Objective C protocols

[John Colvin]

On Saturday, 16 May 2020 at 19:14:51 UTC, John Colvin wrote:
> What's the best way to implement an Objective C protocol in D?
>
> I see mention here 
> https://dlang.org/changelog/2.085.0.html#4_deprecated_objc_interfaces but it's not clear where things are these days.

Based on some experimentation, I'm starting to wonder do 
protocols actually have any runtime component in Objective C? 
Because if I pass in an extern(Objective-C) class with the right 
interface to a function expecting a protocol everything just 
works.