Fixed some issues detected by PHPstan.

src/Entity/Parts/PartLot.php

@@ -233,7 +233,7 @@ class PartLot extends DBElement
     /**
      * Sets the part that is stored in this part lot.
      *
-     * @param Part|InstockTrait $part
+     * @param Part $part
      *
      * @return PartLot
      */

src/Entity/Parts/PartTraits/OrderTrait.php

@@ -126,6 +126,7 @@ trait OrderTrait
      * The orderdetail is assigned to this part.
      *
      * @param Orderdetail $orderdetail the orderdetail that should be added
+     * @return $this
      */
     public function addOrderdetail(Orderdetail $orderdetail): self
     {
@@ -137,8 +138,8 @@ trait OrderTrait
 
     /**
      * Removes the given orderdetail from the list of orderdetails.
-     *
-     * @return OrderTrait
+     * @param Orderdetail $orderdetail
+     * @return $this
      */
     public function removeOrderdetail(Orderdetail $orderdetail): self
     {
@@ -158,6 +159,7 @@ trait OrderTrait
      *                                                (if the part has exactly one orderdetails,
      *                                                set this orderdetails as order orderdetails.
      *                                                Otherwise, set "no order orderdetails")
+     * @return $this
      */
     public function setManualOrder(bool $new_manual_order, int $new_order_quantity = 1, ?Orderdetail $new_order_orderdetail = null): self
     {