diff --git a/core/modules/field/src/Entity/FieldConfig.php b/core/modules/field/src/Entity/FieldConfig.php
index a50d92f..e56aa06 100644
--- a/core/modules/field/src/Entity/FieldConfig.php
+++ b/core/modules/field/src/Entity/FieldConfig.php
@@ -469,7 +469,7 @@ public function getSchema() {
 
       // Merge custom indexes with those specified by the field type. Custom
       // indexes prevail.
-      $schema['indexes'] = $this->getIndexes() + $schema['indexes'];
+      $schema['indexes'] = $this->indexes + $schema['indexes'];
 
       $this->schema = $schema;
     }
@@ -520,12 +520,7 @@ public function getName() {
   }
 
   /**
-   * Sets the field config indexes.
-   *
-   * @param array $indexes
-   *   The field config indexes.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setIndexes(array $indexes) {
     $this->set('indexes', $indexes);
@@ -533,22 +528,7 @@ public function setIndexes(array $indexes) {
   }
 
   /**
-   * Returns the indexes array of the field config.
-   *
-   * @return array
-   *   The indexes array.
-   */
-  public function getIndexes() {
-    return $this->indexes;
-  }
-
-  /**
-   * Sets the field config deleted property.
-   *
-   * @param bool $deleted
-   *   The field config deleted property.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setDeleted($deleted) {
     $this->set('deleted', $deleted);
@@ -556,20 +536,14 @@ public function setDeleted($deleted) {
   }
 
   /**
-   * Returns the deleted property of the field config.
-   *
-   * @return bool
-   *   The deleted property.
+   * {@inheritdoc}
    */
   public function isDeleted() {
     return $this->deleted;
   }
 
   /**
-   * Returns the name of the module providing the field type.
-   *
-   * @return string
-   *   The name of the module that provides the field type.
+   * {@inheritdoc}
    */
   public function getModule() {
     return $this->module;
@@ -616,14 +590,7 @@ public function getSetting($setting_name) {
   }
 
   /**
-   * Sets the value for a field setting.
-   *
-   * @param string $setting_name
-   *   The name of the setting.
-   * @param mixed $value
-   *   The value of the setting.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setSetting($setting_name, $value) {
     $this->settings[$setting_name] = $value;
@@ -631,12 +598,7 @@ public function setSetting($setting_name, $value) {
   }
 
   /**
-   * Sets field settings.
-   *
-   * @param string $settings
-   *   The array of field settings.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setSettings($settings) {
     $this->set('settings', $settings);
@@ -659,12 +621,7 @@ public function isRevisionable() {
   }
 
   /**
-   * Sets whether the field is translatable.
-   *
-   * @param bool $translatable
-   *   Whether the field is translatable.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setTranslatable($translatable) {
     $this->translatable = $translatable;
@@ -700,12 +657,7 @@ public function getCardinality() {
   }
 
   /**
-   * Sets the maximum number of items allowed for the field.
-   *
-   * @param integer $cardinality
-   *   The cardinality value.
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setCardinality($cardinality) {
     $this->set('cardinality', $cardinality);
@@ -735,12 +687,7 @@ public function isLocked() {
   }
 
   /**
-   * Sets the locked flag.
-   *
-   * @param bool $locked
-   *   Sets value of locked flag
-   *
-   * @return $this
+   * {@inheritdoc}
    */
   public function setLocked($locked) {
     $this->set('locked', $locked);
@@ -748,19 +695,6 @@ public function setLocked($locked) {
   }
 
   /**
-   * Sets the entity type of the field config.
-   *
-   * @param string $entity_type
-   *   The entity type.
-   *
-   * @return $this
-   */
-  public function setTargetEntityTypeId($entity_type) {
-    $this->set('entity_type', $entity_type);
-    return $this;
-  }
-
-  /**
    * {@inheritdoc}
    */
   public function getTargetEntityTypeId() {
diff --git a/core/modules/field/src/FieldConfigInterface.php b/core/modules/field/src/FieldConfigInterface.php
index c6575ec..e302531 100644
--- a/core/modules/field/src/FieldConfigInterface.php
+++ b/core/modules/field/src/FieldConfigInterface.php
@@ -31,4 +31,92 @@ public function getBundles();
    */
   public function isLocked();
 
+  /**
+   * Sets the locked flag.
+   *
+   * @param bool $locked
+   *   Sets value of locked flag
+   *
+   * @return $this
+   */
+  public function setLocked($locked);
+
+  /**
+   * Returns whether the field is deleted or not.
+   *
+   * @return bool
+   *   The deleted property.
+   */
+  public function isDeleted();
+
+  /**
+   * Sets the field config deleted property.
+   *
+   * @param bool $deleted
+   *   The field config deleted property.
+   *
+   * @return $this
+   */
+  public function setDeleted($deleted);
+
+/**
+   * Sets the maximum number of items allowed for the field.
+   *
+   * @param integer $cardinality
+   *   The cardinality value.
+   *
+   * @return $this
+   */
+  public function setCardinality($cardinality);
+
+  /**
+   * Sets the field config indexes.
+   *
+   * @param array $indexes
+   *   The field config indexes.
+   *
+   * @return $this
+   */
+  public function setIndexes(array $indexes);
+
+  /**
+   * Sets the value for a field setting by name.
+   *
+   * @param string $setting_name
+   *   The name of the setting.
+   * @param mixed $value
+   *   The value of the setting.
+   *
+   * @return $this
+   */
+  public function setSetting($setting_name, $value);
+
+/**
+   * Sets field settings by overwriting the settings array.
+   *
+   * @param string $settings
+   *   The array of field settings.
+   *
+   * @return $this
+   */
+  public function setSettings($settings);
+
+  /**
+   * Returns the name of the module providing the field type.
+   *
+   * @return string
+   *   The name of the module that provides the field type.
+   */
+  public function getModule();
+
+  /**
+   * Sets whether the field is translatable.
+   *
+   * @param bool $translatable
+   *   Whether the field is translatable.
+   *
+   * @return $this
+   */
+  public function setTranslatable($translatable);
+
 }