Issue #3317652 by mondrake, longwave: Fix Updater PHPStan L0 issues

(cherry picked from commit d96c99b4)

core/lib/Drupal/Core/Updater/Updater.php

@@ -8,7 +8,7 @@
 /**
  * Defines the base class for Updaters used in Drupal.
  */
-class Updater {
+abstract class Updater {
 
   /**
    * Directory to install from.
@@ -194,6 +194,14 @@ public static function getProjectTitle($directory) {
     return $info['name'];
   }
 
+  /**
+   * Returns the path to the default install location for the current project.
+   *
+   * @return string
+   *   The absolute path of the directory.
+   */
+  abstract public function getInstallDirectory();
+
   /**
    * Stores the default parameters for the Updater.
    *

core/phpstan-baseline.neon

@@ -395,11 +395,6 @@ parameters:
 			count: 1
 			path: lib/Drupal/Core/Updater/Module.php
 
-		-
-			message: "#^Call to an undefined method Drupal\\\\Core\\\\Updater\\\\Updater\\:\\:getInstallDirectory\\(\\)\\.$#"
-			count: 1
-			path: lib/Drupal/Core/Updater/Updater.php
-
 		-
 			message: "#^Method Drupal\\\\action\\\\Form\\\\ActionFormBase\\:\\:save\\(\\) should return int but return statement is missing\\.$#"
 			count: 1