Support Hashable (#19)

Author: muukii

Sources/StateStruct/CopyOnWrite.swift

@@ -1,4 +1,7 @@
 
+/**
+ non-atomic
+ */
 public final class _BackingStorage<Value>: @unchecked Sendable {
 
   public var value: Value
@@ -15,6 +18,11 @@ extension _BackingStorage: Equatable where Value: Equatable {
   }  
 }
 
+extension _BackingStorage: Hashable where Value: Hashable {
+  public func hash(into hasher: inout Hasher) {
+    value.hash(into: &hasher)
+  }
+}
 
 #if DEBUG
 private struct Before {

Sources/StateStruct/Source.swift

@@ -57,6 +57,11 @@ public macro COWTrackingProperty() =
     var count: Int = 0
   }
 
+@Tracking
+struct HashableState: Hashable {
+  var count: Int = 0
+}
+
   @Tracking
   struct MyState {
 

Sources/StateStruct/Tracking.swift

@@ -10,14 +10,18 @@ extension Array {
 }
 
 
-public final class _TrackingContext: Sendable, Equatable {
+public final class _TrackingContext: Sendable, Hashable {
 
   public static func == (lhs: _TrackingContext, rhs: _TrackingContext) -> Bool {
     // ``_TrackingContext`` is used only for embedding into the struct.
     // It always returns true when checked for equality to prevent
     // interfering with the actual equality check of the struct.
     return true
   }
+  
+  public func hash(into hasher: inout Hasher) {
+    0.hash(into: &hasher)
+  }
 
   @inlinable
   public var path: PropertyPath? {