21 files declare their use of Attribute

AttributesTest.php in drupal/core/tests/Drupal/Tests/Core/Common/AttributesTest.php
Contains \Drupal\Tests\Core\Common\AttributesTest.
block.admin.inc in drupal/core/modules/block/block.admin.inc
Admin page callbacks for the block module.
book.module in drupal/core/modules/book/book.module
Allows users to create and organize related content in an outline.
ckeditor.admin.inc in drupal/core/modules/ckeditor/ckeditor.admin.inc
Callbacks and theming for the CKEditor toolbar configuration UI.
common.inc in drupal/core/includes/common.inc
Common functions that many Drupal modules will need to reference.
datetime.module in drupal/core/modules/datetime/datetime.module
Field hooks to implement a simple datetime field.
DatetimeDefaultFormatter.php in drupal/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php
Contains \Drupal\datetime\Plugin\field\formatter\DateTimeDefaultFormatter.
field.module in drupal/core/modules/field/field.module
Attach custom data fields to Drupal entities.
file.module in drupal/core/modules/file/file.module
Defines a "managed_file" Form API field and a "file" field for Field module.
filter.module in drupal/core/modules/filter/filter.module
Framework for handling the filtering of content.
form.inc in drupal/core/includes/form.inc
Functions for form and batch generation and processing.
menu.inc in drupal/core/includes/menu.inc
API for the Drupal menu system.
node.module in drupal/core/modules/node/node.module
The core module that allows content to be submitted to the site.
pager.inc in drupal/core/includes/pager.inc
Functions to aid in presenting database results as a set of pages.
picture.module in drupal/core/modules/picture/picture.module
Picture display formatter for image fields.
rdf.module in drupal/core/modules/rdf/rdf.module
Enables semantically enriched output for Drupal sites in the form of RDFa.
theme.inc in drupal/core/includes/theme.inc
The theme system, which controls the output of Drupal.
toolbar.module in drupal/core/modules/toolbar/toolbar.module
Administration toolbar for quick access to top level administration items.
user.module in drupal/core/modules/user/user.module
Enables the user registration and login system.
views.theme.inc in drupal/core/modules/views/views.theme.inc
Preprocessors and helper functions to make theming easier.
views_ui.theme.inc in drupal/core/modules/views_ui/views_ui.theme.inc
Preprocessors and theme functions for the Views UI.