Better implementation of Predef.hash

2 files changed, 25 insertions, 2 deletions

diff --git a/src/library/scala/Predef.scala b/src/library/scala/Predef.scala
index c3f6ad9eff..df6cc61ee6 100644
--- a/src/library/scala/Predef.scala
+++ b/src/library/scala/Predef.scala
@@ -91,10 +91,10 @@ object Predef extends LowPriorityImplicits {
 
   def currentThread = java.lang.Thread.currentThread()
 
-  // hashcode and equality -------------------------------------------------
+  // hashcode -----------------------------------------------------------
 
   @inline def hash(x: Any): Int =
-    if (x.isInstanceOf[Number]) (x.asInstanceOf[Number]).intValue else x.hashCode
+    if (x.isInstanceOf[Number]) runtime.BoxesRunTime.numHash(x.asInstanceOf[Number]) else x.hashCode
 
   // errors and asserts -------------------------------------------------
 
diff --git a/src/library/scala/runtime/BoxesRunTime.java b/src/library/scala/runtime/BoxesRunTime.java
index b5df9d8ce8..c965bc2e95 100644
--- a/src/library/scala/runtime/BoxesRunTime.java
+++ b/src/library/scala/runtime/BoxesRunTime.java
@@ -178,6 +178,29 @@ public class BoxesRunTime
         return x.intValue() == ch;
     }
 
+    public static int numHash(Number n) {
+        if (n instanceof Long) {
+            int iv = n.intValue();
+            long lv = n.longValue();
+            if (lv == iv) return iv;
+        } else if (n instanceof Float) {
+            int iv = n.intValue();
+            float fv = n.floatValue();
+            if (fv == iv) return iv;
+            long lv = n.longValue();
+            if (fv == lv) return new Long(lv).hashCode();
+        } else if (n instanceof Double) {
+            int iv = n.intValue();
+            double dv = n.doubleValue();
+            if (dv == iv) return iv;
+            float fv = n.floatValue();
+            if (dv == fv) return new Float(fv).hashCode();
+            long lv = n.longValue();
+            if (dv == lv) return new Long(lv).hashCode();
+        }
+        return n.hashCode();
+    }
+
     private static boolean equalsBonusLogicFromScala27(Object a, Object b) {
         if (a instanceof Number || a instanceof Character || b instanceof Number || b instanceof Character) {
             int acode = typeCode(a);