`with` is deprecated, but there is still a bunch of legacy code that uses it.

This code works fine in Firefox and Chrome but throws "Can't find variable: foo" in Safari:

```js
let obj = {foo:"bar"};
with(obj) {
  function test() {
    console.log(foo);
  }
}
test();
```

Perchance.org, for example, uses `with` as part of its DSL, and so a subset of 'generators' are broken for Safari users.

Possibly related: https://bugs.webkit.org/show_bug.cgi?id=231166