Bug 1383393 - Also ignore null as Symbol.toPrimitive method. r=jandem

--HG--
extra : rebase_source : c8a11f2152d5f4c1cb7729d521cbceb43f0be37a

js/src/jsobj.cpp

@@ -3151,7 +3151,7 @@ js::ToPrimitiveSlow(JSContext* cx, JSType preferredType, MutableHandleValue vp)
         return false;
 
     // Step 6.
-    if (!method.isUndefined()) {
+    if (!method.isNullOrUndefined()) {
         // Step 6 of GetMethod. js::Call() below would do this check and throw a
         // TypeError anyway, but this produces a better error message.
         if (!IsCallable(method))

js/src/tests/ecma_6/Symbol/toPrimitive-undefined-or-null.js

@@ -0,0 +1,18 @@
+for (let method of [undefined, null]) {
+    let obj = {
+        [Symbol.toPrimitive]: method,
+        toString: () => "pass",
+    };
+    assertEq("" + obj, "pass");
+}
+
+for (let method of [true, false, 0, 123, "", "abc", Symbol(), {}]) {
+    let obj = {
+        [Symbol.toPrimitive]: method,
+        toString: () => "pass",
+    };
+    assertThrowsInstanceOf(() => "" + obj, TypeError);
+}
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);