All classes that implement SelectionInterface in Entity reference 8

class \Drupal\entityreference\Plugin\Type\Selection\SelectionBroken implements SelectionInterface
class \Drupal\entityreference\Plugin\Type\Selection\SelectionEntityTypeComment
class \Drupal\entityreference\Plugin\Type\Selection\SelectionEntityTypeFile
class \Drupal\entityreference\Plugin\Type\Selection\SelectionEntityTypeNode
class \Drupal\entityreference\Plugin\Type\Selection\SelectionEntityTypeTaxonomyTerm
class \Drupal\entityreference\Plugin\Type\Selection\SelectionEntityTypeUser
class \Drupal\entityreference\Plugin\entityreference\selection\SelectionBase implements SelectionInterface

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