add an extra regression test case for string completions

Author: Andarist

tests/cases/fourslash/arityErrorAfterStringCompletions.ts

@@ -0,0 +1,14 @@
+///<reference path="fourslash.ts"/>
+// @strict: true
+////
+//// interface Events {
+////   click: any;
+////   drag: any;
+//// }
+////
+//// declare function addListener<K extends keyof Events>(type: K, listener: (ev: Events[K]) => any): void;
+////
+//// /*1*/addListener("/*2*/")/*3*/
+
+verify.completions({ marker: ["2"], exact: ["click", "drag"] });
+verify.errorExistsBetweenMarkers("1", "3");