 	/// - returns: A signal producer that applies signal's operator to every
 	///            created signal.
 	public func lift<U, F>(_ transform: @escaping (Signal<Value, Error>) -> Signal<U, F>) -> SignalProducer<U, F> {
-		return SignalProducer<U, F>(.makeSignalCore {
+		return SignalProducer<U, F>(SignalCore {
 			// Transform the `Signal`, and pass through the `didCreate` side effect and
 			// the interruptHandle.
 			let instance = self.core.make()

		disposed: (() -> Void)? = nil,
		value: ((Value) -> Void)? = nil
	) -> SignalProducer<Value, Error> {
		return SignalProducer(.makeSignalCore {
			let instance = self.core.make()
			let signal = instance.signal.on(event: event,
			                                failed: failed,


	private func lift<U, F, V, G>(leftFirst: Bool, _ transform: @escaping (Signal<Value, Error>) -> (Signal<U, F>) -> Signal<V, G>) -> (SignalProducer<U, F>) -> SignalProducer<V, G> {
		return { otherProducer in
			return SignalProducer<V, G>(SignalCore {
				let left = self.core.make()
				let right = otherProducer.core.make()

