invariant/const class storage class

[Andrei Alexandrescu]

Yigal Chripun wrote:
> Walter Bright wrote:
>> Simen Kjaeraas wrote:
>>> Is this really correct behavior? How then are we supposed to
>>> initialize our
>>> invariant objects?
>> Currently, create them as mutable ones, then cast them to invariant.
> 
> I understand casting as breaking the type system. shouldn't there be a
> way to create invariant objects without the cast?
> an invariant constructor seems a good way to solve this. any plans on
> adding such a feature to D2?

There are plans.

> I think it can work like this:
> 
> class A {
>   this(params) {}   // [1]
>   invariant this(params) {}  // [2]
> }
> 
> // create a mutable object - will use type [1] c-tors.
> auto a = new A(params);
> 
> // create an invariant object - will use type [2] c-tors.
> invariant a = new A(params);
> 
> // create a const object - will use type [1] or [2] c-tors.
> const a = new A(params);
> 
> in the const case, if there are two c-tors which only differ by
> invariant-ness of the c-tor using either will create ambiguity and
> therefore should be a compile-time error.

Way, way, way more complicated than this.

Andrei