Null out closure in LazyBodyAnnotation

Author: odersky

compiler/src/dotty/tools/dotc/core/Annotations.scala

@@ -61,14 +61,15 @@ object Annotations {
     def tree(implicit ctx: Context) = body
   }
 
-  case class LazyBodyAnnotation(bodyExpr: Context => Tree) extends BodyAnnotation {
+  case class LazyBodyAnnotation(private var bodyExpr: Context => Tree) extends BodyAnnotation {
     private var evaluated = false
     private var myBody: Tree = _
     def tree(implicit ctx: Context) = {
       if (evaluated) assert(myBody != null)
       else {
         evaluated = true
         myBody = bodyExpr(ctx)
+        bodyExpr = null
       }
       myBody
     }