9 files declare their use of BackupFileInterface in Backup and Migrate 8.4

BackupFile.php in lib/backup_migrate_core/src/File/BackupFile.php

DestinationBase.php in lib/backup_migrate_core/src/Destination/DestinationBase.php

DirectoryDestination.php in lib/backup_migrate_core/src/Destination/DirectoryDestination.php

DrupalBrowserUploadDestination.php in src/Destination/DrupalBrowserUploadDestination.php

ListableDestinationInterface.php in lib/backup_migrate_core/src/Destination/ListableDestinationInterface.php

ReadableDestinationInterface.php in lib/backup_migrate_core/src/Destination/ReadableDestinationInterface.php

SidecarMetadataDestinationTrait.php in lib/backup_migrate_core/src/Destination/SidecarMetadataDestinationTrait.php

StreamDestination.php in lib/backup_migrate_core/src/Destination/StreamDestination.php

TempFileManagerInterface.php in lib/backup_migrate_core/src/File/TempFileManagerInterface.php