On Tue, Jul 10, 2012 at 04:58:06PM -0700, Walter Bright wrote:
> On 7/10/2012 4:19 PM, H. S. Teoh wrote:
> >On Tue, Jul 10, 2012 at 04:05:51PM -0700, Walter Bright wrote:
> >>On 7/10/2012 4:05 PM, H. S. Teoh wrote:
[...]
> >Nqt in this case. The const(B) reference does not permit any of B's methods to mutate the members of B -- you cannot downcast a const(B) reference to a C reference. As far as the methods of B are concerned, the object is immutable.
> >
> >The interesting part is when C's methods override B's methods: those methods _can_ mutate the object, but not the members inherited from B.  And this does not break immutability; you cannot cast const(B) to C, so if you start with immutable(B), it will remain immutable no matter what.  You can't call C's methods from the const(B) reference, and you can't override B's methods with C's mutating methods without actually having a mutable C to begin with.
> >
> >
> >T
> >
> 
> If you've found a way to mutate const and have it stay const, then there's a hole in the typing system.

The const in const(B) applies to the B portion of the object. Just because the C portion changes, doesn't violate the const-ness of the B portion.

I know this isn't how the current type system works, but perhaps it can be made to work in a way that makes sense.


T

-- 
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