endless loop with ref and non-ref parameter

[Jonathan M Davis]

On Friday, January 25, 2013 05:14:45 Era Scarecrow wrote:
> On Friday, 25 January 2013 at 01:57:02 UTC, Jonathan M Davis
> 
> wrote:
> > The compiler _has_ to pick either const or ref as having higher
> > precedence. ref was almost certainly chosen as having higher
> > precedence because it avoids a conversion, but also by picking
> > ref, you end up with fewer unnecessary copies, making it the
> > more efficient choice. So, from the standpoint of both type
> > conversions and efficiency, it makes more sense for ref to have
> > precedence over const than the other way around.
> > 
> > The reality of the matter is that regardless of whether const
> > or ref had precedence, you'd still need all 4 overloads or
> > you'd have problems. auto ref and inout can help reduce the
> > number of overloads required, but the function needs to accept
> > all of the type combinations in order to avoid having to
> > convert the type or make unnecessary copies.
> 
>   Personally that doesn't seem like it makes sense. I know it does
> logically, but at the same time it seems silly. If you have
> something as const, why do you need a non-const version?

With templated code, it can be important. But then again, if there's no point 
in having a non-const overload, you can simply not declare any overloads 
without const. You only run into problems when you mix const and non-const.

The compiler has to be able to deal with various combinations of const and ref 
regardless of what it actually makes sense to declare. The only way that I can 
think of to get rid of that problem is to make it illegal to declare both 
const and non-const overloads at the same time, which seems unnecessarily 
restrictive (especially with regards to generic code), even if it doesn't 
normally make sense to overload on const.

- Jonathan M Davis