Make printing of capture sets work also when testing Pickler

Author: odersky

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -640,7 +640,9 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           try changePrec(GlobalPrec)(toText(arg) ~ "^" ~ toTextCaptureSet(captureSet))
           catch case ex: IllegalCaptureRef => toTextAnnot
         if annot.symbol.maybeOwner == defn.RetainsAnnot
-            && Feature.ccEnabled && Config.printCaptureSetsAsPrefix && !printDebug
+            && Feature.ccEnabled
+            && Config.printCaptureSetsAsPrefix && !printDebug
+            && Phases.checkCapturesPhase.exists // might be missing on -Ytest-pickler
         then toTextRetainsAnnot
         else toTextAnnot
       case EmptyTree =>