Jest: Added Generic for "toMatchObject" function (#35033)

* Add generic to toMatchObject

* Cover feedback from @wsmd

types/jest/index.d.ts

@@ -18,6 +18,7 @@
 //                 Sebastian Sebald <https://github.com/sebald>
 //                 Andy <https://github.com/andys8>
 //                 Antoine Brault <https://github.com/antoinebrault>
+//                 Jeroen Claassens <https://github.com/favna>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 3.0
 
@@ -757,8 +758,25 @@ declare namespace jest {
         toMatch(expected: string | RegExp): R;
         /**
          * Used to check that a JavaScript object matches a subset of the properties of an object
+         *
+         * Optionally, you can provide an object to use as Generic type for the expected value.
+         * This ensures that the matching object matches the structure of the provided object-like type.
+         *
+         * @example
+         *
+         * type House = {
+         *   bath: boolean;
+         *   bedrooms: number;
+         *   kitchen: {
+         *     amenities: string[];
+         *     area: number;
+         *     wallColor: string;
+         *   }
+         * };
+         *
+         * expect(desiredHouse).toMatchObject<House>(...standardHouse, kitchen: {area: 20}) // wherein standardHouse is some base object of type House
          */
-        toMatchObject(expected: {} | any[]): R;
+        toMatchObject<E extends {} | any[]>(expected: E): R;
         /**
          * This ensures that a value matches the most recent snapshot with property matchers.
          * Check out [the Snapshot Testing guide](http://facebook.github.io/jest/docs/snapshot-testing.html) for more information.

types/jest/jest-tests.ts

@@ -830,6 +830,8 @@ describe("", () => {
         expect({ abc: "def" }).toMatchObject({ abc: "def" });
         expect({}).toMatchObject([{}, {}]);
         expect({ abc: "def" }).toMatchObject([{ abc: "def" }, { invalid: "property" }]);
+        expect({abc: "def"}).toMatchObject<{abc: string}>({abc: "def"});
+        expect([{abc: 'def'}, {abc: 'def'}]).toMatchObject<[{abc: string}, {abc: string}]>([{abc: 'def'}, {abc: 'def'}]);
 
         expect({}).toMatchSnapshot();
         expect({}).toMatchSnapshot("snapshotName");