Move Extension fields to the Swift 4.2 Hashable approach.

ExtensionFieldValueSet is the problem case, as AnyExtensionField isn't
actually Hashable, so we have to build the support manually.

Author: thomasvl

Sources/SwiftProtobuf/ExtensionFieldValueSet.swift

@@ -39,6 +39,22 @@ public struct ExtensionFieldValueSet: Hashable {
 
   public init() {}
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    // AnyExtensionField is not Hashable, and the Self constraint that would
+    // add breaks some of the uses of it; so the only choice is to manually
+    // mix things in. However, one must remember to do things in an order
+    // independent manner.
+    var hash = 16777619
+    for (fieldNumber, v) in values {
+      var localHasher = hasher
+      localHasher.combine(fieldNumber)
+      v.hash(into: &localHasher)
+      hash = hash &+ localHasher.finalize()
+    }
+    hasher.combine(hash)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     var hash = 16777619
     for (fieldNumber, v) in values {
@@ -47,6 +63,7 @@ public struct ExtensionFieldValueSet: Hashable {
     }
     return hash
   }
+#endif  // swift(>=4.2)
 
   public func traverse<V: Visitor>(visitor: inout V, start: Int, end: Int) throws {
     let validIndexes = values.keys.filter {$0 >= start && $0 < end}

Sources/SwiftProtobuf/ExtensionFields.swift

@@ -12,8 +12,10 @@
 ///
 // -----------------------------------------------------------------------------
 
+#if !swift(>=4.2)
 private let i_2166136261 = Int(bitPattern: 2166136261)
 private let i_16777619 = Int(16777619)
+#endif
 
 //
 // Type-erased Extension field implementation.
@@ -26,7 +28,11 @@ private let i_16777619 = Int(16777619)
 // so you can't actually access the contained value itself.
 //
 public protocol AnyExtensionField: CustomDebugStringConvertible {
+#if swift(>=4.2)
+  func hash(into hasher: inout Hasher)
+#else
   var hashValue: Int { get }
+#endif
   var protobufExtension: AnyMessageExtension { get }
   func isEqual(other: AnyExtensionField) -> Bool
 
@@ -81,9 +87,15 @@ public struct OptionalExtensionField<T: FieldType>: ExtensionField {
     }
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get { return value.hashValue }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! OptionalExtensionField<T>
@@ -132,6 +144,11 @@ public struct RepeatedExtensionField<T: FieldType>: ExtensionField {
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -141,6 +158,7 @@ public struct RepeatedExtensionField<T: FieldType>: ExtensionField {
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! RepeatedExtensionField<T>
@@ -190,6 +208,11 @@ public struct PackedExtensionField<T: FieldType>: ExtensionField {
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -199,6 +222,7 @@ public struct PackedExtensionField<T: FieldType>: ExtensionField {
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! PackedExtensionField<T>
@@ -251,9 +275,15 @@ public struct OptionalEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
     }
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get { return value.hashValue }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! OptionalEnumExtensionField<E>
@@ -304,6 +334,11 @@ public struct RepeatedEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -313,6 +348,7 @@ public struct RepeatedEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! RepeatedEnumExtensionField<E>
@@ -364,6 +400,11 @@ public struct PackedEnumExtensionField<E: Enum>: ExtensionField where E.RawValue
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value)
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -373,6 +414,7 @@ public struct PackedEnumExtensionField<E: Enum>: ExtensionField where E.RawValue
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! PackedEnumExtensionField<E>
@@ -428,7 +470,13 @@ public struct OptionalMessageExtensionField<M: Message & Equatable>:
     }
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value.hashValue) // TODO(thomasvl): Fix this once message is updated!
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {return value.hashValue}
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! OptionalMessageExtensionField<M>
@@ -480,6 +528,13 @@ public struct RepeatedMessageExtensionField<M: Message & Equatable>:
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    for e in value {
+      hasher.combine(e.hashValue) // TODO(thomasvl): Fix this once message is updated!
+    }
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -489,6 +544,7 @@ public struct RepeatedMessageExtensionField<M: Message & Equatable>:
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public func isEqual(other: AnyExtensionField) -> Bool {
     let o = other as! RepeatedMessageExtensionField<M>
@@ -544,7 +600,13 @@ public struct OptionalGroupExtensionField<G: Message & Hashable>:
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(value.hashValue) // TODO(thomasvl): Fix this once message is updated!
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {return value.hashValue}
+#endif  // swift(>=4.2)
 
   public var debugDescription: String { get {return value.debugDescription} }
 
@@ -598,6 +660,13 @@ public struct RepeatedGroupExtensionField<G: Message & Hashable>:
     self.value = value
   }
 
+#if swift(>=4.2)
+  public func hash(into hasher: inout Hasher) {
+    for e in value {
+      hasher.combine(e.hashValue) // TODO(thomasvl): Fix this once message is updated!
+    }
+  }
+#else  // swift(>=4.2)
   public var hashValue: Int {
     get {
       var hash = i_2166136261
@@ -607,6 +676,7 @@ public struct RepeatedGroupExtensionField<G: Message & Hashable>:
       return hash
     }
   }
+#endif  // swift(>=4.2)
 
   public var debugDescription: String {
     return "[" + value.map{$0.debugDescription}.joined(separator: ",") + "]"