Added test.

tests/cases/fourslash/completionListInObjectLiteral4.ts

@@ -0,0 +1,28 @@
+/// <reference path='fourslash.ts'/>
+
+// @strictNullChecks: true
+////interface Thing {
+////    hello: number;
+////    world: string;
+////}
+////
+////declare function funcA(x : Thing): void;
+////declare function funcB(x?: Thing): void;
+////declare function funcC(x : Thing | null): void;
+////declare function funcD(x : Thing | undefined): void;
+////declare function funcE(x : Thing | null | undefined): void;
+////declare function funcF(x?: Thing | null | undefined): void;
+////
+////funcA({ /*A*/ });
+////funcB({ /*B*/ });
+////funcC({ /*C*/ });
+////funcD({ /*D*/ });
+////funcE({ /*E*/ });
+////funcF({ /*F*/ });
+
+
+for (const marker of test.markers()) {
+    goTo.position(marker.position);
+    verify.completionListContains("hello");
+    verify.completionListContains("world");
+}