private void checkExpression(PsiExpression operand) {
      operand = PsiUtil.skipParenthesizedExprDown(operand);
      if (!(operand instanceof PsiReferenceExpression referenceExpression)) {
        return;
      }
      final PsiElement target = referenceExpression.resolve();
      if (target instanceof PsiField) {
        mutatedField = ((PsiField)target).getName();
        stopWalking();
      }
    }
private void checkExpression(PsiExpression operand)