Let's write this out without magic:

```js
var type = this.type;
return json.map(function(data) {
  return type.parse(data);
});
```
or
```js
return json.map(function(data) { return this.type.parse(data); }, this);
```
That suggests that the context for `this.type.parse` should be `this.type` (e.g. `Person`), not `this` (e.g. `PersonCollection`).