Update the transforming Signal.Observer initializer.

Author: andersio

Sources/Observer.swift

@@ -30,13 +30,13 @@ extension Signal {
 		/// - parameters:
 		///   - observer: The observer to transform.
 		///   - transform: The transform.
-		///   - disposable: The disposable to be disposed of when the transformation
-		///                 yields any terminal event that is not originated from the
-		///                 upstream.
+		///   - disposable: The disposable to be disposed of when the `TransformerCore`
+		///                 yields any terminal event. If `observer` is a `Signal` input
+		///                 observer, this can be omitted.
 		internal init<U, E: Swift.Error>(
 			_ observer: Signal<U, E>.Observer,
 			_ transform: @escaping Event.Transformation<U, E>,
-			_ disposable: Disposable
+			_ disposable: Disposable? = nil
 		) {
 			var hasDeliveredTerminalEvent = false
 
@@ -46,7 +46,7 @@ extension Signal {
 
 					if event.isTerminating {
 						hasDeliveredTerminalEvent = true
-						disposable.dispose()
+						disposable?.dispose()
 					}
 				}
 			}

Sources/Signal.swift

@@ -539,7 +539,7 @@ extension Signal {
 	/// - returns: A signal that forwards events yielded by the action.
 	internal func flatMapEvent<U, E>(_ transform: @escaping Event.Transformation<U, E>) -> Signal<U, E> {
 		return Signal<U, E> { observer in
-			return self.observe(.init(observer, transform, NopDisposable.shared))
+			return self.observe(Signal.Observer(observer, transform))
 		}
 	}
 

Sources/SignalProducer.swift

@@ -336,7 +336,7 @@ private final class TransformerCore<Value, Error: Swift.Error, SourceValue, Sour
 	internal override func makeInstance() -> Instance {
 		let product = source.makeInstance()
 		let signal = Signal<Value, Error> { observer in
-			return product.signal.observe(.init(observer, transform, product.interruptHandle))
+			return product.signal.observe(Signal.Observer(observer, transform))
 		}
 
 		return Instance(signal: signal,