Proposal: Generate wrapper only when needed

Lately, Google Dart has been getting some well-deserved flack for a trivial "Hello, world" example generating thousands of lines of JS output. Meanwhile, though, CoffeeScript is generating 3 lines when it could be generating just 1. Since

```
console.log 'Hello, world!'
```

contains no scoped variables, I don't see any benefit to generating the output

```
(function() {
console.log('Hello, world!');
}).call(this);
```

instead of just

```
console.log('Hello, world!');
```

I propose that the wrapper only be added when it has an effect on scope. What do other folks think?