[skip ci] WIP

Sources/Action.swift

@@ -116,7 +116,8 @@ public final class Action<Input, Output, Error: Swift.Error> {
 		let isEnabled = MutableProperty(actionState.value.isEnabled)
 		self.isEnabled = Property(capturing: isEnabled)
 
-		func modifyActionState<Result>(_ action: (inout ActionState<State.Value>) throws -> Result) rethrows -> Result {
+		@Sendable
+		func modifyActionState<Result>(_ action: @Sendable (inout ActionState<State.Value>) throws -> Result) rethrows -> Result {
 			return try actionState.begin { storage in
 				let oldState = storage.value
 				defer {

Sources/Atomic.swift

@@ -14,7 +14,7 @@ import MachO
 /// A simple, generic lock-free finite state machine.
 ///
 /// - warning: `deinitialize` must be called to dispose of the consumed memory.
-internal struct UnsafeAtomicState<State: RawRepresentable> where State.RawValue == Int32 {
+internal struct UnsafeAtomicState<State: RawRepresentable>: Sendable where State.RawValue == Int32 {
 	internal typealias Transition = (expected: State, next: State)
 #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
 	private let value: UnsafeMutablePointer<Int32>
@@ -29,6 +29,7 @@ internal struct UnsafeAtomicState<State: RawRepresentable> where State.RawValue
 	}
 
 	/// Deinitialize the finite state machine.
+	@Sendable
 	internal func deinitialize() {
 		value.deinitialize(count: 1)
 		value.deallocate()
@@ -104,7 +105,8 @@ internal struct UnsafeAtomicState<State: RawRepresentable> where State.RawValue
 
 /// `Lock` exposes `os_unfair_lock` on supported platforms, with pthread mutex as the
 /// fallback.
-internal class Lock: LockProtocol {
+// TODO: unckecked? subclass?
+internal class Lock: LockProtocol, @unchecked Sendable {
 	#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
 	@available(iOS 10.0, *)
 	@available(macOS 10.12, *)
@@ -212,7 +214,7 @@ internal class Lock: LockProtocol {
 	func `try`() -> Bool { fatalError() }
 }
 
-internal protocol LockProtocol {
+internal protocol LockProtocol: Sendable {
 	static func make() -> Self
 
 	func lock()
@@ -229,7 +231,7 @@ internal struct NoLock: LockProtocol {
 }
 
 /// An atomic variable.
-public final class Atomic<Value> {
+public final class Atomic<Value>: @unchecked Sendable {
 	private let lock: Lock
 	private var _value: Value
 

Sources/Bag.swift

@@ -10,7 +10,7 @@
 public struct Bag<Element> {
 	/// A uniquely identifying token for removing a value that was inserted into a
 	/// Bag.
-	public struct Token {
+	public struct Token: Sendable {
 		fileprivate let value: UInt64
 	}
 
@@ -97,3 +97,5 @@ extension Bag: RandomAccessCollection {
 		}
 	}
 }
+
+extension Bag: Sendable where Element: Sendable {}

Sources/Disposable.swift

@@ -8,14 +8,15 @@
 
 /// Represents something that can be “disposed”, usually associated with freeing
 /// resources or canceling work.
-public protocol Disposable: AnyObject {
+public protocol Disposable: AnyObject, Sendable {
 	/// Whether this disposable has been disposed already.
 	var isDisposed: Bool { get }
 
 	/// Disposing of the resources represented by `self`. If `self` has already
 	/// been disposed of, it does nothing.
 	///
 	/// - note: Implementations must issue a memory barrier.
+	@Sendable
 	func dispose()
 }
 
@@ -58,22 +59,22 @@ internal final class _SimpleDisposable: Disposable {
 /// A disposable that has already been disposed.
 internal final class NopDisposable: Disposable {
 	static let shared = NopDisposable()
-	var isDisposed = true
+	let isDisposed = true
 	func dispose() {}
 	private init() {}
 }
 
 /// A type-erased disposable that forwards operations to an underlying disposable.
 public final class AnyDisposable: Disposable {
-	private final class ActionDisposable: Disposable {
+	private final class ActionDisposable: Disposable, @unchecked Sendable {
 		let state: UnsafeAtomicState<DisposableState>
-		var action: (() -> Void)?
+		var action: (@Sendable () -> Void)?
 
 		var isDisposed: Bool {
 			return state.is(.disposed)
 		}
 
-		init(_ action: (() -> Void)?) {
+		init(_ action: (@Sendable () -> Void)?) {
 			self.state = UnsafeAtomicState(.active)
 			self.action = action
 		}
@@ -100,7 +101,7 @@ public final class AnyDisposable: Disposable {
 	///
 	/// - parameters:
 	///   - action: A closure to run when calling `dispose()`.
-	public init(_ action: @escaping () -> Void) {
+	public init(_ action: @escaping @Sendable () -> Void) {
 		base = ActionDisposable(action)
 	}
 
@@ -123,7 +124,7 @@ public final class AnyDisposable: Disposable {
 }
 
 /// A disposable that will dispose of any number of other disposables.
-public final class CompositeDisposable: Disposable {
+public final class CompositeDisposable: Disposable, @unchecked Sendable {
 	private let disposables: Atomic<Bag<Disposable>?>
 	private var state: UnsafeAtomicState<DisposableState>
 
@@ -203,7 +204,7 @@ public final class CompositeDisposable: Disposable {
 	///            composite has been disposed of, `disposable` has been disposed of, or
 	///            `disposable` is `nil`.
 	@discardableResult
-	public func add(_ action: @escaping () -> Void) -> Disposable? {
+	public func add(_ action: @escaping @Sendable () -> Void) -> Disposable? {
 		return add(AnyDisposable(action))
 	}
 
@@ -246,7 +247,7 @@ public final class CompositeDisposable: Disposable {
 	/// - returns: An instance of `DisposableHandle` that can be used to opaquely
 	///            remove the disposable later (if desired).
 	@discardableResult
-	public static func += (lhs: CompositeDisposable, rhs: @escaping () -> Void) -> Disposable? {
+	public static func += (lhs: CompositeDisposable, rhs: @escaping @Sendable () -> Void) -> Disposable? {
 		return lhs.add(rhs)
 	}
 }
@@ -325,7 +326,7 @@ extension ScopedDisposable where Inner == CompositeDisposable {
 	/// - returns: An instance of `DisposableHandle` that can be used to opaquely
 	///            remove the disposable later (if desired).
 	@discardableResult
-	public static func += (lhs: ScopedDisposable<CompositeDisposable>, rhs: @escaping () -> Void) -> Disposable? {
+	public static func += (lhs: ScopedDisposable<CompositeDisposable>, rhs: @escaping @Sendable () -> Void) -> Disposable? {
 		return lhs.inner.add(rhs)
 	}
 }
@@ -334,7 +335,7 @@ extension ScopedDisposable where Inner == CompositeDisposable {
 /// wrapped disposable to be replaced.
 public final class SerialDisposable: Disposable {
 	private let _inner: Atomic<Disposable?>
-	private var state: UnsafeAtomicState<DisposableState>
+	private let state: UnsafeAtomicState<DisposableState>
 
 	public var isDisposed: Bool {
 		return state.is(.disposed)

Sources/Event.swift

@@ -206,27 +206,27 @@ extension Signal.Event: EventProtocol {
 //    This operator performs side effect upon interruption.
 
 extension Signal.Event {
-	internal typealias Transformation<U, E: Swift.Error> = (ReactiveSwift.Observer<U, E>, Lifetime) -> ReactiveSwift.Observer<Value, Error>
+	internal typealias Transformation<U, E: Swift.Error> = (any ReactiveSwift.Observer<U, E>, Lifetime) -> (any ReactiveSwift.Observer<Value, Error>)
 
-	internal static func filter(_ isIncluded: @escaping (Value) -> Bool) -> Transformation<Value, Error> {
+	internal static func filter(_ isIncluded: @escaping @Sendable (Value) -> Bool) -> Transformation<Value, Error> {
 		return { downstream, _ in
 			Operators.Filter(downstream: downstream, predicate: isIncluded)
 		}
 	}
 
-	internal static func compactMap<U>(_ transform: @escaping (Value) -> U?) -> Transformation<U, Error> {
+	internal static func compactMap<U>(_ transform: @escaping @Sendable (Value) -> U?) -> Transformation<U, Error> {
 		return { downstream, _ in
 			Operators.CompactMap(downstream: downstream, transform: transform)
 		}
 	}
 
-	internal static func map<U>(_ transform: @escaping (Value) -> U) -> Transformation<U, Error> {
+	internal static func map<U>(_ transform: @escaping @Sendable (Value) -> U) -> Transformation<U, Error> {
 		return { downstream, _ in
 			Operators.Map(downstream: downstream, transform: transform)
 		}
 	}
 
-	internal static func mapError<E>(_ transform: @escaping (Error) -> E) -> Transformation<Value, E> {
+	internal static func mapError<E>(_ transform: @escaping @Sendable (Error) -> E) -> Transformation<Value, E> {
 		return { downstream, _ in
 			Operators.MapError(downstream: downstream, transform: transform)
 		}
@@ -244,13 +244,13 @@ extension Signal.Event {
 		}
 	}
 
-	internal static func attemptMap<U>(_ transform: @escaping (Value) -> Result<U, Error>) -> Transformation<U, Error> {
+	internal static func attemptMap<U>(_ transform: @escaping @Sendable (Value) -> Result<U, Error>) -> Transformation<U, Error> {
 		return { downstream, _ in
 			Operators.AttemptMap(downstream: downstream, transform: transform)
 		}
 	}
 
-	internal static func attempt(_ action: @escaping (Value) -> Result<(), Error>) -> Transformation<Value, Error> {
+	internal static func attempt(_ action: @escaping @Sendable (Value) -> Result<(), Error>) -> Transformation<Value, Error> {
 		return attemptMap { value -> Result<Value, Error> in
 			return action(value).map { _ in value }
 		}
@@ -285,13 +285,13 @@ extension Signal.Event {
 		}
 	}
 
-	internal static func take(while shouldContinue: @escaping (Value) -> Bool) -> Transformation<Value, Error> {
+	internal static func take(while shouldContinue: @escaping @Sendable (Value) -> Bool) -> Transformation<Value, Error> {
 		return { downstream, _ in
 			Operators.TakeWhile(downstream: downstream, shouldContinue: shouldContinue)
 		}
 	}
 
-	internal static func take(until shouldContinue: @escaping (Value) -> Bool) -> Transformation<Value, Error> {
+	internal static func take(until shouldContinue: @escaping @Sendable (Value) -> Bool) -> Transformation<Value, Error> {
 		return { downstream, _ in
 			Operators.TakeUntil(downstream: downstream, shouldContinue: shouldContinue)
 		}
@@ -397,7 +397,7 @@ extension Signal.Event {
 		return scan(into: initialResult) { $0 = nextPartialResult($0, $1) }
 	}
 
-	internal static func scanMap<State, U>(into initialState: State, _ next: @escaping (inout State, Value) -> U) -> Transformation<U, Error> {
+	internal static func scanMap<State, U>(into initialState: State, _ next: @escaping @Sendable (inout State, Value) -> U) -> Transformation<U, Error> {
 		return { downstream, _ in
 			Operators.ScanMap(downstream: downstream, initial: initialState, next: next)
 		}

Sources/EventLogger.swift

@@ -31,7 +31,7 @@ public func defaultEventLog(identifier: String, event: String, fileName: String,
 
 /// A type that represents an event logging function.
 /// Signature is:
-///		- identifier 
+///		- identifier
 ///		- event
 ///		- fileName
 ///		- functionName
@@ -52,22 +52,22 @@ fileprivate struct LogContext<Event: LoggingEventProtocol> {
 	let functionName: String
 	let lineNumber: Int
 	let logger: EventLogger
-	
-	func log<T>(_ event: Event) -> ((T) -> Void)? {
+
+	func log<T>(_ event: Event) -> (@Sendable (T) -> Void)? {
 		return event.logIfNeeded(events: self.events) { event in
 			self.logger(self.identifier, event, self.fileName, self.functionName, self.lineNumber)
 		}
 	}
-	
-	func log(_ event: Event) -> (() -> Void)? {
+
+	func log(_ event: Event) -> (@Sendable () -> Void)? {
 		return event.logIfNeededNoArg(events: self.events) { event in
 			self.logger(self.identifier, event, self.fileName, self.functionName, self.lineNumber)
 		}
 	}
 }
 
 extension Signal {
-	/// Logs all events that the receiver sends. By default, it will print to 
+	/// Logs all events that the receiver sends. By default, it will print to
 	/// the standard output.
 	///
 	/// - parameters:
@@ -80,14 +80,21 @@ extension Signal {
 	///   - logger: Logger that logs the events.
 	///
 	/// - returns: Signal that, when observed, logs the fired events.
-	public func logEvents(identifier: String = "", events: Set<LoggingEvent.Signal> = Set(LoggingEvent.Signal.allCases), fileName: String = #file, functionName: String = #function, lineNumber: Int = #line, logger: @escaping EventLogger = defaultEventLog) -> Signal<Value, Error> {
+	public func logEvents(
+		identifier: String = "",
+		events: Set<LoggingEvent.Signal> = Set(LoggingEvent.Signal.allCases),
+		fileName: String = #file,
+		functionName: String = #function,
+		lineNumber: Int = #line,
+		logger: @escaping EventLogger = defaultEventLog
+	) -> Signal<Value, Error> {
 		let logContext = LogContext(events: events,
 		                            identifier: identifier,
 		                            fileName: fileName,
 		                            functionName: functionName,
 		                            lineNumber: lineNumber,
 		                            logger: logger)
-		
+
 		return self.on(
 			failed: logContext.log(.failed),
 			completed: logContext.log(.completed),
@@ -100,7 +107,7 @@ extension Signal {
 }
 
 extension SignalProducer {
-	/// Logs all events that the receiver sends. By default, it will print to 
+	/// Logs all events that the receiver sends. By default, it will print to
 	/// the standard output.
 	///
 	/// - parameters:
@@ -149,14 +156,14 @@ private extension LoggingEventProtocol {
 	//        Due to differences in the type checker, this method cannot
 	//        overload the generic `logIfNeeded`, or otherwise it would lead to
 	//        infinite recursion with Swift 4.0.x.
-	func logIfNeededNoArg(events: Set<Self>, logger: @escaping (String) -> Void) -> (() -> Void)? {
+	func logIfNeededNoArg(events: Set<Self>, logger: @escaping (String) -> Void) -> (@Sendable () -> Void)? {
 		return (self.logIfNeeded(events: events, logger: logger) as ((()) -> Void)?)
 			.map { closure in
-				{ closure(()) }
+				{ @Sendable in closure(()) }
 			}
 	}
-	
-	func logIfNeeded<T>(events: Set<Self>, logger: @escaping (String) -> Void) -> ((T) -> Void)? {
+
+	func logIfNeeded<T>(events: Set<Self>, logger: @escaping (String) -> Void) -> (@Sendable (T) -> Void)? {
 		guard events.contains(self) else {
 			return nil
 		}