Issue #3221798 by larowlan, pradhumanjain2311, alexpott, tim.plunkett, tunic,...

Issue #3221798 by larowlan, pradhumanjain2311, alexpott, tim.plunkett, tunic, Eric_A, longwave, FatherShawn: Remove stale processing and reference to form_type_TYPE_value

core/lib/Drupal/Core/Form/FormBuilder.php

@@ -1232,10 +1232,7 @@ protected function handleInputElement($form_id, &$element, FormStateInterface &$
 
     // Set the element's #value property.
     if (!isset($element['#value']) && !array_key_exists('#value', $element)) {
-      // @todo Once all elements are converted to plugins in
-      //   https://www.drupal.org/node/2311393, rely on
-      //   $element['#value_callback'] directly.
-      $value_callable = !empty($element['#value_callback']) ? $element['#value_callback'] : 'form_type_' . $element['#type'] . '_value';
+      $value_callable = $element['#value_callback'] ?? NULL;
       if (!is_callable($value_callable)) {
         $value_callable = '\Drupal\Core\Render\Element\FormElement::valueCallback';
       }

core/lib/Drupal/Core/Form/FormBuilderInterface.php

@@ -257,8 +257,7 @@ public function prepareForm($form_id, &$form, FormStateInterface &$form_state);
    * customize what happens. For example, during this function's life cycle,
    * the following functions get called for each element:
    * - $element['#value_callback']: A callable that implements how user input is
-   *   mapped to an element's #value property. This defaults to a function named
-   *   'form_type_TYPE_value' where TYPE is $element['#type'].
+   *   mapped to an element's #value property.
    * - $element['#process']: An array of functions called after user input has
    *   been mapped to the element's #value property. These functions can be used
    *   to dynamically add child elements: for example, for the 'date' element