18 files declare their use of FormBuilderInterface

AjaxFormBlock.php in core/modules/system/tests/modules/ajax_forms_test/src/Plugin/Block/AjaxFormBlock.php
AreaDisplayLinkTest.php in core/modules/views/tests/src/Kernel/Handler/AreaDisplayLinkTest.php
BlockListBuilder.php in core/modules/block/src/BlockListBuilder.php
EntityFormBuilder.php in core/lib/Drupal/Core/Entity/EntityFormBuilder.php
FormAjaxSubscriber.php in core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php
FormAjaxSubscriberTest.php in core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php
FormBuilderTest.php in core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
FormController.php in core/lib/Drupal/Core/Controller/FormController.php
HtmlEntityFormController.php in core/lib/Drupal/Core/Entity/HtmlEntityFormController.php
HtmlFormController.php in core/lib/Drupal/Core/Controller/HtmlFormController.php
MigrateMessageController.php in core/modules/migrate/src/Controller/MigrateMessageController.php
PathAliasListBuilder.php in core/modules/path/src/PathAliasListBuilder.php
RedirectFormBlock.php in core/modules/system/tests/modules/form_test/src/Plugin/Block/RedirectFormBlock.php
RenderElementBase.php in core/lib/Drupal/Core/Render/Element/RenderElementBase.php
RenderElementTest.php in core/tests/Drupal/Tests/Core/Render/Element/RenderElementTest.php
SystemController.php in core/modules/system/src/Controller/SystemController.php
TimezoneTest.php in core/tests/Drupal/KernelTests/Core/Datetime/Element/TimezoneTest.php
UserLoginBlock.php in core/modules/user/src/Plugin/Block/UserLoginBlock.php

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