Added shortcut in checkAwaitedType for isolatedModules

tests/cases/conformance/async/es6/asyncAwaitIsolatedModules_es6.ts

@@ -0,0 +1,41 @@
+// @target: ES6
+// @isolatedModules: true
+import { MyPromise } from "missing";
+
+declare var p: Promise<number>;
+declare var mp: MyPromise<number>;
+
+async function f0() { }
+async function f1(): Promise<void> { }
+async function f3(): MyPromise<void> { }
+
+let f4 = async function() { }
+let f5 = async function(): Promise<void> { }
+let f6 = async function(): MyPromise<void> { }
+
+let f7 = async () => { };
+let f8 = async (): Promise<void> => { };
+let f9 = async (): MyPromise<void> => { }; 
+let f10 = async () => p;
+let f11 = async () => mp;
+let f12 = async (): Promise<number> => mp;
+let f13 = async (): MyPromise<number> => p;
+
+let o = {
+	async m1() { },
+	async m2(): Promise<void> { },
+	async m3(): MyPromise<void> { }
+};
+
+class C {
+	async m1() { }
+	async m2(): Promise<void> { }
+	async m3(): MyPromise<void> { }
+	static async m4() { }
+	static async m5(): Promise<void> { }
+	static async m6(): MyPromise<void> { }
+}
+
+module M {
+	export async function f1() { }
+}