Add primary associated types to property and binding protocols (#888)

* Add primary associated types to property and binding protocols

- PropertyProtocol
- MutablePropertyProtocol
- ComposableMutablePropertyProtocol
- BindingSource
- BindingTargetProvider

* Add entry to change log

* Remove instructional text from the previous version in changelog

* Replace uses of 'bond' with 'bound' in doc comments

Author: braker1nine

CHANGELOG.md

@@ -1,11 +1,10 @@
 # master
 *Please add new entries at the top.*
+1. Add primary associated types to property and binding protocols (#888, kudos to @braker1nine)
 1. Fix the Carthage build checks (kudos to @mluisbrown)
 1. Add dynamic library support for SPM (#886 kudos to @mluisbrown)
 
 # 7.2.0
-*Please add new entries at the top.*
-
 1. Change `QueueScheduler` to use unspecified QoS when QoS parameter is defaulted (#880, kudos to @jamieQ)
 1. Add support for visionOS (#875, kudos to @NachoSoto)
 1. Fix CI release git tag push trigger (#869, kudos to @p4checo)

Sources/Property.swift

@@ -7,6 +7,35 @@ import Glibc
 // FIXME: The `Error == Never` constraint is retained for Swift 4.0.x
 //        compatibility, since `BindingSource` did not impose such constraint
 //        due to the absence of conditional conformance.
+#if swift(>=5.7)
+
+/// Represents a property that allows observation of its changes.
+///
+/// Only classes can conform to this protocol, because having a signal
+/// for changes over time implies the origin must have a unique identity.
+public protocol PropertyProtocol<Value>: AnyObject, BindingSource {
+	/// The current value of the property.
+	var value: Value { get }
+	
+	/// The values producer of the property.
+	///
+	/// It produces a signal that sends the property's current value,
+	/// followed by all changes over time. It completes when the property
+	/// has deinitialized, or has no further change.
+	///
+	/// - note: If `self` is a composed property, the producer would be
+	///         bound to the lifetime of its sources.
+	var producer: SignalProducer<Value, Never> { get }
+	
+	/// A signal that will send the property's changes over time. It
+	/// completes when the property has deinitialized, or has no further
+	/// change.
+	///
+	/// - note: If `self` is a composed property, the signal would be
+	///         bound to the lifetime of its sources.
+	var signal: Signal<Value, Never> { get }
+}
+#else
 
 /// Represents a property that allows observation of its changes.
 ///
@@ -34,7 +63,20 @@ public protocol PropertyProtocol: AnyObject, BindingSource {
 	///         bound to the lifetime of its sources.
 	var signal: Signal<Value, Never> { get }
 }
+#endif
 
+#if swift(>=5.7)
+/// Represents an observable property that can be mutated directly.
+public protocol MutablePropertyProtocol<Value>: PropertyProtocol, BindingTargetProvider {
+	associatedtype Value 
+	
+	/// The current value of the property.
+	var value: Value { get set }
+	
+	/// The lifetime of the property.
+	var lifetime: Lifetime { get }
+}
+#else
 /// Represents an observable property that can be mutated directly.
 public protocol MutablePropertyProtocol: PropertyProtocol, BindingTargetProvider {
 	/// The current value of the property.
@@ -43,6 +85,7 @@ public protocol MutablePropertyProtocol: PropertyProtocol, BindingTargetProvider
 	/// The lifetime of the property.
 	var lifetime: Lifetime { get }
 }
+#endif
 
 /// Default implementation of `BindingTargetProvider` for mutable properties.
 extension MutablePropertyProtocol {
@@ -51,6 +94,29 @@ extension MutablePropertyProtocol {
 	}
 }
 
+#if swift(>=5.7)
+/// Represents a mutable property that can be safety composed by exposing its
+/// synchronization mechanic through the defined closure-based interface.
+public protocol ComposableMutablePropertyProtocol<Value>: MutablePropertyProtocol {
+	/// Atomically performs an arbitrary action using the current value of the
+	/// variable.
+	///
+	/// - parameters:
+	///   - action: A closure that accepts current property value.
+	///
+	/// - returns: the result of the action.
+	func withValue<Result>(_ action: (Value) throws -> Result) rethrows -> Result
+	
+	/// Atomically modifies the variable.
+	///
+	/// - parameters:
+	///   - action: A closure that accepts old property value and returns a new
+	///             property value.
+	///
+	/// - returns: The result of the action.
+	func modify<Result>(_ action: (inout Value) throws -> Result) rethrows -> Result
+}
+#else
 /// Represents a mutable property that can be safety composed by exposing its
 /// synchronization mechanic through the defined closure-based interface.
 public protocol ComposableMutablePropertyProtocol: MutablePropertyProtocol {
@@ -72,6 +138,7 @@ public protocol ComposableMutablePropertyProtocol: MutablePropertyProtocol {
 	/// - returns: The result of the action.
 	func modify<Result>(_ action: (inout Value) throws -> Result) rethrows -> Result
 }
+#endif
 
 // Property operators.
 //

Sources/UnidirectionalBinding.swift

@@ -10,17 +10,31 @@ precedencegroup BindingPrecedence {
 
 infix operator <~ : BindingPrecedence
 
+#if swift(>=5.7)
+/// Describes a source which can be bound.
+public protocol BindingSource<Value>: SignalProducerConvertible where Error == Never {}
+#else
 /// Describes a source which can be bound.
 public protocol BindingSource: SignalProducerConvertible where Error == Never {}
+#endif
 extension Signal: BindingSource where Error == Never {}
 extension SignalProducer: BindingSource where Error == Never {}
 
-/// Describes an entity which be bond towards.
+#if swift(>=5.7)
+/// Describes an entity which be bound towards.
+public protocol BindingTargetProvider<Value> {
+	associatedtype Value
+	
+	var bindingTarget: BindingTarget<Value> { get }
+}
+#else
+/// Describes an entity which be bound towards.
 public protocol BindingTargetProvider {
 	associatedtype Value
 
 	var bindingTarget: BindingTarget<Value> { get }
 }
+#endif
 
 extension BindingTargetProvider {
 	/// Binds a source to a target, updating the target's value to the latest
@@ -46,7 +60,7 @@ extension BindingTargetProvider {
 	/// ````
 	///
 	/// - parameters:
-	///   - target: A target to be bond to.
+	///   - target: A target to be bound to.
 	///   - source: A source to bind.
 	///
 	/// - returns: A disposable that can be used to terminate binding before the
@@ -86,7 +100,7 @@ extension BindingTargetProvider {
 	/// ````
 	///
 	/// - parameters:
-	///   - target: A target to be bond to.
+	///   - target: A target to be bound to.
 	///   - source: A source to bind.
 	///
 	/// - returns: A disposable that can be used to terminate binding before the
@@ -111,7 +125,7 @@ extension Signal.Observer {
 	///         deinitialized, or when the source sends a `completed` event.
 	///
 	/// - parameters:
-	///   - target: A target to be bond to.
+	///   - target: A target to be bound to.
 	///   - source: A source to bind.
 	///
 	/// - returns: A disposable that can be used to terminate binding before the