TreeUnpickler: do not capture Context in Annotation symbol

Author: smarter

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

@@ -117,11 +117,17 @@ object Annotations {
       }
 
     /** Create an annotation where the symbol and the tree are computed lazily. */
-    def deferredSymAndTree(sym: => Symbol, treeFn: Context => Tree)(implicit ctx: Context): Annotation =
+    def deferredSymAndTree(symf: Context => Symbol, treeFn: Context => Tree)(implicit ctx: Context): Annotation =
       new LazyAnnotation {
-        lazy val symf = sym
-
-        override def symbol(implicit ctx: Context): Symbol = symf
+        private[this] var mySym: Symbol = _
+
+        override def symbol(implicit ctx: Context): Symbol = {
+          if (mySym == null) {
+            mySym = symf(ctx)
+            assert(mySym != null)
+          }
+          mySym
+        }
         def complete(implicit ctx: Context) = treeFn(ctx)
       }
 

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -554,7 +554,9 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, posUnpickle
             val end = readEnd()
             val tp = readType()
             val lazyAnnotTree = readLater(end, rdr => ctx => rdr.readTerm()(ctx))
-            annots += Annotation.deferredSymAndTree(tp.typeSymbol, implicit ctx => lazyAnnotTree.complete)
+            annots += Annotation.deferredSymAndTree(
+              implicit ctx => tp.typeSymbol,
+              implicit ctx => lazyAnnotTree.complete)
           case tag =>
             assert(false, s"illegal modifier tag $tag at $currentAddr, end = $end")
         }