Removing unnecessary AnyVal code.

...since it works from source. The parser must be forcibly restrained
from adding a bogus constructor, but other than that it's pretty much
smooth sailing.  To give an idea how smooth, if I change scala.Short like so:

  trait Bippy extends Any
  final class Short extends AnyVal with Bippy

Then it just works, at least until the fiction is revealed.

  scala> def f(x: Bippy) = x
  f: (x: Bippy)Bippy

  scala> f(5)
  <console>:9: error: type mismatch;
   found   : Int(5)
   required: Bippy
                f(5)
                  ^

  scala> f(5: Short)
  java.lang.ClassCastException: java.lang.Short cannot be cast to scala.Bippy
  	at .<init>(<console>:9)
  	at .<clinit>(<console>)
  	at .<init>(<console>:11)

1 files changed, 11 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
index e7759f1d7e..531a475bc6 100644
--- a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
+++ b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
@@ -302,21 +302,19 @@ abstract class AddInterfaces extends InfoTransform {
       yield mixinConstructorCall(implClass(mc))
     }
     tree match {
+      case Block(Nil, expr) =>
+        // AnyVal constructor - have to provide a real body so the
+        // jvm doesn't throw a VerifyError. But we can't add the
+        // body until now, because the typer knows that Any has no
+        // constructor and won't accept a call to super.init.
+        assert((clazz isSubClass AnyValClass) || clazz.info.parents.isEmpty, clazz)
+        val superCall = Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), Nil)
+        Block(List(superCall), expr)
+
       case Block(stats, expr) =>
         // needs `hasSymbol` check because `supercall` could be a block (named / default args)
-        stats span (t => t.hasSymbolWhich(_ hasFlag PRESUPER)) match {
-          case (presuper, supercall :: rest) =>
-            stats span (t => t.hasSymbolWhich(_ hasFlag PRESUPER))
-            treeCopy.Block(tree, presuper ::: (supercall :: mixinConstructorCalls ::: rest), expr)
-          case (Nil, Nil) =>
-            assert(clazz eq AnyValClass, clazz)
-            // AnyVal constructor - have to provide a real body so the
-            // jvm doesn't throw a VerifyError. But we can't add the
-            // body until now, because the typer knows that Any has no
-            // constructor and won't accept a call to super.init.
-            val superCall = Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), Nil)
-            Block(List(superCall), Literal(Constant()))
-        }
+        val (presuper, supercall :: rest) = stats span (t => t.hasSymbolWhich(_ hasFlag PRESUPER))
+        treeCopy.Block(tree, presuper ::: (supercall :: mixinConstructorCalls ::: rest), expr)
     }
   }