this?
> 
> struct __mutable(T)
> {
>      private size_t _ref;
>      this(T val){ _ref=cast(size_t)val; }
>      T unwrap() const
>      {
>          return cast(T)_ref;
>      }
> }
> 
> struct A
> {
>      __mutable!(int*) rc;
>      this(int) immutable
>      {
>          rc=new int;
>      }
>      int inc() immutable
>      {
>          return ++*rc.unwrap;
>      }
> }
> 
> int main()
> {
>      immutable A b=0;
>      assert(b.inc==1);
>      assert(b.inc==2);
>      return 0;
> }
> 
> I think it doesn't violate type system (formally): the mutable location 
> is never seen as immutable, so immutability is not casted away, but it's 
> not rebindable.

The biggest issue is that immutable is implicitly shared.

-Steve