Helping with __mutable (which will be renamed to __metadata)

[Suleyman]

On Monday, 15 April 2019 at 15:59:35 UTC, Timon Gehr wrote:
> At that point, why do you need to slap `immutable` on your type 
> in the first place? Why does your proposed semantics make any 
> sense for reference counting or caching/lazy evaluation?

I don't know but immutability has been breached for sure and 
hiding that with @system doesn't help I would say disallowing 
__mutable inside immutable objects makes more sense than just 
concealing the crime with @system unless someone has a safe 
solution.