Make the ownPhaseCache field a weak reference.

1 files changed, 11 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/SubComponent.scala b/src/compiler/scala/tools/nsc/SubComponent.scala
index 445021f22a..4fa9411357 100644
--- a/src/compiler/scala/tools/nsc/SubComponent.scala
+++ b/src/compiler/scala/tools/nsc/SubComponent.scala
@@ -5,6 +5,8 @@
 
 package scala.tools.nsc
 
+import scala.ref.WeakReference
+
 /** An nsc sub-component.
  *
  *  @author Martin Odersky
@@ -42,16 +44,20 @@ abstract class SubComponent {
   /** The phase factory */
   def newPhase(prev: Phase): Phase
 
-  private var ownPhaseCache: Phase = _
+  private var ownPhaseCache: WeakReference[Phase] = new WeakReference(null)
   private var ownPhaseRunId = global.NoRunId
 
   /** The phase corresponding to this subcomponent in the current compiler run */
   def ownPhase: Phase = {
-    if (ownPhaseRunId != global.currentRunId) {
-      ownPhaseCache = global.currentRun.phaseNamed(phaseName)
-      ownPhaseRunId = global.currentRunId
+    ownPhaseCache.get match {
+      case Some(phase) if ownPhaseRunId == global.currentRunId =>
+        phase
+      case _ =>
+        val phase = global.currentRun.phaseNamed(phaseName)
+        ownPhaseCache = new WeakReference(phase)
+        ownPhaseRunId = global.currentRunId
+        phase
     }
-    ownPhaseCache
   }
 
   /** The phase defined by this subcomponent. Can be called only after phase is installed by newPhase. */