When the rest parameter shared the same name as a default identifier
for a param, the loop would be hoisted outside the function!
```js
var a = 1;
for (var _len = arguments.length, a = Array(_len > 1 ? _len - 1 : 0),
_key = 1; _key < _len; _key++) {
a[_key - 1] = arguments[_key];
}
function foo2() {
var b = arguments.length <= 0 || arguments[0] === undefined ? a :
arguments[0];
assert.equal(b, 1);
}
foo2(undefined, 2);
```
And if you tried to reference any index or `#length`, it’d blow up and
refuse to transpile.
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