string types: const(char)[] and cstring

[Chris Nicholson-Sauls]

Walter Bright wrote:
> Reiner Pope wrote:
>> Will there be something in the type system which enables you to safely 
>> say, "This is the only reference to this data, so it's ok for me to 
>> make this invariant" ?
> 
> Safely? No. You will be able to explicitly cast to invariant, however, 
> the programmer will have to ensure it is safe to do so.
> 
>> Does 'scope' happen to have anything to do with that?
> 
> No. Scope just ensures that the reference does not 'escape' the scope 
> it's in.
> 
>> invariant(char)[] createJunk()
>> {
>>     /* scope? */ char[] val = "aaaaa".dup;
>>     size_t index = rand() % 5;
>>     val[index] = rand();
>>
>>     return cast(invariant(char)[]) val;
>> }
>>
>> I mean, do I really need to cast it to invariant there? It's easy to 
>> see that there's only one copy of val's data in existance.
> 
> Easy for you to see, not so easy for the compiler to. And besides:
> 
>     return cast(invariant)val;
> 
> will do the trick more conveniently.

That's an interesting syntax, casting to a trait/attribute with the rest of the type 
inferred.  I presume cast(const) works as well.  (Maybe cast(scope)?  Then again, what's 
the use...)  Given cast(*) where * is invariant/const, is cast(*)T[] the same as 
cast(*(T)[]) or cast(*(T[]))?  That is, does the trait apply to the element type, or the 
array?

-- Chris Nicholson-Sauls