Changing the intersectionWitness map to use wea...

Changing the intersectionWitness map to use weak references for the
value. A value may prevent parts of this map from collecting, since
the value may hold a (strong) reference to one of the keys in the map.
review by odersky.

3 files changed, 9 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/interactive/Global.scala b/src/compiler/scala/tools/nsc/interactive/Global.scala
index 8af350c8b7..99619e3a2f 100644
--- a/src/compiler/scala/tools/nsc/interactive/Global.scala
+++ b/src/compiler/scala/tools/nsc/interactive/Global.scala
@@ -39,6 +39,7 @@ self =>
     else NullLogger
 
   import log.logreplay
+  debugLog("logger: " + log.getClass + " writing to " + (new java.io.File(logName)).getAbsolutePath)
 
   /** Print msg only when debugIDE is true. */
   @inline final def debugLog(msg: => String) =
diff --git a/src/compiler/scala/tools/nsc/symtab/Types.scala b/src/compiler/scala/tools/nsc/symtab/Types.scala
index ef45834ab7..e3fb82385b 100644
--- a/src/compiler/scala/tools/nsc/symtab/Types.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Types.scala
@@ -8,6 +8,7 @@ package symtab
 
 import scala.collection.{ mutable, immutable }
 import scala.collection.mutable.ListBuffer
+import scala.ref.WeakReference
 import ast.TreeGen
 import util.{ Position, NoPosition }
 import util.Statistics._
@@ -150,7 +151,7 @@ trait Types extends reflect.generic.Types { self: SymbolTable =>
    *  It makes use of the fact that these two operations depend only on the parents,
    *  not on the refinement.
    */
-  val intersectionWitness = new mutable.WeakHashMap[List[Type], Type]
+  val intersectionWitness = new mutable.WeakHashMap[List[Type], WeakReference[Type]]
 
   private object gen extends {
     val global : Types.this.type = Types.this
@@ -1341,12 +1342,12 @@ trait Types extends reflect.generic.Types { self: SymbolTable =>
       baseClassesCache
     }
 
-    def memo[A](op1: => A)(op2: Type => A) = intersectionWitness get parents match {
-      case Some(w) =>
-        if (w eq this) op1 else op2(w)
-      case none =>
-        intersectionWitness(parents) = this
+    def memo[A](op1: => A)(op2: Type => A) = {
+      (for (ref <- intersectionWitness.get(parents); w <- ref.get)
+         yield if (w eq this) op1 else op2(w)) getOrElse {
+        intersectionWitness(parents) = new WeakReference(this)
         op1
+      }
     }
 
     override def baseType(sym: Symbol): Type = {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index bcb2767e6f..784531ba1e 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -49,6 +49,7 @@ trait Typers extends Modes {
     resetNamer()
     resetImplicits()
     transformed.clear()
+    //println("%,d entries in intersectionWitness".format(intersectionWitness.size))
   }
 
   object UnTyper extends Traverser {