only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Render/Element/FormElement.php
+++ b/core/lib/Drupal/Core/Render/Element/FormElement.php
@@ -50,6 +50,9 @@
  * - #field_suffix: (string) Suffix to display after the HTML input element.
  *   Should be translated, normally. If it is not already wrapped in a safe
  *   markup object, will be filtered for XSS safety.
+ * - #value: (text or numbers) A value that cannot be edited by the user.
+ * - #has_garbage_value: (bool, internal) Set to TRUE to indicate that the
+ *   #value property of an element should not be used or processed.
  * - #input: (bool, internal) Whether or not the element accepts input.
  * - #parents: (string[], read-only) Array of names of the element's parents
  *   for purposes of getting values out of $form_state. See also