docs: fix types in doc comments

Author: kenjis

system/Database/BaseConnection.php

@@ -33,7 +33,7 @@
  * @property mixed      $encrypt
  * @property array      $failover
  * @property string     $hostname
- * @property mixed      $lastQuery
+ * @property Query      $lastQuery
  * @property string     $password
  * @property bool       $pConnect
  * @property int|string $port
@@ -154,7 +154,7 @@ abstract class BaseConnection implements ConnectionInterface
     /**
      * Encryption flag/data
      *
-     * @var mixed
+     * @var array|bool
      */
     protected $encrypt = false;
 
@@ -185,7 +185,7 @@ abstract class BaseConnection implements ConnectionInterface
      * The last query object that was executed
      * on this connection.
      *
-     * @var mixed
+     * @var Query
      */
     protected $lastQuery;
 
@@ -932,7 +932,7 @@ public function prepare(Closure $func, array $options = [])
     /**
      * Returns the last query's statement object.
      *
-     * @return mixed
+     * @return Query
      */
     public function getLastQuery()
     {
@@ -1149,9 +1149,10 @@ private function protectDotItem(string $item, string $alias, bool $protectIdenti
      *
      * This function escapes column and table names
      *
-     * @param mixed $item
+     * @param array|string $item
      *
-     * @return mixed
+     * @return array|string
+     * @phpstan-return ($item is array ? array : string)
      */
     public function escapeIdentifiers($item)
     {