My two cents

[Walter Bright]

On 10/25/2017 12:39 AM, Satoshi wrote:
> Thanks, but I see there 3 problems:
> 1. this example enforce users to use composition instead of inheritance when 
> they wants to create custom descendant.

I don't see an issue with that.

> 2. multiple dispatch levels. Extending the ExtendView in another lib we get 
> triple dispatch for each method.

That's only if you want to hide the interface base class implementation, and 
only if you want to *also* call the base function. There's single dispatch if 
overriding, or not overriding, the base function. You can also inherit directly 
from LibraryView, and there'd be only one dispatch.