diff --git a/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php b/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
index 8157dc6..7e20bfc 100644
--- a/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
+++ b/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
@@ -18,10 +18,10 @@
   /**
    * Returns the field entity for this instance.
    *
-   * @return \Drupal\field\FieldInterface
+   * @return \Drupal\field\FieldConfigInterface
    *   The field entity for this instance.
    */
-  public function getField();
+  public function getFieldConfig();
 
   /**
    * Allows a bundle to be renamed.
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstanceConfig.php b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstanceConfig.php
index 476404e..d4072e8 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstanceConfig.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstanceConfig.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\field\Plugin\Core\Entity\FieldInstance.
+ * Contains \Drupal\field\Plugin\Core\Entity\FieldInstanceConfig.
  */
 
 namespace Drupal\field\Plugin\Core\Entity;
@@ -191,7 +191,7 @@ class FieldInstanceConfig extends ConfigEntityBase implements FieldInstanceConfi
    *
    * @var \Drupal\field\Plugin\Core\Entity\FieldConfig
    */
-  protected $field_config;
+  protected $fieldConfig;
 
   /**
    * Flag indicating whether the bundle name can be renamed or not.
@@ -258,7 +258,7 @@ public function __construct(array $values, $entity_type = 'field_instance_config
     // At this point, we should have a 'field_uuid' and a FieldConfig. Ditch the
     // 'field_name' property if it was provided, and assign the $field property.
     unset($values['field_name']);
-    $this->field_config = $field;
+    $this->fieldConfig = $field;
 
     // Discard the 'field_type' entry that is added in config records to ease
     // schema generation. See getExportProperties().
@@ -266,16 +266,16 @@ public function __construct(array $values, $entity_type = 'field_instance_config
 
     // Check required properties.
     if (empty($values['entity_type'])) {
-      throw new FieldException(format_string('Attempt to create an instance of field @field_id without an entity type.', array('@field_id' => $this->field_config->id)));
+      throw new FieldException(format_string('Attempt to create an instance of field @field_id without an entity type.', array('@field_id' => $this->fieldConfig->id)));
     }
     if (empty($values['bundle'])) {
-      throw new FieldException(format_string('Attempt to create an instance of field @field_id without a bundle.', array('@field_id' => $this->field_config->id)));
+      throw new FieldException(format_string('Attempt to create an instance of field @field_id without a bundle.', array('@field_id' => $this->fieldConfig->id)));
     }
 
     // 'Label' defaults to the field ID (mostly useful for field instances
     // created in tests).
     $values += array(
-      'label' => $this->field_config->id,
+      'label' => $this->fieldConfig->id,
     );
     parent::__construct($values, $entity_type);
   }
@@ -284,7 +284,7 @@ public function __construct(array $values, $entity_type = 'field_instance_config
    * {@inheritdoc}
    */
   public function id() {
-    return $this->entity_type . '.' . $this->bundle . '.' . $this->field_config->id;
+    return $this->entity_type . '.' . $this->bundle . '.' . $this->fieldConfig->id;
   }
 
   /**
@@ -313,7 +313,7 @@ public function getExportProperties() {
 
     // Additionally, include the field type, that is needed to be able to
     // generate the field-type-dependant parts of the config schema.
-    $properties['field_type'] = $this->field_config->type;
+    $properties['field_type'] = $this->fieldConfig->type;
 
     return $properties;
   }
@@ -356,8 +356,8 @@ protected function saveNew() {
     $instance_controller = \Drupal::entityManager()->getStorageController($this->entityType);
 
     // Check that the field can be attached to this entity type.
-    if (!empty($this->field_config->entity_types) && !in_array($this->entity_type, $this->field_config->entity_types)) {
-      throw new FieldException(format_string('Attempt to create an instance of field @field_id on forbidden entity type @entity_type.', array('@field_id' => $this->field_config->id, '@entity_type' => $this->entity_type)));
+    if (!empty($this->fieldConfig->entity_types) && !in_array($this->entity_type, $this->fieldConfig->entity_types)) {
+      throw new FieldException(format_string('Attempt to create an instance of field @field_id on forbidden entity type @entity_type.', array('@field_id' => $this->fieldConfig->id, '@entity_type' => $this->entity_type)));
     }
 
     // Assign the ID.
@@ -365,7 +365,7 @@ protected function saveNew() {
 
     // Ensure the field instance is unique within the bundle.
     if ($prior_instance = $instance_controller->load($this->id)) {
-      throw new FieldException(format_string('Attempt to create an instance of field @field_id on bundle @bundle that already has an instance of that field.', array('@field_id' => $this->field_config->id, '@bundle' => $this->bundle)));
+      throw new FieldException(format_string('Attempt to create an instance of field @field_id on bundle @bundle that already has an instance of that field.', array('@field_id' => $this->fieldConfig->id, '@bundle' => $this->bundle)));
     }
 
     // Set the field UUID.
@@ -425,7 +425,7 @@ protected function saveUpdated() {
    * Prepares the instance definition for saving.
    */
   protected function prepareSave() {
-    $field_type_info = field_info_field_types($this->field_config->type);
+    $field_type_info = field_info_field_types($this->fieldConfig->type);
 
     // Set the default instance settings.
     $this->settings += $field_type_info['instance_settings'];
@@ -460,11 +460,11 @@ public function delete($field_cleanup = TRUE) {
 
       // Mark instance data for deletion by invoking
       // hook_field_storage_delete_instance().
-      $module_handler->invoke($this->field_config->storage['module'], 'field_storage_delete_instance', array($this));
+      $module_handler->invoke($this->fieldConfig->storage['module'], 'field_storage_delete_instance', array($this));
 
       // Remove the instance from the entity form displays.
       if ($form_display = entity_load('entity_form_display', $this->entity_type . '.' . $this->bundle . '.default')) {
-        $form_display->removeComponent($this->field_config->id())->save();
+        $form_display->removeComponent($this->fieldConfig->id())->save();
       }
 
       // Remove the instance from the entity displays.
@@ -474,12 +474,12 @@ public function delete($field_cleanup = TRUE) {
         $ids[] = $this->entity_type . '.' . $this->bundle . '.' . $view_mode;
       }
       foreach (entity_load_multiple('entity_display', $ids) as $display) {
-        $display->removeComponent($this->field_config->id())->save();
+        $display->removeComponent($this->fieldConfig->id())->save();
       }
 
       // Delete the field itself if we just deleted its last instance.
-      if ($field_cleanup && count($this->field_config->getBundles()) == 0) {
-        $this->field_config->delete();
+      if ($field_cleanup && count($this->fieldConfig->getBundles()) == 0) {
+        $this->fieldConfig->delete();
       }
     }
   }
@@ -487,29 +487,29 @@ public function delete($field_cleanup = TRUE) {
   /**
    * {@inheritdoc}
    */
-  public function getField() {
-    return $this->field_config;
+  public function getFieldConfig() {
+    return $this->fieldConfig;
   }
 
   /**
    * {@inheritdoc}
    */
   public function getFieldName() {
-    return $this->field_config->id;
+    return $this->fieldConfig->id;
   }
 
   /**
    * {@inheritdoc}
    */
   public function getFieldType() {
-    return $this->field_config->type;
+    return $this->fieldConfig->type;
   }
 
   /**
    * {@inheritdoc}
    */
   public function getFieldSettings() {
-    return $this->settings + $this->field_config->getFieldSettings();
+    return $this->settings + $this->fieldConfig->getFieldSettings();
   }
 
   /**
@@ -520,7 +520,7 @@ public function getFieldSetting($setting_name) {
       return $this->settings[$setting_name];
     }
     else {
-      return $this->field_config->getFieldSetting($setting_name);
+      return $this->fieldConfig->getFieldSetting($setting_name);
     }
   }
 
@@ -528,7 +528,7 @@ public function getFieldSetting($setting_name) {
    * {@inheritdoc}
    */
   public function getFieldPropertyNames() {
-    $schema = $this->field_config->getSchema();
+    $schema = $this->fieldConfig->getSchema();
     return array_keys($schema['columns']);
   }
 
@@ -536,7 +536,7 @@ public function getFieldPropertyNames() {
    * {@inheritdoc}
    */
   public function isFieldTranslatable() {
-    return $this->field_config->translatable;
+    return $this->fieldConfig->translatable;
   }
 
   /**
@@ -557,7 +557,7 @@ public function getFieldDescription() {
    * {@inheritdoc}
    */
   public function getFieldCardinality() {
-    return $this->field_config->cardinality;
+    return $this->fieldConfig->cardinality;
   }
 
   /**
@@ -589,7 +589,7 @@ public function &offsetGet($offset) {
       return $this->field_uuid;
     }
     if ($offset == 'field_name') {
-      return $this->field_config->id;
+      return $this->fieldConfig->id;
     }
     return $this->{$offset};
   }
diff --git a/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php b/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
index e7775ad..6542b9c 100644
--- a/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
@@ -196,7 +196,7 @@ function testImageFieldSettings() {
       $field_name . '[' . Language::LANGCODE_NOT_SPECIFIED . '][0][title]' => $this->randomName($test_size),
     );
     $this->drupalPost('node/' . $nid . '/edit', $edit, t('Save and keep published'));
-    $schema = $instance->getField()->getSchema();
+    $schema = $instance->getFieldConfig()->getSchema();
     $this->assertRaw(t('Alternate text cannot be longer than %max characters but is currently %length characters long.', array(
       '%max' => $schema['columns']['alt']['length'],
       '%length' => $test_size,
diff --git a/core/modules/image/lib/Drupal/image/Tests/ImageFieldTestBase.php b/core/modules/image/lib/Drupal/image/Tests/ImageFieldTestBase.php
index f59585b..83dd691 100644
--- a/core/modules/image/lib/Drupal/image/Tests/ImageFieldTestBase.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageFieldTestBase.php
@@ -67,6 +67,8 @@ function setUp() {
    *   A list of instance settings that will be added to the instance defaults.
    * @param $widget_settings
    *   A list of widget settings that will be added to the widget defaults.
+   *
+   * @return \Drupal\field\Plugin\Core\Entity\FieldInstanceConfig
    */
   function createImageField($name, $type_name, $field_settings = array(), $instance_settings = array(), $widget_settings = array()) {
     $field = array(
@@ -103,7 +105,6 @@ function createImageField($name, $type_name, $field_settings = array(), $instanc
       ->save();
 
     return $field_instance_config;
-
   }
 
   /**