--- /dev/null
+<?php
+
+namespace Drupal\entity;
+
+use Drupal\Core\Field\BaseFieldDefinition;
+
+/**
+ * Provides a field definition class for bundle fields.
+ *
+ * Core currently doesn't provide one, the hook_entity_bundle_field_info()
+ * example uses BaseFieldDefinition, which is wrong. Tracked in #2346347.
+ *
+ * Note that this class implements both FieldStorageDefinitionInterface and
+ * FieldDefinitionInterface. This is a simplification for DX reasons,
+ * allowing code to return just the bundle definitions instead of having to
+ * return both storage definitions and bundle definitions.
+ */
+class BundleFieldDefinition extends BaseFieldDefinition {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function isBaseField() {
+ return FALSE;
+ }
+
+}