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[Marc Schütz via Digitalmars-d]

On Monday, 16 November 2015 at 02:26:29 UTC, Andrei Alexandrescu 
wrote:
> Yah, I agree with that argument. Probably @mutable is a more 
> principled way to go about things.

Glad to here that. I think the current transitive const system is 
really good and shouldn't be watered down beyond necessity. And a 
@mutable keyword, too, shouldn't just mean "immutability or 
const-ness end here", thus allowing any kind of mutation. What we 
actually need for immutable/const refcounting etc. is 
_non-observable mutation_, i.e. physical mutability, but without 
observable effects outside of the type's implementation (better 
yet, restricted to very short parts of it, just like @trusted).