constancy and template parameters in D2.009+

[Christopher Wright]

Janice Caron wrote:
> I think the template idea actually works. You could implement it in
> std.typecons as
> 
> template RemoveHeadConst(T) { alias T RemoveHeadConst; }
> 
> It ought to work because the parameter has been expressed as (T), not
> (T:T), or my suggested (init T). If that works, one of the two
> problems is solved without /any/ modification to the language.
> 
> That just leaves (1)...

Of course, if you say that the constness of parameters should always be 
preserved, you'd get:

template RemoveHeadConst(T) {
    static if (is (T : const(U), U)) {
       alias U RemoveHeadConst;
    } else {
       alias T RemoveHeadConst;
    }
}

It's really just a matter of which case will be more common.