// where
 private String expr2String(JCExpression tree) {
   switch (tree.getTag()) {
     case PARENS:
       return expr2String(((JCParens) tree).expr);
     case LAMBDA:
     case REFERENCE:
     case CONDEXPR:
       return Pretty.toSimpleString(tree);
     default:
       Assert.error("unexpected tree kind " + tree.getKind());
       return null;
   }
 }
 public String formatPosition(JCDiagnostic d, PositionKind pk, Locale l) {
   Assert.check(d.getPosition() != Position.NOPOS);
   return String.valueOf(getPosition(d, pk));
 }