@Override
    public void visitLiteralExpression(
      @NotNull PsiLiteralExpression value) {
      super.visitLiteralExpression(value);
      final String text = value.getText();
      if (!PsiKeyword.NULL.equals(text)) {
        return;
      }
      PsiElement parent = value.getParent();
      while (parent instanceof PsiParenthesizedExpression ||
             parent instanceof PsiConditionalExpression ||
             parent instanceof PsiTypeCastExpression) {
        parent = parent.getParent();
      }
      if (!(parent instanceof PsiAssignmentExpression assignmentExpression)) {
        return;
      }
      final PsiExpression lhs = PsiUtil.skipParenthesizedExprDown(assignmentExpression.getLExpression());
      if (lhs == null || isReferenceToNullableVariable(lhs)) {
        return;
      }
      registerError(lhs, lhs);
    }
@Override
    public void visitLiteralExpression(
      @NotNull PsiLiteralExpression value)