Fix type assumptions about Connection::lastInsertId()

src/Connection.php

@@ -878,8 +878,6 @@ public function getTransactionNestingLevel(): int
      *
      * If the underlying driver does not support identity columns, an exception is thrown.
      *
-     * @return int|string The last insert ID, as an integer or a numeric string.
-     *
      * @throws Exception
      */
     public function lastInsertId(): int|string

src/Driver/Connection.php

@@ -46,18 +46,16 @@ public function exec(string $sql): int|string;
     /**
      * Returns the ID of the last inserted row.
      *
-     * This method returns an integer or a numeric string representing the value of the auto-increment column
+     * This method returns an integer or a string representing the value of the auto-increment column
      * from the last row inserted into the database, if any, or throws an exception if a value cannot be returned,
      * in particular when:
      *
      * - the driver does not support identity columns;
      * - the last statement dit not return an identity (caution: see note below).
      *
      * Note: if the last statement was not an INSERT to an autoincrement column, this method MAY return an ID from a
-     * previous statement. DO NOT RELY ON THIS BEHAVIOR which is driver-dependent: always use getLastInsertId() right
-     * after executing an INSERT statement.
-     *
-     * @return int|string The last insert ID, as an integer or a numeric string.
+     * previous statement. DO NOT RELY ON THIS BEHAVIOR which is driver-dependent: always call this method right after
+     * executing an INSERT statement.
      *
      * @throws Exception
      */

src/Driver/IBMDB2/Connection.php

@@ -77,7 +77,7 @@ public function exec(string $sql): int|string
         return db2_num_rows($stmt);
     }
 
-    public function lastInsertId(): int|string
+    public function lastInsertId(): string
     {
         $lastInsertId = db2_last_insert_id($this->connection);