Issue #2567767 by Antti J. Salminen: Remove unused function _system_is_incompatible from core

core/modules/system/system.admin.inc

@@ -13,33 +13,6 @@
 use Drupal\Core\Render\Element;
 use Drupal\Core\Template\Attribute;
 
-/**
- * Recursively check compatibility.
- *
- * @param $incompatible
- *   An associative array which at the end of the check contains all
- *   incompatible files as the keys, their values being TRUE.
- * @param $files
- *   The set of files that will be tested.
- * @param \Drupal\Core\Extension\Extension $file
- *   The file at which the check starts.
- * @return
- *   Returns TRUE if an incompatible file is found, NULL (no return value)
- *   otherwise.
- */
-function _system_is_incompatible(&$incompatible, $files, Extension $file) {
-  if (isset($incompatible[$file->getName()])) {
-    return TRUE;
-  }
-  // Recursively traverse required modules, looking for incompatible modules.
-  foreach ($file->requires as $requires) {
-    if (isset($files[$requires]) && _system_is_incompatible($incompatible, $files, $files[$requires])) {
-      $incompatible[$file->getName()] = TRUE;
-      return TRUE;
-    }
-  }
-}
-
 /**
  * Prepares variables for administrative content block templates.
  *