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/reflect/internal/BaseTypeSeqs.scala b/src/compiler/scala/reflect/internal/BaseTypeSeqs.scala
index bb342cf0e1..38277b5a09 100644
--- a/src/compiler/scala/reflect/internal/BaseTypeSeqs.scala
+++ b/src/compiler/scala/reflect/internal/BaseTypeSeqs.scala
@@ -6,7 +6,7 @@ package scala.reflect
 package internal
 
 // todo implement in terms of BitSet
-import scala.collection.mutable.{ListBuffer, BitSet}
+import scala.collection.{ mutable, immutable }
 import math.max
 import util.Statistics._
 
@@ -41,7 +41,7 @@ trait BaseTypeSeqs {
     // (while NoType is in there to indicate a cycle in this BTS, during the execution of
     //  the mergePrefixAndArgs below, the elems get copied without the pending map,
     //  so that NoType's are seen instead of the original type --> spurious compile error)
-    val pending = new BitSet(length)
+    val pending = new mutable.BitSet(length)
 
     /** The type at i'th position in this sequence; lazy types are returned evaluated. */
     def apply(i: Int): Type =
@@ -187,7 +187,7 @@ trait BaseTypeSeqs {
     val tsym = tp.typeSymbol
     val parents = tp.parents
 //    Console.println("computing baseTypeSeq of " + tsym.tpe + " " + parents)//DEBUG
-    val buf = new ListBuffer[Type]
+    val buf = new mutable.ListBuffer[Type]
     buf += tsym.tpe
     var btsSize = 1
     if (parents.nonEmpty) {