Strict null check serviceMock

src/tsconfig.strictNullChecks.json

@@ -445,6 +445,7 @@
 		"./vs/platform/instantiation/common/instantiationService.ts",
 		"./vs/platform/instantiation/common/serviceCollection.ts",
 		"./vs/platform/instantiation/node/instantiationService.ts",
+		"./vs/platform/instantiation/test/common/instantiationServiceMock.ts",
 		"./vs/platform/integrity/common/integrity.ts",
 		"./vs/platform/integrity/node/integrityServiceImpl.ts",
 		"./vs/platform/issue/common/issue.ts",

src/vs/platform/instantiation/test/common/instantiationServiceMock.ts

@@ -37,12 +37,12 @@ export class TestInstantiationService extends InstantiationService {
 		return <T>this._create(service, { mock: true });
 	}
 
-	public stub<T>(service?: ServiceIdentifier<T>, ctor?: any): T;
-	public stub<T>(service?: ServiceIdentifier<T>, obj?: any): T;
-	public stub<T>(service?: ServiceIdentifier<T>, ctor?: any, property?: string, value?: any): sinon.SinonStub;
-	public stub<T>(service?: ServiceIdentifier<T>, obj?: any, property?: string, value?: any): sinon.SinonStub;
-	public stub<T>(service?: ServiceIdentifier<T>, property?: string, value?: any): sinon.SinonStub;
-	public stub<T>(serviceIdentifier?: ServiceIdentifier<T>, arg2?: any, arg3?: string, arg4?: any): sinon.SinonStub {
+	public stub<T>(service: ServiceIdentifier<T>, ctor?: any): T;
+	public stub<T>(service: ServiceIdentifier<T>, obj?: any): T;
+	public stub<T>(service: ServiceIdentifier<T>, ctor?: any, property?: string, value?: any): sinon.SinonStub;
+	public stub<T>(service: ServiceIdentifier<T>, obj?: any, property?: string, value?: any): sinon.SinonStub;
+	public stub<T>(service: ServiceIdentifier<T>, property?: string, value?: any): sinon.SinonStub;
+	public stub<T>(serviceIdentifier: ServiceIdentifier<T>, arg2?: any, arg3?: string, arg4?: any): sinon.SinonStub {
 		let service = typeof arg2 !== 'string' ? arg2 : void 0;
 		let serviceMock: IServiceMock<any> = { id: serviceIdentifier, service: service };
 		let property = typeof arg2 === 'string' ? arg2 : arg3;