Warn when Any or AnyVal is inferred.

For the very small price of annotating types as Any/AnyVal in those
cases where we wish to use them, we can obtain useful warnings.
I made trunk clean against this warning and found several bugs
or at least suboptimalities in the process.

I put the warning behind -Xlint for the moment, but I think this
belongs on by default, even for this alone:

  scala> List(1, 2, 3) contains "a"
  <console>:8: warning: a type was inferred to be `Any`; this may indicate a programming error.
                List(1, 2, 3) contains "a"
                                       ^
  res0: Boolean = false

Or this punishment meted out by SI-4042:

  scala> 1l to 5l contains 5
  <console>:8: warning: a type was inferred to be `AnyVal`; this may indicate a programming error.
                1l to 5l contains 5
                                  ^
  res0: Boolean = false

A different situation where this arises, which I have seen variations
of many times:

  scala> class A[T](default: T) {
    def get(x: => Option[T]) = x getOrElse Some(default)
  }
  <console>:7: warning: a type was inferred to be `Any`; this may indicate a programming error.
         class A[T](default: T) { def get(x: => Option[T]) = x getOrElse Some(default) }
                                                                             ^
  // Oops, this was what I meant
  scala> class A[T](default: T) {
    def get(x: => Option[T]) = x getOrElse default
  }
  defined class A

Harder to avoid spurious warnings when "Object" is inferred.

2 files changed, 2 insertions, 2 deletions

diff --git a/src/swing/scala/swing/ComboBox.scala b/src/swing/scala/swing/ComboBox.scala
index c7a457d082..67e39cfe3b 100644
--- a/src/swing/scala/swing/ComboBox.scala
+++ b/src/swing/scala/swing/ComboBox.scala
@@ -182,7 +182,7 @@ class ComboBox[A](items: Seq[A]) extends Component with Publisher {
    * of the component to its own defaults _after_ the renderer has been
    * configured. That's Swing's principle of most suprise.
    */
-  def renderer: ListView.Renderer[A] = ListView.Renderer.wrap(peer.getRenderer)
+  def renderer: ListView.Renderer[A] = ListView.Renderer.wrap[A](peer.getRenderer)
   def renderer_=(r: ListView.Renderer[A]) { peer.setRenderer(r.peer) }
 
   /* XXX: currently not safe to expose:
diff --git a/src/swing/scala/swing/ListView.scala b/src/swing/scala/swing/ListView.scala
index 282d24696e..22850bac42 100644
--- a/src/swing/scala/swing/ListView.scala
+++ b/src/swing/scala/swing/ListView.scala
@@ -216,7 +216,7 @@ class ListView[A] extends Component {
     def adjusting = peer.getSelectionModel.getValueIsAdjusting
   }
 
-  def renderer: ListView.Renderer[A] = ListView.Renderer.wrap(peer.getCellRenderer)
+  def renderer: ListView.Renderer[A] = ListView.Renderer.wrap[A](peer.getCellRenderer)
   def renderer_=(r: ListView.Renderer[A]) { peer.setCellRenderer(r.peer) }
 
   def fixedCellWidth = peer.getFixedCellWidth