diff -u b/core/modules/field/field.api.php b/core/modules/field/field.api.php
--- b/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -2139,7 +2139,7 @@
  *
  * @param $op
  *   The operation to be performed. Possible values: 'edit', 'view'.
- * @param $field
+ * @param \Drupal\field\FieldInterface $field
  *   The field on which the operation is to be performed.
  * @param $entity_type
  *   The type of $entity; for example, 'node' or 'user'.
@@ -2151,7 +2151,7 @@
  * @return
  *   TRUE if the operation is allowed, and FALSE if the operation is denied.
  */
-function hook_field_access($op, $field, $entity_type, $entity, $account) {
+function hook_field_access($op, \Drupal\field\FieldInterface $field, $entity_type, $entity, $account) {
   if ($field['field_name'] == 'field_of_interest' && $op == 'edit') {
     return user_access('edit field of interest', $account);
   }
only in patch2:
unchanged:
--- a/core/modules/field/field.module
+++ b/core/modules/field/field.module
@@ -6,6 +6,7 @@
 
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Template\Attribute;
+use Drupal\field\FieldInterface;
 
 /*
  * Load all public Field API functions. Drupal currently has no
@@ -944,9 +945,8 @@ function field_has_data($field) {
  *   The operation to be performed. Possible values:
  *   - edit
  *   - view
- * @param array $field
- *   The full field structure array for the field on which the operation is to
- *   be performed. See field_info_field().
+ * @param \Drupal\field\FieldInterface $field
+ *   The field on which the operation is to be performed.
  * @param $entity_type
  *   The type of $entity; for example, 'node' or 'user'.
  * @param $entity
@@ -957,7 +957,7 @@ function field_has_data($field) {
  * @return
  *   TRUE if the operation is allowed; FALSE if the operation is denied.
  */
-function field_access($op, $field, $entity_type, $entity = NULL, $account = NULL) {
+function field_access($op, FieldInterface $field, $entity_type, $entity = NULL, $account = NULL) {
   global $user;
 
   if (!isset($account)) {
only in patch2:
unchanged:
--- a/core/modules/field/tests/modules/field_test/field_test.field.inc
+++ b/core/modules/field/tests/modules/field_test/field_test.field.inc
@@ -7,6 +7,7 @@
 
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\field\FieldException;
+use Drupal\field\FieldInterface;
 
 /**
  * Implements hook_field_info().
@@ -197,7 +198,7 @@ function field_test_default_value(EntityInterface $entity, $field, $instance) {
 /**
  * Implements hook_field_access().
  */
-function field_test_field_access($op, $field, $entity_type, $entity, $account) {
+function field_test_field_access($op, FieldInterface $field, $entity_type, $entity, $account) {
   if ($field['field_name'] == "field_no_{$op}_access") {
     return FALSE;
   }