Returning to the thrilling world of equality an...

Returning to the thrilling world of equality and hashCodes now
that Any.## is a reality. Moved the hash functions from Predef to
ScalaRunTime, and made what appears to be an optimization to equals by
not losing the result of an instanceof test. Review by community.

5 files changed, 123 insertions, 72 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
index 129a747e64..c4365a82ac 100644
--- a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
+++ b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
@@ -26,6 +26,9 @@ trait JavaPlatform extends Platform[AbstractFile] {
   ) ::: depAnalysisPhase
 
   lazy val externalEquals = getMember(BoxesRunTimeClass, nme.equals_)
+  def externalEqualsNumNum = getMember(BoxesRunTimeClass, "equalsNumNum")
+  def externalEqualsNumChar = getMember(BoxesRunTimeClass, "equalsNumChar")
+  def externalEqualsNumObject = getMember(BoxesRunTimeClass, "equalsNumObject")
 
   def isMaybeBoxed(sym: Symbol): Boolean = {
     import definitions._
diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index 64e6759da2..77e14139ba 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -9,7 +9,8 @@ package scala.tools.nsc
 package backend
 package icode
 
-import scala.collection.mutable.{Map, HashMap, ListBuffer, Buffer, HashSet}
+import scala.collection.{ mutable, immutable }
+import scala.collection.mutable.{ HashMap, ListBuffer, Buffer, HashSet }
 import scala.tools.nsc.symtab._
 import scala.annotation.switch
 import PartialFunction._
@@ -28,6 +29,7 @@ abstract class GenICode extends SubComponent  {
   import definitions.{
     ArrayClass, ObjectClass, ThrowableClass, StringClass, NothingClass, NullClass,
     Object_equals, Object_isInstanceOf, Object_asInstanceOf, ScalaRunTimeModule,
+    BoxedNumberClass, BoxedCharacterClass,
     getMember
   }
   import scalaPrimitives.{
@@ -1362,13 +1364,29 @@ abstract class GenICode extends SubComponent  {
         * 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 =
-        isMaybeBoxed(l.tpe.typeSymbol) && isMaybeBoxed(r.tpe.typeSymbol)
+      def mustUseAnyComparator: Boolean = {
+        def areSameFinals = l.tpe.isFinalType && r.tpe.isFinalType && (l.tpe =:= r.tpe)
+        !areSameFinals && isMaybeBoxed(l.tpe.typeSymbol) && isMaybeBoxed(r.tpe.typeSymbol)
+      }
 
       if (mustUseAnyComparator) {
         // when -optimise is on we call the @inline-version of equals, found in ScalaRunTime
         val equalsMethod =
-          if (!settings.XO.value) platform.externalEquals
+          if (!settings.XO.value) {
+            def default = platform.externalEquals
+            platform match {
+              case x: JavaPlatform =>
+                import x._
+                  if (l.tpe <:< BoxedNumberClass.tpe) {
+                    if (r.tpe <:< BoxedNumberClass.tpe) externalEqualsNumNum
+                    else if (r.tpe <:< BoxedCharacterClass.tpe) externalEqualsNumChar
+                    else externalEqualsNumObject
+                  }
+                  else default
+
+              case _ => default
+            }
+          }
           else {
             ctx.bb.emit(LOAD_MODULE(ScalaRunTimeModule))
             getMember(ScalaRunTimeModule, nme.inlinedEquals)
@@ -1603,7 +1621,7 @@ abstract class GenICode extends SubComponent  {
      *  to delay it any more: they will be used at some point.
      */
     class DuplicateLabels(boundLabels: collection.Set[Symbol]) extends Transformer {
-      val labels: Map[Symbol, Symbol] = new HashMap
+      val labels: mutable.Map[Symbol, Symbol] = new HashMap
       var method: Symbol = _
       var ctx: Context = _
 
@@ -2073,7 +2091,7 @@ abstract class GenICode extends SubComponent  {
        * jumps to the given basic block.
        */
       def patch(code: Code) {
-        def substMap: Map[Instruction, Instruction] = {
+        def substMap: mutable.Map[Instruction, Instruction] = {
           val map = new HashMap[Instruction, Instruction]()
 
           toPatch foreach (i => map += (i -> patch(i)))
diff --git a/src/library/scala/Predef.scala b/src/library/scala/Predef.scala
index 760d215d3f..d022b3e4a5 100644
--- a/src/library/scala/Predef.scala
+++ b/src/library/scala/Predef.scala
@@ -53,22 +53,6 @@ object Predef extends LowPriorityImplicits {
 
   @inline def locally[T](x: T): T = x
 
-  // hashcode -----------------------------------------------------------
-
-  @inline def hash(x: Any): Int =
-    if (x.isInstanceOf[Number]) runtime.BoxesRunTime.hashFromNumber(x.asInstanceOf[Number])
-    else x.hashCode
-
-  @inline def hash(x: Number): Int =
-    runtime.BoxesRunTime.hashFromNumber(x)
-
-  @inline def hash(x: java.lang.Long): Int = {
-    val iv = x.intValue
-    if (iv == x.longValue) iv else x.hashCode
-  }
-
-  @inline def hash(x: Int): Int = x
-
   // errors and asserts -------------------------------------------------
 
   def error(message: String): Nothing = throw new RuntimeException(message)
diff --git a/src/library/scala/runtime/BoxesRunTime.java b/src/library/scala/runtime/BoxesRunTime.java
index 087331e1c5..7c27835b5a 100644
--- a/src/library/scala/runtime/BoxesRunTime.java
+++ b/src/library/scala/runtime/BoxesRunTime.java
@@ -28,7 +28,7 @@ import scala.math.ScalaNumber;
   * @author  Martin Odersky
   * @contributor Stepan Koltsov
   * @version 2.0 */
-public class BoxesRunTime
+public final class BoxesRunTime
 {
     private static final int CHAR = 0, BYTE = 1, SHORT = 2, INT = 3, LONG = 4, FLOAT = 5, DOUBLE = 6, OTHER = 7;
 
@@ -136,38 +136,51 @@ public class BoxesRunTime
      *  in any case, we dispatch to it as soon as we spot one on either side.
      */
     public static boolean equals2(Object x, Object y) {
-        if (x instanceof Number) {
-            Number xn = (Number)x;
-
-            if (y instanceof Number) {
-                Number yn = (Number)y;
-                int xcode = eqTypeCode(xn);
-                int ycode = eqTypeCode(yn);
-                switch (ycode > xcode ? ycode : xcode) {
-                case INT:
-                    return xn.intValue() == yn.intValue();
-                case LONG:
-                    return xn.longValue() == yn.longValue();
-                case FLOAT:
-                    return xn.floatValue() == yn.floatValue();
-                case DOUBLE:
-                    return xn.doubleValue() == yn.doubleValue();
-                default:
-                    if ((yn instanceof ScalaNumber) && !(xn instanceof ScalaNumber))
-                        return y.equals(x);
-                }
-            } else if (y instanceof Character)
-                return equalsNumChar(xn, (Character)y);
-        } else if (x instanceof Character) {
-            Character xc = (Character)x;
-            if (y instanceof Character)
-                return xc.charValue() == ((Character)y).charValue();
-            if (y instanceof Number)
-                return equalsNumChar((Number)y, xc);
-        }
+        if (x instanceof Number)
+            return equalsNumObject((Number)x, y);
+        if (x instanceof Character)
+            return equalsCharObject((Character)x, y);
+
         return x.equals(y);
     }
 
+    public static boolean equalsNumObject(Number xn, Object y) {
+        if (y instanceof Number)
+            return equalsNumNum(xn, (Number)y);
+        else if (y instanceof Character)
+            return equalsNumChar(xn, (Character)y);
+
+        return xn.equals(y);
+    }
+
+    public static boolean equalsNumNum(Number xn, Number yn) {
+        int xcode = eqTypeCode(xn);
+        int ycode = eqTypeCode(yn);
+        switch (ycode > xcode ? ycode : xcode) {
+        case INT:
+            return xn.intValue() == yn.intValue();
+        case LONG:
+            return xn.longValue() == yn.longValue();
+        case FLOAT:
+            return xn.floatValue() == yn.floatValue();
+        case DOUBLE:
+            return xn.doubleValue() == yn.doubleValue();
+        default:
+            if ((yn instanceof ScalaNumber) && !(xn instanceof ScalaNumber))
+                return yn.equals(xn);
+        }
+        return xn.equals(yn);
+    }
+
+    public static boolean equalsCharObject(Character xc, Object y) {
+        if (y instanceof Character)
+            return xc.charValue() == ((Character)y).charValue();
+        if (y instanceof Number)
+            return equalsNumChar((Number)y, xc);
+
+        return xc.equals(y);
+    }
+
     private static boolean equalsNumChar(Number xn, Character yc) {
         char ch = yc.charValue();
         switch (eqTypeCode(xn)) {
@@ -212,27 +225,27 @@ public class BoxesRunTime
      *  verisons are equal.  This still needs reconciliation.
      */
     public static int hashFromLong(Long n) {
-      int iv = n.intValue();
-      if (iv == n.longValue()) return iv;
-      else return n.hashCode();
+        int iv = n.intValue();
+        if (iv == n.longValue()) return iv;
+        else return n.hashCode();
     }
     public static int hashFromDouble(Double n) {
-      int iv = n.intValue();
-      double dv = n.doubleValue();
-      if (iv == dv) return iv;
+        int iv = n.intValue();
+        double dv = n.doubleValue();
+        if (iv == dv) return iv;
 
-      long lv = n.longValue();
-      if (lv == dv) return Long.valueOf(lv).hashCode();
-      else return n.hashCode();
+        long lv = n.longValue();
+        if (lv == dv) return Long.valueOf(lv).hashCode();
+        else return n.hashCode();
     }
     public static int hashFromFloat(Float n) {
-      int iv = n.intValue();
-      float fv = n.floatValue();
-      if (iv == fv) return iv;
+        int iv = n.intValue();
+        float fv = n.floatValue();
+        if (iv == fv) return iv;
 
-      long lv = n.longValue();
-      if (lv == fv) return Long.valueOf(lv).hashCode();
-      else return n.hashCode();
+        long lv = n.longValue();
+        if (lv == fv) return Long.valueOf(lv).hashCode();
+        else return n.hashCode();
     }
     public static int hashFromNumber(Number n) {
       if (n instanceof Long) return hashFromLong((Long)n);
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index d04824bae1..43d60f2383 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -166,7 +166,8 @@ object ScalaRunTime {
   @inline def inlinedEquals(x: Object, y: Object): Boolean =
     if (x eq y) true
     else if (x eq null) false
-    else if (x.isInstanceOf[java.lang.Number] || x.isInstanceOf[java.lang.Character]) BoxesRunTime.equals2(x, y)
+    else if (x.isInstanceOf[java.lang.Number]) BoxesRunTime.equalsNumObject(x.asInstanceOf[java.lang.Number], y)
+    else if (x.isInstanceOf[java.lang.Character]) BoxesRunTime.equalsCharObject(x.asInstanceOf[java.lang.Character], y)
     else x.equals(y)
 
   def _equals(x: Product, y: Any): Boolean = y match {
@@ -174,10 +175,42 @@ object ScalaRunTime {
     case _                                              => false
   }
 
-  /** Just a stub for now, but I think this is where the Predef.hash
-   *  methods should be.
-   */
-  @inline def hash(x: Any): Int = Predef.hash(x)
+  // hashcode -----------------------------------------------------------
+
+  @inline def hash(x: Any): Int =
+    if (x.isInstanceOf[java.lang.Number]) BoxesRunTime.hashFromNumber(x.asInstanceOf[java.lang.Number])
+    else x.hashCode
+
+  @inline def hash(dv: Double): Int = {
+    val iv = dv.toInt
+    if (iv == dv) return iv
+
+    val lv = dv.toLong
+    if (lv == dv) return lv.hashCode
+    else dv.hashCode
+  }
+  @inline def hash(fv: Float): Int = {
+    val iv = fv.toInt
+    if (iv == fv) return iv
+
+    val lv = fv.toLong
+    if (lv == fv) return lv.hashCode
+    else fv.hashCode
+  }
+  @inline def hash(lv: Long): Int = {
+    val iv = lv.toInt
+    if (iv == lv) iv else lv.hashCode
+  }
+  @inline def hash(x: Int): Int = x
+  @inline def hash(x: Short): Int = x.toInt
+  @inline def hash(x: Byte): Int = x.toInt
+  @inline def hash(x: Char): Int = x.toInt
+
+  @inline def hash(x: Number): Int  = runtime.BoxesRunTime.hashFromNumber(x)
+  @inline def hash(x: java.lang.Long): Int = {
+    val iv = x.intValue
+    if (iv == x.longValue) iv else x.hashCode
+  }
 
   /** A helper method for constructing case class equality methods,
    *  because existential types get in the way of a clean outcome and