Helping with __mutable (which will be renamed to __metadata)

[Suleyman]

On Monday, 15 April 2019 at 11:17:55 UTC, Timon Gehr wrote:
> On 14.04.19 22:55, Suleyman wrote:
>> ...
>
> No, the point is that whatever high-level rewrites you can 
> deduce from `immutable` and `pure` shouldn't be restricted by 
> code that modifies `__metadata`.
>
> ...

Just making it @system is not helping much instead of evading 
reality you rather treat as it really is an immutable ref with 
mutable fields hence the compiler must not elide function calls 
with these weakly immutable arguments.