Fix for #2365.

a soft reference around cached classes so they do not interfere with
garbage collection. There is a test case, but it is in pending because I
spent longer trying to get it to fail under partest than I did writing
the actual patch. If you would like to see the behavior which was
corrected, go to

  test/pending/run/bug2365

and run that script with scalac built before and after this commit.
Review by dubochet.

2 files changed, 7 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeDSL.scala b/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
index fb65f82740..a788015262 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
@@ -175,7 +175,10 @@ trait TreeDSL {
         if (target.tpe.typeSymbol == SomeClass) TRUE   // is Some[_]
         else NOT(ID(target) DOT nme.isEmpty)           // is Option[_]
 
-      def GET() = fn(ID(target), nme.get)
+      def IS_NULL() = REF(target) ANY_EQ NULL
+      def NOT_NULL() = REF(target) ANY_NE NULL
+
+      def GET() = fn(REF(target), nme.get)
 
       // name of nth indexed argument to a method (first parameter list), defaults to 1st
       def ARG(idx: Int = 0) = Ident(target.paramss.head(idx))
diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index c5a8b93c88..7f2bcf99c5 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -228,6 +228,9 @@ abstract class TreeGen
   def mkOr(tree1: Tree, tree2: Tree): Tree =
     Apply(Select(tree1, Boolean_or), List(tree2))
 
+  // wrap the given expression in a SoftReference so it can be gc-ed
+  def mkSoftRef(expr: Tree): Tree = New(TypeTree(SoftReferenceClass.tpe), List(List(expr)))
+
   def mkCached(cvar: Symbol, expr: Tree): Tree = {
     val cvarRef = if (cvar.owner.isClass) Select(This(cvar.owner), cvar) else Ident(cvar)
     Block(