Revert "Downgrade code to be PHP 7.0 compliant."

This reverts commit edb2b85.

This partially reverts some code that was done long ago to
keep compatibility with PHP 7.0.

As far as moodle-cs now only supports PHP 7.4 and up, we
can move back to use return types.

Fixes moodlehq#107

moodle/Util/MoodleUtil.php

@@ -102,7 +102,7 @@ protected static function loadCoreComponent(string $moodleRoot): bool {
      * @param string $moodleRoot Full path to a valid moodle.root
      * @return array Associative array of components as keys and paths as values or null if not found.
      */
-    protected static function calculateAllComponents(string $moodleRoot) {
+    protected static function calculateAllComponents(string $moodleRoot): ?array {
         // If we have calculated the components already, straight return them.
         if (!empty(self::$moodleComponents)) {
             return self::$moodleComponents;
@@ -205,6 +205,7 @@ protected static function calculateAllComponents(string $moodleRoot) {
      *
      * @return string|null a valid moodle component for the file or null if not found.
      */
+    public static function getMoodleComponent(File $file, $selfPath = true): ?string {
     public static function getMoodleComponent(File $file, $selfPath = true) {
         if (defined('PHPUNIT_TEST') && PHPUNIT_TEST && !empty(self::$mockedComponentMappings)) {
             $components = self::$mockedComponentMappings; // @codeCoverageIgnore
@@ -252,7 +253,7 @@ public static function getMoodleComponent(File $file, $selfPath = true) {
      *
      * @return int|null the numeric branch in moodle root version.php or null if not found
      */
-    public static function getMoodleBranch(File $file = null, bool $selfPath = true) {
+    public static function getMoodleBranch(?File $file = null, bool $selfPath = true): ?int {
 
         // Return already calculated value if available.
         if (self::$moodleBranch !== false) {
@@ -270,7 +271,7 @@ public static function getMoodleBranch(File $file = null, bool $selfPath = true)
                 throw new DeepExitException(
                     "ERROR: Incorrect 'moodleBranch' config/runtime option. Value must be 4 digit max.: '$branch'", 3);
             }
-            self::$moodleBranch = (int)$branch;
+            self::$moodleBranch = $branch;
             return self::$moodleBranch;
         }
 
@@ -288,7 +289,7 @@ public static function getMoodleBranch(File $file = null, bool $selfPath = true)
                 // Find the $branch value.
                 if ($valueToken = $versionFile->findNext(T_CONSTANT_ENCAPSED_STRING, $varToken)) {
                     $branch = trim($versionFile->getTokens()[$valueToken]['content'], "\"'");
-                    self::$moodleBranch = (int)$branch;
+                    self::$moodleBranch = $branch;
                     return self::$moodleBranch;
                 }
             }
@@ -313,7 +314,7 @@ public static function getMoodleBranch(File $file = null, bool $selfPath = true)
      *
      * @return string|null the full path to moodle root or null if not found.
      */
-    public static function getMoodleRoot(File $file = null, bool $selfPath = true) {
+    public static function getMoodleRoot(?File $file = null, bool $selfPath = true): ?string {
         // Return already calculated value if available.
         if (self::$moodleRoot !== false) {
             return self::$moodleRoot;