ScalaRunTime method to perform sameElements as ...

ScalaRunTime method to perform sameElements as fix for #2867. Review by
odersky.

3 files changed, 16 insertions, 17 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/Definitions.scala b/src/compiler/scala/tools/nsc/symtab/Definitions.scala
index 68c75a721a..3d969a53b4 100644
--- a/src/compiler/scala/tools/nsc/symtab/Definitions.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Definitions.scala
@@ -152,6 +152,7 @@ trait Definitions extends reflect.generic.StandardDefinitions {
       def arrayLengthMethod = getMember(ScalaRunTimeModule, "array_length")
       def arrayCloneMethod = getMember(ScalaRunTimeModule, "array_clone")
       def scalaRuntimeHash = getMember(ScalaRunTimeModule, "hash")
+      def scalaRuntimeSameElements = getMember(ScalaRunTimeModule, nme.sameElements)
 
     // classes with special meanings
     lazy val NotNullClass         = getClass("scala.NotNull")
diff --git a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
index 6a68ddc68c..042343ac16 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
@@ -180,23 +180,14 @@ trait SyntheticMethods extends ast.TreeDSL {
 
       // returns (Apply, Bind)
       def makeTrees(acc: Symbol, cpt: Type): (Tree, Bind) = {
-        val varName             = context.unit.fresh.newName(clazz.pos.focus, acc.name + "$")
-        val (eqMethod, binding) =
-          if (isRepeatedParamType(cpt))  (nme.sameElements, Star(WILD()))
-          else                           (nme.EQ          , WILD()      )
-
-        ((varName DOT eqMethod)(Ident(acc)), varName BIND binding)
-/** The three lines above were replaced by the following to fix #2867. But this makes lift fail, because
- *  an explicitly given type paramter violates its bound. Not sure what to do here.
- *
-          if (isRepeatedParamType(cpt))
-            (TypeApply(varName DOT nme.sameElements, List(TypeTree(cpt.baseType(SeqClass).typeArgs.head))),
-             Star(WILD()))
-          else
-            ((varName DOT nme.EQ): Tree,
-             WILD())
-        (eqMethod APPLY Ident(acc), varName BIND binding)
- */
+        val varName     = context.unit.fresh.newName(clazz.pos.focus, acc.name + "$")
+        val isRepeated  = isRepeatedParamType(cpt)
+        val binding     = if (isRepeated) Star(WILD()) else WILD()
+        val eqMethod: Tree  =
+          if (isRepeated) gen.mkRuntimeCall(nme.sameElements, List(Ident(varName), Ident(acc)))
+          else (varName DOT nme.EQ)(Ident(acc))
+
+        (eqMethod, varName BIND binding)
       }
 
       // Creates list of parameters and a guard for each
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 82573bf4b1..d04824bae1 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -179,6 +179,13 @@ object ScalaRunTime {
    */
   @inline def hash(x: Any): Int = Predef.hash(x)
 
+  /** A helper method for constructing case class equality methods,
+   *  because existential types get in the way of a clean outcome and
+   *  it's performing a series of Any/Any equals comparisons anyway.
+   *  See ticket #2867 for specifics.
+   */
+  def sameElements(xs1: Seq[Any], xs2: Seq[Any]) = xs1 sameElements xs2
+
   /** Given any Scala value, convert it to a String.
    *
    * The primary motivation for this method is to provide a means for