Reimplement Zip to fix reference crash issue (#5)

* Reimplement Zip to fix reference crash issue

* Add a test case for the documentation demo

* Fix wasm platform build issue

RemainingCombineInterface.swift

@@ -901,52 +901,3 @@ extension Publishers.MergeMany : Equatable where Upstream : Equatable {
     ///   - rhs: Another value to compare.
     public static func == (lhs: Publishers.MergeMany<Upstream>, rhs: Publishers.MergeMany<Upstream>) -> Bool
 }
-
-extension Publishers.Zip : Equatable where A : Equatable, B : Equatable {
-
-    /// Returns a Boolean value that indicates whether two publishers are equivalent.
-    ///
-    /// - Parameters:
-    ///   - lhs: A zip publisher to compare for equality.
-    ///   - rhs: Another zip publisher to compare for equality.
-    /// - Returns: `true` if the corresponding upstream publishers of each zip publisher are equal, `false` otherwise.
-    public static func == (lhs: Publishers.Zip<A, B>, rhs: Publishers.Zip<A, B>) -> Bool
-}
-
-/// Returns a Boolean value that indicates whether two publishers are equivalent.
-///
-/// - Parameters:
-///   - lhs: A zip publisher to compare for equality.
-///   - rhs: Another zip publisher to compare for equality.
-/// - Returns: `true` if the corresponding upstream publishers of each zip publisher are equal, `false` otherwise.
-extension Publishers.Zip3 : Equatable where A : Equatable, B : Equatable, C : Equatable {
-
-    /// Returns a Boolean value indicating whether two values are equal.
-    ///
-    /// Equality is the inverse of inequality. For any values `a` and `b`,
-    /// `a == b` implies that `a != b` is `false`.
-    ///
-    /// - Parameters:
-    ///   - lhs: A value to compare.
-    ///   - rhs: Another value to compare.
-    public static func == (lhs: Publishers.Zip3<A, B, C>, rhs: Publishers.Zip3<A, B, C>) -> Bool
-}
-
-/// Returns a Boolean value that indicates whether two publishers are equivalent.
-///
-/// - Parameters:
-///   - lhs: A zip publisher to compare for equality.
-///   - rhs: Another zip publisher to compare for equality.
-/// - Returns: `true` if the corresponding upstream publishers of each zip publisher are equal, `false` otherwise.
-extension Publishers.Zip4 : Equatable where A : Equatable, B : Equatable, C : Equatable, D : Equatable {
-
-    /// Returns a Boolean value indicating whether two values are equal.
-    ///
-    /// Equality is the inverse of inequality. For any values `a` and `b`,
-    /// `a == b` implies that `a != b` is `false`.
-    ///
-    /// - Parameters:
-    ///   - lhs: A value to compare.
-    ///   - rhs: Another value to compare.
-    public static func == (lhs: Publishers.Zip4<A, B, C, D>, rhs: Publishers.Zip4<A, B, C, D>) -> Bool
-}

Sources/OpenCombine/Helpers/Violations.swift

@@ -30,4 +30,10 @@ extension Subscribers.Demand {
         precondition(rawValue <= Subscribers.Demand.unlimited.rawValue)
         precondition(rawValue > Subscribers.Demand.none.rawValue)
     }
+
+    @_transparent
+    @inline(__always)
+    internal func assertValid() {
+        precondition(rawValue <= Subscribers.Demand.unlimited.rawValue)
+    }
 }

Sources/OpenCombine/Publishers/Publishers.Throttle.swift

@@ -103,6 +103,15 @@ extension Publishers {
             self.latest = latest
         }
 
+        /// Attaches the specified subscriber to this publisher.
+        ///
+        /// Implementations of ``Publisher`` must implement this method.
+        ///
+        /// The provided implementation of ``Publisher/subscribe(_:)-199o9``calls
+        /// this method.
+        ///
+        /// - Parameter subscriber: The subscriber to attach to this ``Publisher``,
+        ///     after which it can receive values.
         // swiftlint:disable generic_type_name
         public func receive<S>(subscriber: S)
         where S: Subscriber, Upstream.Failure == S.Failure, Upstream.Output == S.Input