As per discussion documented in SI-1799, brough...

As per discussion documented in SI-1799, brought back the ProductN
traits and synthesized them into case classes. It's -Xexperimental for
now because there may be minor implications for existing code which
should be discussed. And also because I snuck in another "improvement"
but it's probably too dangerous to be touching productIterator directly
and it should go into something else.

  scala> case class Bippy(x: Int, y: Int)
  defined class Bippy

  scala> Bippy(5, 10).productIterator
  res0: Iterator[Int] = non-empty iterator
                 ^^^----- as opposed to Iterator[Any]

There is an even better idea available than lubbing the case class field
types: it starts with "H" and ends with "List"...

Review by oderksy.

1 files changed, 15 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index a90cb6c409..f0d6f4c5bf 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -2649,6 +2649,20 @@ self =>
      *  }}}
      */
     def templateOpt(mods: Modifiers, name: Name, constrMods: Modifiers, vparamss: List[List[ValDef]], tstart: Int): Template = {
+      /** A synthetic ProductN parent for case classes. */
+      def extraCaseParents = (
+        if (settings.Xexperimental.value && mods.isCase) {
+          val arity = if (vparamss.isEmpty || vparamss.head.isEmpty) 0 else vparamss.head.size
+          if (arity == 0) Nil
+          else List(
+            AppliedTypeTree(
+              productConstrN(arity),
+              vparamss.head map (vd => vd.tpt)
+            )
+          )
+        }
+        else Nil
+      )
       val (parents0, argss, self, body) = (
         if (in.token == EXTENDS || in.token == SUBTYPE && mods.hasTraitFlag) {
           in.nextToken()
@@ -2673,7 +2687,7 @@ self =>
             else if (parents0.isEmpty) List(scalaAnyRefConstr)
             else parents0
           ) ++ (
-            if (mods.isCase) List(productConstr, serializableConstr)
+            if (mods.isCase) List(productConstr, serializableConstr) ++ extraCaseParents
             else Nil
           )