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, 25 insertions, 2 deletions

diff --git a/src/compiler/scala/reflect/internal/SymbolTable.scala b/src/compiler/scala/reflect/internal/SymbolTable.scala
index ca2b5867ce..32fa88ac15 100644
--- a/src/compiler/scala/reflect/internal/SymbolTable.scala
+++ b/src/compiler/scala/reflect/internal/SymbolTable.scala
@@ -116,6 +116,9 @@ abstract class SymbolTable extends api.Universe
 
   object perRunCaches {
     import java.lang.ref.WeakReference
+    import scala.tools.util.Signallable
+    import scala.runtime.ScalaRunTime.stringOf
+
 
     // We can allow ourselves a structural type, these methods
     // amount to a few calls per run at most.  This does suggest
@@ -128,6 +131,25 @@ abstract class SymbolTable extends api.Universe
     // letting us know when a cache is really out of commission.
     private val caches = mutable.HashSet[WeakReference[Clearable]]()
 
+    private def dumpCaches() {
+      println(caches.size + " structures are in perRunCaches.")
+      caches.zipWithIndex foreach { case (ref, index) =>
+        val cache = ref.get()
+        println("(" + index + ")" + (
+          if (cache == null) " has been collected."
+          else " has " + cache.size + " entries:\n" + stringOf(cache)
+        ))
+      }
+    }
+    if (settings.debug.value) {
+      println(Signallable("dump compiler caches")(dumpCaches()))
+    }
+
+    def recordCache[T <: Clearable](cache: T): T = {
+      caches += new WeakReference(cache)
+      cache
+    }
+
     def clearAll() = {
       if (settings.debug.value) {
         val size = caches flatMap (ref => Option(ref.get)) map (_.size) sum;
@@ -142,8 +164,9 @@ abstract class SymbolTable extends api.Universe
       }
     }
 
-    def newMap[K, V]() = { val m = mutable.HashMap[K, V]() ; caches += new WeakReference(m) ; m }
-    def newSet[K]()    = { val s = mutable.HashSet[K]() ; caches += new WeakReference(s) ; s }
+    def newWeakMap[K, V]() = recordCache(mutable.WeakHashMap[K, V]())
+    def newMap[K, V]()     = recordCache(mutable.HashMap[K, V]())
+    def newSet[K]()        = recordCache(mutable.HashSet[K]())
   }
 
   /** Break into repl debugger if assertion is true. */