Overhaul of Namers.

I can't go bear hunting without a clean gun. Basically I iterated over
Namers until I could understand it. I added a variety of documentation
there and elsewhere. There shouldn't be anything particularly behavioral
changing in this commit, but I did delete some years-old code (having
huge commented out blocks of way-out-of-date code is not a boon to
understanding) and the debugging output will look different. Better, one
can hope.

How about, review by moors.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
index 42f8188ac1..080a802272 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
@@ -451,6 +451,10 @@ trait TypeDiagnostics {
 
     private def contextError(pos: Position, msg: String) = context.error(pos, msg)
     private def contextError(pos: Position, err: Throwable) = context.error(pos, err)
+    private def contextWarning(pos: Position, msg: String) = context.unit.warning(pos, msg)
+
+    def permanentlyHiddenWarning(pos: Position, hidden: Name, defn: Symbol) =
+      contextWarning(pos, "imported `%s' is permanently hidden by definition of %s".format(hidden, defn.fullLocationString))
 
     object checkDead {
       private var expr: Symbol = NoSymbol