Object.getOwnPropertyDescriptor() returns 'undefined' if property descriptor not found. (#18148)

src/lib/es2015.core.d.ts

@@ -327,7 +327,7 @@ interface ObjectConstructor {
      * @param o Object that contains the property.
      * @param p Name of the property.
      */
-    getOwnPropertyDescriptor(o: any, propertyKey: PropertyKey): PropertyDescriptor;
+    getOwnPropertyDescriptor(o: any, propertyKey: PropertyKey): PropertyDescriptor | undefined;
 
     /**
      * Adds a property to an object, or modifies attributes of an existing property.

src/lib/es2015.reflect.d.ts

@@ -4,7 +4,7 @@ declare namespace Reflect {
     function defineProperty(target: object, propertyKey: PropertyKey, attributes: PropertyDescriptor): boolean;
     function deleteProperty(target: object, propertyKey: PropertyKey): boolean;
     function get(target: object, propertyKey: PropertyKey, receiver?: any): any;
-    function getOwnPropertyDescriptor(target: object, propertyKey: PropertyKey): PropertyDescriptor;
+    function getOwnPropertyDescriptor(target: object, propertyKey: PropertyKey): PropertyDescriptor | undefined;
     function getPrototypeOf(target: object): object;
     function has(target: object, propertyKey: PropertyKey): boolean;
     function isExtensible(target: object): boolean;

src/lib/es5.d.ts

@@ -127,7 +127,7 @@ interface ObjectConstructor {
       * @param o Object that contains the property.
       * @param p Name of the property.
     */
-    getOwnPropertyDescriptor(o: any, p: string): PropertyDescriptor;
+    getOwnPropertyDescriptor(o: any, p: string): PropertyDescriptor | undefined;
 
     /**
       * Returns the names of the own properties of an object. The own properties of an object are those that are defined directly