Adding some Sets/Maps to perRunCaches, and elim...

Adding some Sets/Maps to perRunCaches, and eliminating ambiguously named
imports.

Did a tour of the compiler adding a few longer-lived mutable structures
to the per-run cache clearing mechanism. Some of these were not a big
threat, but there is (almost) literally no cost to tracking them and the
fewer mutable structures which are created "lone wolf style" the easier
it is to spot the one playing by his own rules.

While I was at it I followed through on long held ambition to eliminate
the importing of highly ambiguous names like "Map" and "HashSet" from
the mutable and immutable packages. I didn't quite manage elimination
but it's pretty close. Something potentially as pernicious which I
didn't do much about is this import:

  import scala.collection._

Imagine coming across that one on lines 407 and 474 of a 1271 file.
That's not cool. Some poor future programmer will be on line 1100 and
use "Map[A, B]" in some function and only after the product has shipped
will it be discovered that the signature is wrong and the rocket will
now be crashing into the mountainside straightaway. No review.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 29ca9f4a70..c0e78d716c 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -13,7 +13,7 @@ package typechecker
 
 import annotation.tailrec
 import scala.collection.{ mutable, immutable }
-import mutable.{ HashMap, LinkedHashMap, ListBuffer }
+import mutable.{ LinkedHashMap, ListBuffer }
 import scala.util.matching.Regex
 import symtab.Flags._
 import util.Statistics._
@@ -83,7 +83,7 @@ trait Implicits {
   private type InfoMap = LinkedHashMap[Symbol, List[ImplicitInfo]] // A map from class symbols to their associated implicits
   private val implicitsCache = new LinkedHashMap[Type, Infoss]
   private val infoMapCache = new LinkedHashMap[Symbol, InfoMap]
-  private val improvesCache = new HashMap[(ImplicitInfo, ImplicitInfo), Boolean]
+  private val improvesCache = perRunCaches.newMap[(ImplicitInfo, ImplicitInfo), Boolean]()
 
   def resetImplicits() {
     implicitsCache.clear()
@@ -175,7 +175,7 @@ trait Implicits {
   /** An extractor for types of the form ? { name: ? }
    */
   object HasMember {
-    private val hasMemberCache = new mutable.HashMap[Name, Type]
+    private val hasMemberCache = perRunCaches.newMap[Name, Type]()
     def apply(name: Name): Type = hasMemberCache.getOrElseUpdate(name, memberWildcardType(name, WildcardType))
     def unapply(pt: Type): Option[Name] = pt match {
       case RefinedType(List(WildcardType), decls) =>