On Sunday, 2 October 2016 at 11:37:34 UTC, Manu wrote:
[...]
Why? I have a UI system with modules for each node type. UI
internal stuff is naturally 'package'. Virtuals are perfectly
reasonable within a package.
One reason I can think of: what happens if someone outside the
package extends one of your classes?
===================================
module packA.something;
class Base
{
abstract void foo();
}
module packB.something;
class Derived1: Base
{
override void foo() {} // Oops... should not know about
this method,
// but without it the
class is abstract.
}
===================================
The fact is, package virtual is fine as long as the class cannot
be extended outside the package, or can be extended outside the
package but no subclass defined in this way may need a different
definition of the method. Such a constraint is difficult to
enforce in the language.
