Removes redundant outers

Widens the criterion when outer fields can be omitted. It used to be that sub- and superclass had to be enclosed by the same outer class. Only in that case was the outer field of the class omitted. We now omit if subclass is contained in an outer class that is itself a subclass of the superclasses outer class.

See test case "outertest.scala" for an example.

src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala

@@ -46,10 +46,13 @@ abstract class ExplicitOuter extends InfoTransform
   private def haveSameOuter(parent: Type, clazz: Symbol) = parent match {
     case TypeRef(pre, sym, _)   =>
       val owner = clazz.owner
+
+      //println(s"have same outer $parent $clazz $sym ${sym.owner} $owner $pre")
 
       sym.isClass && owner.isClass &&
-      owner == sym.owner &&
+      (owner isSubClass sym.owner) && 
       owner.thisType =:= pre
+
     case _                      => false
   }
 
@@ -480,7 +483,7 @@ abstract class ExplicitOuter extends InfoTransform
                 val vparamss1 =
                   if (isInner(clazz)) { // (4)
                     val outerParam =
-                      sym.newValueParameter(nme.OUTER, sym.pos) setInfo outerField(clazz).info
+                      sym.newValueParameter(nme.OUTER, sym.pos) setInfo clazz.outerClass.thisType
                     ((ValDef(outerParam) setType NoType) :: vparamss.head) :: vparamss.tail
                   } else vparamss
                 super.transform(copyDefDef(tree)(vparamss = vparamss1))

test/files/run/outertest.scala

@@ -0,0 +1,26 @@
+// A test for the case where the outer field of class B#J should be eliminated.
+// You can verify this by running a javap on B.J
+abstract class A {
+
+  abstract class I {
+
+  }
+
+  val foo = "foo"
+
+}
+
+class B extends A {
+
+  class J extends I {
+    val bar = foo
+  }
+
+}
+
+object  Test extends App {
+
+  val b = new B
+  assert((new b.J).bar == b.foo)
+
+}