16 files declare their use of FieldConfigInterface

comment.module in core/modules/comment/comment.module
Enables users to comment on published content.
config_translation.module in core/modules/config_translation/config_translation.module
Configuration Translation module.
field.module in core/modules/field/field.module
Attach custom data fields to Drupal entities.
FieldConfig.php in core/modules/field/src/Entity/FieldConfig.php
FieldConfigEditForm.php in core/modules/field_ui/src/Form/FieldConfigEditForm.php
FieldConfigListBuilder.php in core/modules/field_ui/src/FieldConfigListBuilder.php
image.module in core/modules/image/image.module
Exposes global functionality for creating image styles.
ImageFormatterBase.php in core/modules/image/src/Plugin/Field/FieldFormatter/ImageFormatterBase.php
layout_builder.module in core/modules/layout_builder/layout_builder.module
Provides hook implementations for Layout Builder.
media.module in core/modules/media/media.module
Provides media items.
MediaUiJavascriptTest.php in core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
MigrateBlockContentBodyFieldTest.php in core/modules/block_content/tests/src/Kernel/Migrate/MigrateBlockContentBodyFieldTest.php
MigrateFieldInstanceTest.php in core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldInstanceTest.php
MigrateNodeTypeTest.php in core/modules/node/tests/src/Kernel/Migrate/d7/MigrateNodeTypeTest.php
NumberFieldTest.php in core/modules/field/tests/src/Functional/Number/NumberFieldTest.php
views.views.inc in core/modules/views/views.views.inc
Provide views data that isn't tied to any other module.

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