From 879e05964dbc6d9b91f25d54594825491085f0e9 Mon Sep 17 00:00:00 2001
From: freak4pc <freak4pc@gmail.com>
Date: Tue, 26 Mar 2019 16:20:14 +0200
Subject: [PATCH] Use Hashable's `hash(into:)` when available

---
 Sources/Differentiator/Diff.swift     | 18 ++++++++++++------
 Sources/Differentiator/ItemPath.swift |  9 +++++++--
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/Sources/Differentiator/Diff.swift b/Sources/Differentiator/Diff.swift
index b1ff3948..b9938171 100644
--- a/Sources/Differentiator/Diff.swift
+++ b/Sources/Differentiator/Diff.swift
@@ -126,21 +126,22 @@ public enum Diff {
     //================================================================================
     // swift dictionary optimizations {
 
-    private struct OptimizedIdentity<E: Hashable> : Hashable {
-
+    private struct OptimizedIdentity<E: Hashable>: Hashable {
+        #if swift(>=4.2)
+        #else
         let hashValue: Int
+        #endif
         let identity: UnsafePointer<E>
 
         init(_ identity: UnsafePointer<E>) {
             self.identity = identity
+            #if swift(>=4.2)
+            #else
             self.hashValue = identity.pointee.hashValue
+            #endif
         }
 
         static func == (lhs: OptimizedIdentity<E>, rhs: OptimizedIdentity<E>) -> Bool {
-            if lhs.hashValue != rhs.hashValue {
-                return false
-            }
-
             if lhs.identity.distance(to: rhs.identity) == 0 {
                 return true
             }
@@ -148,6 +149,11 @@ public enum Diff {
             return lhs.identity.pointee == rhs.identity.pointee
         }
 
+        #if swift(>=4.2)
+        public func hash(into hasher: inout Hasher) {
+            hasher.combine(self.identity.pointee)
+        }
+        #endif
     }
 
     private static func calculateAssociatedData<Item: IdentifiableType>(
diff --git a/Sources/Differentiator/ItemPath.swift b/Sources/Differentiator/ItemPath.swift
index 9551e112..3ae7b610 100644
--- a/Sources/Differentiator/ItemPath.swift
+++ b/Sources/Differentiator/ItemPath.swift
@@ -27,9 +27,14 @@ public func == (lhs: ItemPath, rhs: ItemPath) -> Bool {
 }
 
 extension ItemPath: Hashable {
-
+    #if swift(>=4.2)
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(sectionIndex.byteSwapped)
+        hasher.combine(itemIndex)
+    }
+    #else
     public var hashValue: Int {
         return sectionIndex.byteSwapped.hashValue ^ itemIndex.hashValue
     }
-    
+    #endif
 }