HashCode for Set/MultiSet/Map should be independent of the order of the

elements.

1 files changed, 10 insertions, 8 deletions

diff --git a/Binaries/DafnyRuntime.cs b/Binaries/DafnyRuntime.cs
index 2a553c81..fd680a0b 100644
--- a/Binaries/DafnyRuntime.cs
+++ b/Binaries/DafnyRuntime.cs
@@ -75,9 +75,9 @@ namespace Dafny
       return other is Set<T> && Equals((Set<T>)other);

     }

     public override int GetHashCode() {

-      var hashCode = 0;

+      var hashCode = 1;

       foreach (var t in dict.Keys) {

-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ t.GetHashCode();

+        hashCode = hashCode * (t.GetHashCode()+3);

       }

       return hashCode;

     }

@@ -232,10 +232,11 @@ namespace Dafny
       return other is MultiSet<T> && Equals((MultiSet<T>)other);

     }

     public override int GetHashCode() {

-      var hashCode = 0;

+      var hashCode = 1;

       foreach (var kv in dict) {

-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Key.GetHashCode();

-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Value.GetHashCode();

+        var key = kv.Key.GetHashCode();

+        key = (key << 3) | (key >> 29) ^ kv.Value.GetHashCode();

+        hashCode = hashCode * (key + 3);

       }

       return hashCode;

     }

@@ -401,10 +402,11 @@ namespace Dafny
       return other is Map<U, V> && Equals((Map<U, V>)other);

     }

     public override int GetHashCode() {

-      var hashCode = 0;

+      var hashCode = 1;

       foreach (var kv in dict) {

-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Key.GetHashCode();

-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Value.GetHashCode();

+        var key = kv.Key.GetHashCode();

+        key = (key << 3) | (key >> 29) ^ kv.Value.GetHashCode();

+        hashCode = hashCode * (key + 3);

       }

       return hashCode;

     }