fix: do not allow non constructor calls

Author: medikoo

array.js

@@ -8,7 +8,7 @@ var setPrototypeOf = require("es5-ext/object/set-prototype-of")
 var defineProperty = Object.defineProperty, ArrayIterator;
 
 ArrayIterator = module.exports = function (arr, kind) {
-	if (!(this instanceof ArrayIterator)) return new ArrayIterator(arr, kind);
+	if (!(this instanceof ArrayIterator)) throw new TypeError("Constructor requires 'new'");
 	Iterator.call(this, arr);
 	if (!kind) kind = "value";
 	else if (contains.call(kind, "key+value")) kind = "key+value";

index.js

@@ -11,7 +11,7 @@ var clear    = require("es5-ext/array/#/clear")
 var defineProperty = Object.defineProperty, defineProperties = Object.defineProperties, Iterator;
 
 module.exports = Iterator = function (list, context) {
-	if (!(this instanceof Iterator)) return new Iterator(list, context);
+	if (!(this instanceof Iterator)) throw new TypeError("Constructor requires 'new'");
 	defineProperties(this, {
 		__list__: d("w", value(list)),
 		__context__: d("w", context),

string.js

@@ -10,7 +10,7 @@ var setPrototypeOf = require("es5-ext/object/set-prototype-of")
 var defineProperty = Object.defineProperty, StringIterator;
 
 StringIterator = module.exports = function (str) {
-	if (!(this instanceof StringIterator)) return new StringIterator(str);
+	if (!(this instanceof StringIterator)) throw new TypeError("Constructor requires 'new'");
 	str = String(str);
 	Iterator.call(this, str);
 	defineProperty(this, "__length__", d("", str.length));