Revised RFC on range design for D2

[Andrei Alexandrescu]

Michel Fortin wrote:
> On 2008-09-29 23:12:44 -0400, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> said:
> 
>> Indeed, whether or not something can be used as a property will depend 
>> on the qualifiers in vigor.
> 
> And I think this is why binding the availability of the proprety syntax 
> of the setter to the existance and visibility of a getter is not a good 
> idea.
> 
> Basically, doing this makes the "()" syntax safer, and the "=" version 
> more fragile, as the later could become non-functionnal in all kinds of 
> situations where the getter becomes unavailable (removal, deprecation, 
> change in protection, change in constness of the parent, etc.). It means 
> that if I remove or change the visibility of a getter in a program 
> (because it has been found to be erroneous, dangerous, and/or badly 
> used), I will have to change all the calls to the corresponding setter 
> to use the parenthesis form.
> 
> This can be a nuisance while refactoring. It also means that I can't 
> just remove the getter and attempt to recompile to check if it's called 
> somewhere without inducing compilation errors where the setter is used. 
> And I'm sure it'll encourage some silly ones who want to write 
> write-only properties to add a dummy getter that throws an exception, 
> disregarding static checking. I can already see some people recommanding 
> always using the parenthesis syntax when calling setters because then 
> you know you won't have to change it later when you refactor your code; 
> I know I would consider it if I got biten by this, after all we're 
> already doing this in other languages and it's not that painfull.

I think the argument is overstated and a corner case is overblown, but I 
agree there is an issue.

> So I think this idea brings unnecessary coupling between functions, with 
> more drawbacks than benefits. Don't mistake me, I liked your idea at 
> first, especially because I'm not fond of adding a new syntax just for 
> diallowing another, but now I realise don't like its implications of the 
> implicit coupling of the setter with the getter.
> 
> I believe explicit coupling would be better, and that probably means an 
> explicit property syntax as others have requested. But then again, I 
> don't mind much if things stay like they are.
> 
> - - -
> 
> Another funny example:
> 
> module a;
> void func(int a);
> 
> module b;
> int func();
> 
> module c;
> import a;
> import b;
> void main()
> {
>     func(func); // compiles... so
>     func = 5; // compiles too!
> }
> 

The coupling part I agree with, it's unfortunate. Well I guess I'll just 
drop the matter.


Andrei