ProductN, and method synthesis toolbox.

- Finished giving case classes a ProductN parent, and flipped it on. The
"finish" part involved not breaking existing code where case classes
manually extend the appropriate ProductN. (Like, Tuple 1-22.)

- Generalized most of SyntheticMethods to ease method creation and class
manipulation in general.

- Fixed bugs related to the above, like the fact that this used to be a
compile error:

  scala> case class Foo() extends Serializable
  <console>:28: error: trait Serializable is inherited twice
         case class Foo() extends Serializable
                                  ^
It feels like there's a better way to eliminate the duplicate parents,
but after spending a lot of time chasing my tail in that peril-fraught
zone between namer and typer, I don't see an easy path to improve on
it.  Closes SI-1799.  For that modification to Typers, review by odersky.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index d4565c8e0c..89ec052556 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -287,6 +287,8 @@ abstract class RefChecks extends InfoTransform with reflect.internal.transform.R
                 infoStringWithLocation(other),
                 infoStringWithLocation(member)
               )
+            else if (settings.debug.value)
+              analyzer.foundReqMsg(member.tpe, other.tpe)
             else ""
 
           "overriding %s;\n %s %s%s".format(