From 0e197e89ac96ec0dd8b136de8e07ad2e15f94371 Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Wed, 9 May 2012 15:01:26 -0700
Subject: Custom hashCode methods for case classes.

No boxing, no MODULE$ indirection.
---
 .../scala/reflect/internal/Definitions.scala       |  1 +
 .../tools/nsc/typechecker/SyntheticMethods.scala   | 35 +++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

(limited to 'src/compiler')

diff --git a/src/compiler/scala/reflect/internal/Definitions.scala b/src/compiler/scala/reflect/internal/Definitions.scala
index 1c3e11b040..edafde1346 100644
--- a/src/compiler/scala/reflect/internal/Definitions.scala
+++ b/src/compiler/scala/reflect/internal/Definitions.scala
@@ -896,6 +896,7 @@ trait Definitions extends reflect.api.StandardDefinitions {
     // boxed classes
     lazy val ObjectRefClass         = requiredClass[scala.runtime.ObjectRef[_]]
     lazy val VolatileObjectRefClass = requiredClass[scala.runtime.VolatileObjectRef[_]]
+    lazy val RuntimeStaticsModule   = getRequiredModule("scala.runtime.Statics")
     lazy val BoxesRunTimeModule     = getRequiredModule("scala.runtime.BoxesRunTime")
     lazy val BoxesRunTimeClass      = BoxesRunTimeModule.moduleClass
     lazy val BoxedNumberClass       = getClass(sn.BoxedNumber)
diff --git a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
index 57e82ed706..484c8beb1b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
@@ -89,6 +89,11 @@ trait SyntheticMethods extends ast.TreeDSL {
     def forwardToRuntime(method: Symbol): Tree =
       forwardMethod(method, getMember(ScalaRunTimeModule, method.name prepend "_"))(mkThis :: _)
 
+    def callStaticsMethod(name: String)(args: Tree*): Tree = {
+      val method = termMember(RuntimeStaticsModule, name)
+      Apply(gen.mkAttributedRef(method), args.toList)
+    }
+
     // Any member, including private
     def hasConcreteImpl(name: Name) =
       clazz.info.member(name).alternatives exists (m => !m.isDeferred && !m.isSynthetic)
@@ -222,13 +227,41 @@ trait SyntheticMethods extends ast.TreeDSL {
       )
     }
 
+    def hashcodeImplementation(sym: Symbol): Tree = {
+      sym.tpe.finalResultType.typeSymbol match {
+        case UnitClass | NullClass                         => Literal(Constant(0))
+        case BooleanClass                                  => If(Ident(sym), Literal(Constant(1231)), Literal(Constant(1237)))
+        case IntClass | ShortClass | ByteClass | CharClass => Ident(sym)
+        case LongClass                                     => callStaticsMethod("longHash")(Ident(sym))
+        case DoubleClass                                   => callStaticsMethod("doubleHash")(Ident(sym))
+        case FloatClass                                    => callStaticsMethod("floatHash")(Ident(sym))
+        case _                                             => callStaticsMethod("anyHash")(Ident(sym))
+      }
+    }
+
+    def specializedHashcode = {
+      createMethod(nme.hashCode_, Nil, IntClass.tpe) { m =>
+        val accumulator = m.newVariable(newTermName("acc"), m.pos, SYNTHETIC) setInfo IntClass.tpe
+        val valdef      = ValDef(accumulator, Literal(Constant(0xcafebabe)))
+        val mixes       = accessors map (acc =>
+          Assign(
+            Ident(accumulator),
+            callStaticsMethod("mix")(Ident(accumulator), hashcodeImplementation(acc))
+          )
+        )
+        val finish = callStaticsMethod("finalizeHash")(Ident(accumulator), Literal(Constant(arity)))
+
+        Block(valdef :: mixes, finish)
+      }
+    }
+
     def valueClassMethods = List(
       Any_hashCode -> (() => hashCodeDerivedValueClassMethod),
       Any_equals -> (() => equalsDerivedValueClassMethod)
     )
 
     def caseClassMethods = productMethods ++ productNMethods ++ Seq(
-      Object_hashCode -> (() => forwardToRuntime(Object_hashCode)),
+      Object_hashCode -> (() => specializedHashcode),
       Object_toString -> (() => forwardToRuntime(Object_toString)),
       Object_equals   -> (() => equalsCaseClassMethod)
     )
-- 
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