Fully transitive const is not necessary

[Janice Caron]

On 01/04/2008, Steven Schveighoffer <schveiguy at yahoo.com> wrote:
>  Second, I'll show how logical const is ALREADY available with D's const,
>  just in a less convenient form.  Let's look at an invariant property that is
>  not invariant:
>
>  class X
>  {
>    private static int _x;
>    invariant int x()
>    {
>        return _x++;
>    }
>  }

That does not break transitivity. You have misunderstood.

"invariant int x()" declares x() to be a function, within whose body
the variable "this" is invariant. X._x is a global variable, unrelated
to "this". Transitivity is not compromised.


>  Notice that despite all efforts of the compiler to make sure invariant is
>  transitive, it still cannot do any parallelizations or optimizations on the
>  call to x.  If it does not have the source code for x, it cannot be sure
>  that x isn't doing something like the above.

However, in the future, you will be able to declare

    class X
    {
        private static int _x;
        invariant int x()
        {
            return _x++; /*ERROR*/
       }
   }

and suddenly - bingo - the offending line will not compile.

You gotta think ahead.