From a43e6b1242018f538a25efd70e74ab87abc8691d Mon Sep 17 00:00:00 2001
From: Gilles Dubochet <gilles.dubochet@epfl.ch>
Date: Sun, 20 May 2007 16:05:38 +0000
Subject: Rich comparison (scala.runtime.Comparator.equal...
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Rich comparison (scala.runtime.Comparator.equals) is not inserted when
both sides of an equality are statically known to be equal and of a
subtype of Number or Character. This is an optimisation — behaviour
should be equivalent as their own equal methods should do ok.
---
 src/compiler/scala/tools/nsc/backend/icode/GenICode.scala | 15 +++++++++++----
 src/library/scala/runtime/Comparator.java                 |  4 ++--
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index b668e28c05..5ddf6b052d 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -1378,15 +1378,22 @@ abstract class GenICode extends SubComponent  {
           local
       }
 
+      /** True if the equality comparison is between values that require the use of the rich equality
+        * comparator (scala.runtime.Comparator.equals). This is the case when either side of the
+        * comparison might have a run-time type subtype of java.lang.Number or java.lang.Character.
+        * When it is statically known that both sides are equal and subtypes of Number of Character,
+        * not using the rich equality is possible (their own equals method will do ok.)*/
       def mustUseAnyComparator: Boolean = {
         val lsym = l.tpe.symbol
         val rsym = r.tpe.symbol
         (lsym == definitions.ObjectClass) ||
         (rsym == definitions.ObjectClass) ||
-        (lsym isNonBottomSubClass definitions.BoxedNumberClass)||
-        (!forMSIL && (lsym isNonBottomSubClass BoxedCharacterClass)) ||
-        (rsym isNonBottomSubClass definitions.BoxedNumberClass) ||
-        (!forMSIL && (rsym isNonBottomSubClass BoxedCharacterClass))
+        (lsym != rsym) && (
+          (lsym isNonBottomSubClass definitions.BoxedNumberClass) ||
+          (!forMSIL && (lsym isNonBottomSubClass BoxedCharacterClass)) ||
+          (rsym isNonBottomSubClass definitions.BoxedNumberClass) ||
+          (!forMSIL && (rsym isNonBottomSubClass BoxedCharacterClass))
+        )
       }
 
       if (mustUseAnyComparator) {
diff --git a/src/library/scala/runtime/Comparator.java b/src/library/scala/runtime/Comparator.java
index c73c7506ba..705bf30d5c 100644
--- a/src/library/scala/runtime/Comparator.java
+++ b/src/library/scala/runtime/Comparator.java
@@ -36,8 +36,8 @@ public class Comparator {
      *  ICode phase, method <code>genEqEqPrimitive</code>) only when either
      *  side of the comparison is a subclass of <code>AnyVal</code>, of
      *  <code>java.lang.Number</code>, of <code>java.lang.Character</code> or
-     *  is exactly <code>Any</code> or <code>AnyRef</code>.
-     */
+     *  is exactly <code>Any</code> or <code>AnyRef</code>, but when both sides
+     *  have different types. */
     public static boolean equals(Object a, Object b) {
         if (a == null)
             return b == null;
-- 
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