Nested generics

[hachinobu]

Hi!

How about using Nested generics released in Swift 3.1?

I want to make State and Observer nested generics.

For example as below.

extension Promise {
	
	/// ....
	internal indirect enum State {
		case pending
		case resolved(_: Value)
		case rejected(_: Error)
		
		/// It continues below....
		
	}
		
	/// ....
	internal indirect enum Observer {
		typealias ResolveObserver = ((Value) -> (Void))
		typealias RejectObserver = ((Error) -> (Void))
		
		case onResolve(_: Context, _: ResolveObserver)
		case onReject(_: Context, _: RejectObserver)
		
		/// It continues below...		
	}
	
}

If there is no problem I think I will give out PR.

[malcommac]

Hi, make a PR, it seems to be a great idea to get a cleaner code. :-)

[malcommac]

Added in 0.9.5. Thanks