Issue #3463447 by acbramley: Fix diff 2.x integration

src/Plugin/diff/Field/SmartdateFieldBuilder.php

@@ -26,7 +26,7 @@ class SmartdateFieldBuilder extends FieldDiffBuilderBase {
   /**
    * {@inheritdoc}
    */
-  public function build(FieldItemListInterface $field_items) {
+  public function build(FieldItemListInterface $field_items): mixed {
     $result = [];
 
     $format = \Drupal::entityTypeManager()
@@ -60,7 +60,7 @@ class SmartdateFieldBuilder extends FieldDiffBuilderBase {
   /**
    * {@inheritdoc}
    */
-  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state): array {
     unset($form['format_type']);
 
     // Change the description of the timezone_override element.
@@ -96,7 +96,7 @@ class SmartdateFieldBuilder extends FieldDiffBuilderBase {
   /**
    * {@inheritdoc}
    */
-  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+  public function submitConfigurationForm(array &$form, FormStateInterface $form_state): void {
     $this->configuration['timezone_override'] = $form_state->getValue('timezone_override');
     $this->configuration['format'] = $form_state->getValue('format');
 
@@ -106,7 +106,7 @@ class SmartdateFieldBuilder extends FieldDiffBuilderBase {
   /**
    * {@inheritdoc}
    */
-  public function defaultConfiguration() {
+  public function defaultConfiguration(): array {
     $default_configuration = [
       'timezone_override' => 0,
       'format' => 'default',