On Wed, 05 Jun 2013 18:32:58 -0400, Adam D. Ruppe
<[email protected]> wrote:
On Wednesday, 5 June 2013 at 22:03:05 UTC, Walter Bright wrote:
1. Introduce 'virtual' storage class. 'virtual' not only means a method
is virtual, but it is an *introducing* virtual, i.e. it starts a new
vtbl[] entry even if there's a virtual of the same name in the base
classes. This means that functions marked 'virtual' do not override
functions marked 'virtual'.
Your upgrade path sounds generally good to me, I can live with that.
But I want to clearify this #1:
class A { virtual void foo(); }
class B : A { virtual void foo(); }
Error, yes? It should be "override void foo();" or "override final void
foo();".
(override and virtual together would always be an error, correct?)
Whereas:
class A { virtual void foo(); }
class B : A { virtual void foo(int); }
is OK because foo(int) is a new overload, right?
No, I think it introduces a new foo. Calling A.foo does not call B.foo.
In other words, it hides the original implementation, there are two vtable
entries for foo.
At least, that is how I understood the C# description from that post, and
it seems Walter is trying to specify that. The idea is that B probably
defined foo before A did, and A adding foo should not break B, B didn't
even know about A's foo.
-Steve
