[swift-evolution] Specify type of a delegate which conforms to a protocol

[Craig Cruden]

> On 2016-02-11, at 20:38:21, Ross O'Brien via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I think this proposal should stick to the intersection type: a type which inherits from at most one class (multiple inheritance should definitely be a separate proposal) if it conforms to all of one or more specified protocols.
> 
> The next issue I'd see with the union type is that it's the already proposed Either type.
> 
> — Ross

Actually, no the union type has not been proposed.  It has been slightly talked about in the Either type discussion.  Either was a simple implementation that could do 80% of the use cases of type unions would allow (with 1% of the work :p).  

Whereas, union and intersection types are basically making changes to the type system itself — is it not?