MDL-80820 various: fix incorrect phpdocs

lib/accesslib.php

@@ -383,7 +383,7 @@ function get_role_definitions_uncached(array $roleids) {
  * Get the default guest role, this is used for guest account,
  * search engine spiders, etc.
  *
- * @return stdClass role record
+ * @return stdClass|false role record
  */
 function get_guest_role() {
     global $CFG, $DB;
@@ -970,7 +970,7 @@ function get_empty_accessdata() {
  * @access private
  * @param int $userid
  * @param bool $preloadonly true means do not return access array
- * @return array accessdata
+ * @return ?array accessdata
  */
 function get_user_accessdata($userid, $preloadonly=false) {
     global $CFG, $ACCESSLIB_PRIVATE, $USER;
@@ -2587,7 +2587,7 @@ function is_inside_frontpage(context $context) {
  * Returns capability information (cached)
  *
  * @param string $capabilityname
- * @return stdClass or null if capability not found
+ * @return ?stdClass object or null if capability not found
  */
 function get_capability_info($capabilityname) {
     $caps = get_all_capabilities();
@@ -2619,7 +2619,7 @@ function get_capability_info($capabilityname) {
  * Do not use this function except in the get_capability_info
  *
  * @param string $capabilityname
- * @return stdClass|null with deprecation message and potential replacement if not null
+ * @return array|null with deprecation message and potential replacement if not null
  */
 function get_deprecated_capability_info($capabilityname) {
     $cache = cache::make('core', 'capabilities');