Issue #2877828 by msankhala, joachim: FormInterface::getFormId() should state...

Issue #2877828 by msankhala, joachim: FormInterface::getFormId() should state restrictions on the returned ID string

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

@@ -12,6 +12,10 @@ interface FormInterface {
   /**
    * Returns a unique string identifying the form.
    *
+   * The returned ID should be a unique string that can be a valid PHP function
+   * name, since it's used in hook implementation names such as
+   * hook_form_FORM_ID_alter().
+   *
    * @return string
    *   The unique string identifying the form.
    */