private void parseGuard(PsiBuilder builder) {
    if (builder.getTokenType() == JavaTokenType.IDENTIFIER && PsiKeyword.WHEN.equals(builder.getTokenText())) {
      builder.remapCurrentToken(JavaTokenType.WHEN_KEYWORD);
      builder.advanceLexer();
      PsiBuilder.Marker guardingExpression = myParser.getExpressionParser().parseAssignmentForbiddingLambda(builder);
      if (guardingExpression == null) {
        error(builder, JavaPsiBundle.message("expected.expression"));
      }
    }
  }
private void parseGuard(PsiBuilder builder)