A way to construct Functions with custom scopes?

[#!/JoePea]

For example, what if we could write something like

```js
function foo() {
  var x = 10
}

const [scope, returnValue] = scope from foo()

// can't do anything with `scope` directly, it's like an empty object
(an exotic object?).
console.log(getOwnAndInheritedKeys(scope)) // empty array

new Function('console.log(x)', { scope }) // logs 10
```

Or something.

Maybe we can pass objects, and the keys are used for scope, similar to
`with`, but they are passed by reference into the scope:

```js
new Function('console.log(x)', { scope: { x: 10 } }) // logs 10
```

I think this would open up the doors to frameworks that want to create
expressions in things like Element attributes, to make it easy for
those expression to have access to certain variables. Currently it is
difficult to make this happen; the cleanest ways of doing it involve
build steps. With this idea we would not need build steps to have a
clean way of doing it.

#!/JoePea