On Thu, 06 Jun 2013 11:40:18 -0400, Joseph Rushton Wakeling
<joseph.wakel...@webdrake.net> wrote:
On 06/06/2013 05:00 PM, Steven Schveighoffer wrote:
On Wed, 05 Jun 2013 21:14:08 -0400, Jonathan M Davis
<jmdavisp...@gmx.com> wrote:
I would have expected something more like
1. 'virtual' means a method is an "introducing" one.
2. 'override' means override with a non-final function.
3. 'final override' means a method overrides a base virtual function
with a
final function.
4. 'final' by itself both mean final and non-overriding.
I agree, I think it can be expressed by answering two questions:
1. Do you want to participate in a base class' virtual call
2. Do you want to allow derived classes to participate in the virtual
call.
If you answer yes to 1, add override, otherwise (or if there is no base
method),
add nothing (in C# answering no, you should add 'new' if there is an
existing
base function)
If you answer yes to 2, add virtual, otherwise, add final.
I see a potential problem with allowing 'final' on its own to mean
'final and
non-overriding', which is that if you _mean_ to override a function in
the base
class, but put simply 'final' and not 'override', it will still be
accepted by
the compiler -- and it may not be obvious that the override is not
taking place.
Yes, this is a departure from the current code, which doesn't allow this.
But it is a generalized problem, not specific to final. It's basically
the lack of a storage class for meaning "no, I don't want to override the
function". Note that final does NOT do this. In fact, we don't have a
way to do this now.
new could be that storage class, but I am cautious about it. new has a
position close to that context, for custom allocators.
Another storage class would complete the solution, and make intentions
very easy to make obvious. At that point, we could have a warning/error
for under-specification.
And another note to make is that the case where you are 'hiding' a base
final function isn't really a problem. It's more when you are hiding a
virtual function, that this becomes an issue. More likely, when you are
hiding a *new* virtual function, because it didn't exist when you wrote
your code.
-Steve
