is my code to get CTFE instantiated object valid D ?

[chmike via Digitalmars-d-learn]

On Saturday, 28 May 2016 at 21:21:34 UTC, ag0aep6g wrote:
> On 05/28/2016 09:54 PM, chmike wrote:
>> The only inconvenience left is that we can't have mutable 
>> references
>> to immutable objects.
>
> There is std.typecons.Rebindable for that.

That would be a good news. What is the right way to use it ? I 
had a hard time to understand how to use Rebindable.

Rebindable!(immutable Category) instance( return 
Rebindable!(immutable Category)(instance_); }

Or should, I do it like that ?

Rebindable!(const Category) instance( return Rebindable!(const 
Category)(instance_); }

The immutable and const concepts are really different from C and 
C++.

A problem with rebindable is that its current assembly 
translation for 'is' test does a byte per byte comparison which 
is much less efficient than a direct 64bit comparison of the 
struct.
I checked that with dmd. I don't know about gdc and ldc. This is 
something that will,be optimized soon I hope.