Add completion test for partial generic object (#34559)

tests/cases/fourslash/completionsWithOptionalPropertiesGenericValidBoolean.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+// @strict: true
+
+//// interface MyOptions {
+////     hello?: boolean;
+////     world?: boolean;
+//// }
+//// declare function bar<T extends MyOptions>(options?: Partial<T>): void;
+//// bar({ hello: true, /*1*/ });
+
+verify.completions({
+  marker: '1',
+  includes: [
+    {
+      sortText: completion.SortText.OptionalMember,
+      name: 'world'
+    },
+  ]
+})