private static boolean isSimpleAssignment(PsiExpressionStatement expressionStatement, PsiField field) {
    final PsiExpression expression = expressionStatement.getExpression();
    if (!(expression instanceof PsiAssignmentExpression assignmentExpression)) {
      return false;
    }
    final PsiExpression lhs = PsiUtil.skipParenthesizedExprDown(assignmentExpression.getLExpression());
    if (!(lhs instanceof PsiReferenceExpression referenceExpression)) {
      return false;
    }
    if (!field.equals(referenceExpression.resolve())) {
      return false;
    }
    final PsiExpression rhs = assignmentExpression.getRExpression();
    final boolean safe = PsiTreeUtil.processElements(rhs, PsiReferenceExpression.class, ref -> {
      final PsiElement target = ref.resolve();
      return !(target instanceof PsiLocalVariable) && !(target instanceof PsiParameter);
    });
    if (!safe) {
      return false;
    }
    final PsiElement[] elements = rhs == null ? PsiElement.EMPTY_ARRAY : new PsiElement[] {rhs};
    final HashSet<PsiField> usedFields = new HashSet<>();
    final PsiClass targetClass = field.getContainingClass();
    return CommonJavaRefactoringUtil.canBeStatic(targetClass, expressionStatement, elements, usedFields) && usedFields.isEmpty();
  }
private static boolean isSimpleAssignment(PsiExpressionStatement expressionStatement, PsiField field)