Add test

tests/cases/conformance/expressions/typeGuards/typeGuardOfFormFunctionEquality.ts

@@ -0,0 +1,14 @@
+declare function isString1(a: number, b: Object): b is string;
+
+declare function isString2(a: Object): a is string;
+
+switch (isString1(0, "")) {
+    case isString2(""):
+    default:
+}
+
+var x = isString1(0, "") === isString2("");
+
+function isString3(a: number, b: number, c: Object): c is string {
+    return isString1(0, c);
+}