Added a -Yno-productN option.

Suppresses ProductN parent for case classes. No review.

Author: paulp

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -2687,7 +2687,7 @@ self =>
         if (mods.isCase) {
           val arity = if (vparamss.isEmpty || vparamss.head.isEmpty) 0 else vparamss.head.size
           productConstr :: serializableConstr :: {
-            if (arity == 0) Nil
+            if (arity == 0 || settings.YnoProductN.value) Nil
             else List(
               AppliedTypeTree(
                 productConstrN(arity),

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -175,6 +175,7 @@ trait ScalaSettings extends AbsScalaSettings
   val YvirtClasses  = false // too embryonic to even expose as a -Y //BooleanSetting    ("-Yvirtual-classes", "Support virtual classes")
 
   val exposeEmptyPackage = BooleanSetting("-Yexpose-empty-package", "Internal only: expose the empty package.").internalOnly()
+  val YnoProductN = BooleanSetting ("-Yno-productN", "Do not add ProductN to case classes")
 
   def stop = stopAfter
 

test/files/pos/noproductN.flags

@@ -0,0 +1 @@
+-Yno-productN

test/files/pos/noproductN.scala

@@ -0,0 +1,2 @@
+object Foo { type  S = String }
+case class Foo(x: Foo.S) { }