Add a skipped test for a Number caveat when [[Call]]ed with a `Nu…

…mber` instance as the receiver.

Closes #365.

README.md

@@ -214,8 +214,14 @@ Promise.resolve(5).then(function (value) {
 
 ## Caveats
 
-- `Object.setPrototypeOf` / `Reflect.setPrototypeOf`
+ - `Object.setPrototypeOf` / `Reflect.setPrototypeOf`
    - Note that null objects (`Object.create(null)`, eg, an object with `null` as its `[[Prototype]]`) can not have their `[[Prototype]]` changed except via a native `Object.setPrototypeOf`.
+ - `Number`:
+   - In order to support binary literals (`Number('0b1')`) and octal literals (`Number('0o7')`), the global `Number` constructor is wrapped in a shim. However, this can cause issues in the exceedingly unlikely event that you ever call `Number` as a function with a receiver (a “this” value) that is itself a number. Some problematic examples:
+```js
+  assert(typeof Number.call(2, 3) === 'number'); // will fail when `Number` is wrapped, is "object"
+  assert(typeof (1).constructor(2) === 'number'); // will fail when `Number` is wrapped, is "object"
+```
 
 ## [License][license-url]
 

test/number.js

@@ -1,4 +1,4 @@
-/* global describe, it, expect, require */
+/* global describe, it, xit, expect, require */
 
 describe('Number', function () {
   var functionsHaveNames = (function foo() {}).name === 'foo';
@@ -338,6 +338,13 @@ describe('Number', function () {
       expect((1).constructor).to.equal(Number);
     });
 
+    xit('returns a primitive when called with a receiver', function () {
+      expect((1).constructor(2)).to.equal(2);
+      expect(Object(1).constructor(3)).to.equal(3);
+      expect(Object(1).constructor.apply(null, 4)).to.equal(4);
+      expect(Object(1).constructor.apply(Object(1).constructor, 5)).to.equal(5);
+    });
+
     it('works with boxed primitives', function () {
       expect(1 instanceof Number).to.equal(false);
       expect(Object(1) instanceof Number).to.equal(true);